Ansys Blade Modeler

TurboSystem

ANSYS, Inc. Southpointe 275 Technology Drive Canonsburg, PA 15317 [email protected] http://www.ansys.com (T) 724-746-3304 (F) 724-514-9494

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Table of Contents Introduction to TurboSystem ..................................................................................................................... 1 TurboSystem Workflows ............................................................................................................................. 3 Geometry Sources .................................................................................................................................. 3 Mesh Sources ......................................................................................................................................... 3 Solution Sources ..................................................................................................................................... 3 Examples of TurboSystem Workflows ...................................................................................................... 4 Usage Notes for Specific Workflows ......................................................................................................... 5 Tips on using ANSYS Workbench ....................................................................................................... 5 Using BladeGen ................................................................................................................................ 6 Changing the Active Document in BladeGen ............................................................................... 6 Using BladeEditor ............................................................................................................................. 6 Loading versus Importing a BladeGen Geometry ......................................................................... 6 Restarting a BladeEditor Session ................................................................................................. 7 Modifying Spline Curves ............................................................................................................. 7 Adding a Hub Fillet to an Imported BladeGen Geometry ............................................................. 7 Creating a Full 360-Degree Fluid Zone for an Impeller .................................................................. 8 Using ANSYS TurboGrid .................................................................................................................... 8 Using ANSYS CFX .............................................................................................................................. 8 Connecting from a Turbo Mesh Cell ............................................................................................ 9 Changing the Geometry ............................................................................................................. 9 Quick Pump Tutorial ............................................................................................................................... 9 ANSYS BladeGen ....................................................................................................................................... 13 ANSYS BladeEditor ................................................................................................................................... 19 The BladeEditor User Interface .............................................................................................................. 19 Tree View and Details View .............................................................................................................. 19 Contour Sketch Management ......................................................................................................... 20 BladeEditor Toolbars ....................................................................................................................... 21 Feature Creation Toolbar ........................................................................................................... 21 Active Selection Toolbar ............................................................................................................ 23 Display Control Toolbar ............................................................................................................. 24 Angle and Thickness Views ............................................................................................................. 24 Angle View ............................................................................................................................... 24 Thickness View ......................................................................................................................... 25 User Preferences and Properties ...................................................................................................... 25 Blade Editing Features .......................................................................................................................... 26 Flow Path Contour Creation ............................................................................................................ 27 FlowPath Feature ............................................................................................................................ 28 Flow Cut ................................................................................................................................... 29 Camberline/Thickness Definition Feature ........................................................................................ 30 Importing and Exporting Angle Definition Data ........................................................................ 32 Importing and Exporting Thickness Definition Data ................................................................... 33 Converting Curves to Bezier or Spline ........................................................................................ 33 Converting Angle Definition Data ............................................................................................. 34 Forcing Interpolation of the Definition Data .............................................................................. 34 Blade Feature ................................................................................................................................. 34 Splitter Feature ............................................................................................................................... 36 Cloned Splitter ......................................................................................................................... 36 Independent Splitter ................................................................................................................ 36 Stage Fluid Zone Feature ................................................................................................................ 38 Throat Area Feature ........................................................................................................................ 39 Release 12.0 - © 2009 SAS IP, Inc. 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TurboSystem Importing Blades from ANSYS BladeGen ............................................................................................... 41 Loading and Modifying Blades from ANSYS BladeGen ........................................................................... 45 Using and Exporting Blades .................................................................................................................. 45 Export to Vista TF (.geo) .................................................................................................................. 46 Export as Meanline Data (.rtzt file) ................................................................................................... 47 Export to ANSYS TurboGrid ............................................................................................................. 48 Configuring the BladeModeler License .................................................................................................. 50 ANSYS TurboGrid ...................................................................................................................................... 53 ANSYS CFX-Pre ......................................................................................................................................... 57 ANSYS CFD-Post ........................................................................................................................................ 59 Vista TF ..................................................................................................................................................... 61 Vista TF User's Guide ............................................................................................................................. 61 Vista TF Setup Cell Properties .......................................................................................................... 62 Customizing the Vista TF Template Files ........................................................................................... 66 Vista TF Context Menu Commands .................................................................................................. 67 Vista TF Reference Guide ....................................................................................................................... 68 Running Vista TF from the Command Line ....................................................................................... 68 Input and Output Data Files for Vista TF ........................................................................................... 69 The Auxiliary File with the Default Name: vista_tf.fil ................................................................... 69 Overview of Input Files ............................................................................................................. 70 Overview of Output Files .......................................................................................................... 72 Specification of the Control Data File (*.con) .............................................................................. 74 Specification of the Geometry Data File (*.geo) .......................................................................... 83 Specification of Aerodynamic Data File (*.aer) ............................................................................ 91 Specification of Correlations Data File (*.cor) ............................................................................ 101 Specification of the Output Data File (*.out) ............................................................................. 111 Specification of the Text Data Files (*.txt) ................................................................................. 114 Specification of the CFD-Post Output Files (*.csv) ..................................................................... 116 Specification of Convergence History Data File (*.hst) .............................................................. 117 Software Limitations ..................................................................................................................... 118 Streamline Curvature Throughflow Theory .................................................................................... 118 The Equations ......................................................................................................................... 119 The Mean Stream Surface ....................................................................................................... 119 The Grid ................................................................................................................................. 120 Ductflow and Throughflow ..................................................................................................... 121 Iterative Solution Procedure .................................................................................................... 121 Initial Estimate ........................................................................................................................ 122 Radial Equilibrium Equation .................................................................................................... 122 Combination of Velocity Gradient and Continuity Equations .................................................... 122 Relaxation Factors ................................................................................................................... 123 Streamline curvature .............................................................................................................. 123 Equations for Enthalpy and Angular Momentum ..................................................................... 123 Boundary Conditions .............................................................................................................. 123 Empirical Data ........................................................................................................................ 124 Blade-to-blade Solution .......................................................................................................... 124 Spanwise Mixing .................................................................................................................... 124 Streamline Curvature Throughflow Theory: Bibliography ......................................................... 125 Appendices .................................................................................................................................. 126 Appendix A: A Note on Sign Convention for Angles and Velocities ............................................ 127 Definition of Blade Lean Angles ......................................................................................... 128 Definition of Meridional Streamline Inclination Angle or Pitch Angle .................................. 129 Definition of Blade Angle .................................................................................................. 129

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TurboSystem Appendix B: Example of a Control Data File (*.con) ................................................................... 130 Appendix C: Example of a Geometry Data File (*.geo) for a Radial Impeller ............................... 130 Appendix D: Example of an Aerodynamic Data File (*.aer) ........................................................ 132 Appendix E: Examples of Correlations Data Files (*.cor) ............................................................ 133 Appendix F: Troubleshooting .................................................................................................. 138 Input-output Errors ........................................................................................................... 139 Convergence .................................................................................................................... 140 Reverse Flow .................................................................................................................... 142 Choking ........................................................................................................................... 142 Computational Grid .......................................................................................................... 144 Other Numerical Issues ..................................................................................................... 145 Appendix G: The RTZTtoGEO Program ..................................................................................... 147 Index ........................................................................................................................................................ 151

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Introduction to TurboSystem TurboSystem is a set of software applications and software features for designing turbomachinery in the ANSYS Workbench environment. It consists of the following components: •

ANSYS BladeGen: a geometry creation tool that is specialized for turbomachinery blades. For details, see "ANSYS BladeGen" (p. 13).

•

ANSYS DesignModeler: a general purpose geometry preparation tool that is integrated in ANSYS Workbench. This CAD-like program is primarily used to prepare CAD geometry models for analysis by other ANSYS Workbench based tools. For details, see DesignModeler Help.

•

ANSYS BladeEditor: a plugin for DesignModeler for creating blade geometry. ANSYS BladeEditor provides the geometry link between BladeGen and DesignModeler, and therefore links BladeGen with other ANSYS Workbench based applications. For details, see "ANSYS BladeEditor" (p. 19).

•

ANSYS TurboGrid: a meshing tool that is specialized for CFD analyses of turbomachinery blade rows. For details, see "ANSYS TurboGrid" (p. 53).

•

ANSYS CFX-Pre: a general-purpose CFD preprocessor that has a turbomachinery setup wizard for facilitating the setup of turbomachinery CFD simulations. For details, see "ANSYS CFX-Pre" (p. 57).

•

ANSYS CFD-Post: a general-purpose CFD postprocessor that has features for facilitating the post-processing of turbomachinery CFD simulations. For details, see "ANSYS CFD-Post" (p. 59).

•

Vista TF: a streamline curvature throughflow program for the analysis of turbomachinery. This program enables you to rapidly evaluate radial blade rows (pumps, compressors and turbines) at the early stages of the design. For details, see "Vista TF" (p. 61).

For information about using TurboSystem in various workflows, see "TurboSystem Workflows" (p. 3).

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TurboSystem Workflows TurboSystem is a set of software applications and software features that help you to perform turbomachinery analyses in ANSYS Workbench. The software applications and features are listed in "Introduction to TurboSystem" (p. 1). This chapter describes the primary ways of using TurboSystem. The following topics are discussed: Geometry Sources Mesh Sources Solution Sources Examples of TurboSystem Workflows Usage Notes for Specific Workflows Quick Pump Tutorial

Geometry Sources The turbomachinery geometry is typically provided by one of the following cells: •

Blade Design cell of a BladeGen system

•

Geometry cell of a Geometry or Mesh system This can be based on an upstream Blade Design cell. If you want to pass the geometry to the Turbo Mesh cell of a TurboGrid system, you must use BladeEditor to export to ANSYS TurboGrid.

Mesh Sources The mesh is typically provided by one of the following cells: •

Turbo Mesh cell of a TurboGrid system

•

Mesh cell of a Mesh system

Solution Sources You can use one of the following systems to compute and report performance data: •

CFX component system Use a CFX component system to perform a CFD analysis.

•

Vista TF component system Use a Vista TF component system to perform a throughflow analysis.

•

Static Structural (ANSYS) analysis system Use a Static Structural (ANSYS) analysis system to compute stresses and strains due to fluid forces and centrifugal forces. Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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TurboSystem Workflows

Examples of TurboSystem Workflows This section shows examples of TurboSystem workflows, represented as connected systems in the Project Schematic view. Many other configurations are possible. CFD analysis of a centrifugal pump:

CFD analysis of a turbine stage:

Throughflow analysis and CFD analysis of a turbine stage:

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Tips on using ANSYS Workbench

Usage Notes for Specific Workflows This section describes TurboSystem-related workflow issues and recommended practices: Tips on using ANSYS Workbench Using BladeGen Using BladeEditor Using ANSYS TurboGrid Using ANSYS CFX

Tips on using ANSYS Workbench The following is a list of tips that you may find useful when working in ANSYS Workbench: •

Try right-clicking on different parts of the interface to see shortcut menus.

•

You may find Compact Mode to be useful. Select View > Compact Mode from the ANSYS Workbench to turn the Project Schematic view into a small, non-intrusive “title bar” menu or click that is always visible. To return to Full Mode, hover the mouse over the title bar, then, after the window has expanded, click Restore Full Mode

in the upper-right corner of the application window.

•

Use the Files view to determine which files were created for each cell/system. It is easiest to find files associated with a specific cell by sorting the view by Cell ID. This will sort the list by system and then by cell.

•

When selecting a system in the toolbox, ANSYS Workbench will highlight the cells in any systems already in the Project Schematic view to which a valid connection can be made. Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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TurboSystem Workflows •

Give unique meaningful names to all of your systems, especially if there are multiple systems of the same type.

Using BladeGen The following topic(s) are discussed: Changing the Active Document in BladeGen

Changing the Active Document in BladeGen If you want to replace the active document in BladeGen, then: 1.

Reset the corresponding Blade Design cell.

2.

Edit the Blade Design cell or right-click it and select Import Existing Case.

Note that opening a subsequent .bgd file in the same instance of BladeGen will not replace the model associated with the Blade Design cell.

Using BladeEditor The following topic(s) are discussed: Loading versus Importing a BladeGen Geometry Restarting a BladeEditor Session Modifying Spline Curves Adding a Hub Fillet to an Imported BladeGen Geometry Creating a Full 360-Degree Fluid Zone for an Impeller

Loading versus Importing a BladeGen Geometry There are two basic ways of transferring a BladeGen geometry into BladeEditor •

Importing If you import the geometry, the connection to the BladeGen geometry is maintained, and blade geometry changes must be made by editing the upstream Blade Design cell.

•

Loading If you load the geometry, native BladeEditor features are created to represent the complete geometry, the connection to the BladeGen geometry is lost, and all geometry changes must be made by editing the Geometry cell.

Linking from a Blade Design cell to a Geometry cell causes the BladeGen geometry to be imported into BladeEditor. The desired import options should be set in the Blade Design cell properties. (See Table 1: BladeGen Blade Design Cell Properties (p. 14) for more information.) After you make the link, the Geometry cell should be updated to process the imported geometry.

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Using BladeEditor

Note If you edit the Geometry cell before updating it, then the Import BGD feature details that are shown in BladeEditor may not accurately reflect the Blade Design cell properties. To refresh the Import BGD feature properties, click in BladeEditor. It is not recommended that you edit the Import BGD properties inside BladeEditor because they will be overwritten by the properties from the Blade Design cell the next time you update the Geometry cell. For details on importing BladeGen geometries, see Importing Blades from ANSYS BladeGen (p. 41). For details on loading BladeGen geometries, see Loading and Modifying Blades from ANSYS BladeGen (p. 45).

Restarting a BladeEditor Session If you want to clear a BladeEditor session while maintaining the link to the upstream cell, do not use the Start Over command from the File menu in BladeEditor. Doing so would erase the incoming data from any upstream connections — notably when there is an upstream link to a BladeGen system. Instead, return to the Project Schematic view, right-click the Geometry cell and select Reset from the shortcut menu. When you subsequently edit the Geometry cell, the upstream data is imported correctly.

Modifying Spline Curves When a spline is initially created, it is uniquely defined by its fit points. If you move any of the points, the spline may or may not be uniquely-defined, depending on the way in which you move the points: •

•

If you move a fit point by using the following procedure, the resulting spline will be uniquely defined: 1.

On the Sketching tab, click Spline Edit.

2.

Click the spline in the viewer to select it.

3.

Right-click the spline and select Drag Fit Point.

4.

Drag one or more fit points to adjust the shape of the spline.

If you move a fit point using the Drag tool on the Sketching tab, or if you change a parameter that controls a fit point location, the resulting spline will not be uniquely defined. Such a spline is usable, but if you want the spline to be uniquely defined by the position of the fit points, then: 1.

On the Sketching tab, click Spline Edit.

2.

Click the spline in the viewer to select it.

3.

Right-click the spline and select Re-fit Spline.

Adding a Hub Fillet to an Imported BladeGen Geometry Assuming that you have already created the hub when you initially imported the BladeGen model, you can add a hub fillet using the following procedure: 1.

Edit the Geometry cell.

2.

In BladeEditor/DesignModeler, in the feature tree, right-click the first feature that is listed below both the hub and blade features, then select Insert > Fixed Radius from the shortcut menu. This inserts a new Blend feature immediately above the feature that you right-click in the tree. Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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TurboSystem Workflows 3.

Select an edge along the intersection of a blade and the hub, for each edge that is to have a fillet of a specified size. You may need to use viewer toolbar icons to manipulate the view beforehand. If you cannot select an edge, confirm that the selection filter is set for selecting edges (the

4.

toolbar icon).

Select Extend to Limits from the toolbar.

This causes the selected edge to reach as far as possible around the blade. 5.

Click Apply beside the Geometry property in the details view.

6.

Set an appropriate value for the Radius property in the details view.

7.

Click

.

Creating a Full 360-Degree Fluid Zone for an Impeller Assuming that you have not created the fluid zone when you initially imported the BladeGen model, you can create a fluid zone for a full, 360° impeller model using the following procedure: 1.

View the Blade Design cell properties. To do this, right-click the Blade Design cell and select Properties from the shortcut menu.

2.

In the Properties view, ensure that Create All Blades is selected.

3.

Update the Geometry cell if required.

4.

Edit the Geometry cell.

5.

Create a Revolve feature using the master profile, and revolve it around the axis for the full 360° to generate the annulus volume.

6.

Use an Enclosure feature to subtract the solid impeller from the annulus to generate the desired full 360° fluid zone.

Using ANSYS TurboGrid The following is a list of tips that you may find useful when working with ANSYS TurboGrid: •

Session file playback in ANSYS TurboGrid in ANSYS Workbench is not supported. It is released as a beta feature. For more information about this feature, see the Beta Features section of the ANSYS TurboGrid release notes in the online help.

•

ANSYS Workbench units and appearance options are not passed to ANSYS TurboGrid.

Using ANSYS CFX The following topic(s) are discussed: Connecting from a Turbo Mesh Cell

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Quick Pump Tutorial Changing the Geometry

Note For more tips on using ANSYS CFX in ANSYS Workbench, please refer to the ANSYS CFX in ANSYS Workbench chapter of the ANSYS CFX online help, which is accessible from the Help menu in CFX-Pre.

Connecting from a Turbo Mesh Cell It is recommended that you connect the Turbo Mesh cell of a TurboGrid system to the Setup cell of a CFX component system rather than to the Setup cell of a Fluid Flow (CFX) system.

Changing the Geometry After setting up a turbomachinery simulation in a CFX component system, if you change topology or number of blades in the mesh, then refreshing or updating the CFX Setup cell (directly or indirectly) will fail to propagate the new information correctly. This will lead to incorrect results. To compensate, you can manually correct the number of blades in CFX-Pre by re-entering Turbo Mode (available from the Tools menu). In addition, the boundaries may need to be manually corrected in CFX-Pre. If you generate a turbo report in CFD-Post (the latter accessed by editing the Results cell), then subsequently make changes that affect the upstream solution, and then update the Results cell, the resulting turbo report will use the updated values for any variables (such as pressure and velocity) and expressions that it uses, but the report will continue to use the old turbomachinery data (such as the number of blades and the machine axis). After updating the solution, you will have to take one of the following actions to update the turbo report: •

•

If you have no work that needs to be preserved with respect to the Results cell, then: 1.

Reset the Results cell.

2.

Edit the Results cell.

3.

Load a turbo report.

If you have done work in CFD-Post but have no work that needs to be preserved with respect to the turbo report, then: 1.

Update the Results cell.

2.

Reload the turbo report.

This is slower than the previously-mentioned method because the update process includes an unwanted reprocessing of the old turbo report (with new results, but old turbomachinery data). However, because this method does not involve resetting the Results cell, any work you have done in CFD-Post is preserved (except for any modifications you have made to the original report).

Quick Pump Tutorial In this tutorial, you will quickly run through the steps required to simulate a water pump while using TurboSystem.

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TurboSystem Workflows

Designing the Blade and Creating the Mesh 1.

Open ANSYS Workbench and click File > Save As.

2.

Save the project as QuickPump in a suitable directory.

3.

In the Toolbox view, under Component Systems, double-click BladeGen. A new BladeGen system appears in the Project Schematic view.

4.

Double-click the Blade Design cell in the BladeGen system. BladeGen appears.

5.

Within BladeGen, create a new blade using Vista CPD by selecting File > New > Vista Centrifugal Pump Design.

6.

On the Geometry tab, change the number of blades from 6 to 7, then click Calculate. The pump design is updated and the results are displayed.

7.

Click Impeller Model.

8.

Exit BladeGen and return to the Project Schematic view.

9.

Right-click the Blade Design cell and select Create New Blade CFD Mesh. After some time, a mesh will be created.

Note If you receive an error message about licensing, click Tools > License Preferences and, in the dialog box on the Geometry tab, select ANSYS BladeModeler, click Move up, then click OK. You should then delete the Mesh system from the Project Schematic view before continuing. 10. Right click the Mesh cell of the Mesh system and select Transfer Data To New > CFX. A CFX system is added. The additional information requirements posed by the CFX system causes the Mesh cell to switch to an 'Update Required' state, as indicated by the

symbol.

11. Right-click the Mesh cell and select Update. 12. Double-click the Setup cell in the CFX system.

CFX-Pre appears.

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Setting up the Turbomachinery Simulation

Setting up the Turbomachinery Simulation You will use CFX-Pre in Turbo mode to set up physics and boundary conditions. In this case, you will specify the same rotational rate and mass flow as specified in Vista CPD. 1.

Click Tools > Turbo Mode.

2.

On the Basic Settings panel, set Machine Type to Pump, Rotation Axis to Z, and leave the other settings at their defaults.

3.

Click Next.

4.

On the Component Definition panel, double-click R1 and set the following values: Setting

Value

Component Type > Type

Rotating

Component Type > Value

1450 [rev min^-1]

Wall Configuration

(Selected)

Wall Configuration > Tip Clearance at Shroud

Yesa

a Although, in this case, the geometry and mesh do not model the tip clearance, specifying a tip clearance at the shroud causes the entire shroud to be treated as being stationary (via a counter-rotating wall in the rotating frame); otherwise, the entire shroud would be treated as being a rotating wall (stationary in the rotating frame).

Leave the other settings at their defaults. 5.

Click Next.

6.

On the Physics Definition panel, set the following values: Setting

Value

Fluid

Water

Model Data > Reference Pressure

1 [atm]

Inflow/Outflow Boundary Templates > P-Total Inlet Mass Flow Outlet

(Selected)

Inflow/Outflow Boundary Templates > P-Total

0 [atm]

Inflow/Outflow Boundary Templates > Mass Flow

Per Machine

Inflow/Outflow Boundary Templates > Mass Flow Rate

77.8 [kg s^-1]

Inflow/Outflow Boundary Templates > Flow Direction

Normal to Boundary

Solver Parameters > Advection Scheme

High Resolution

Solver Parameters > Conver- Physical Timescale gence Control

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TurboSystem Workflows Setting

Value

Solver Parameters > Physical 1e-2 [s]a Timescale a

The time scale is approximately 1/(rotation speed [rad/s]). This gives a much more aggressive timescale than the default, for faster convergence.

Leave the other settings at their defaults. 7.

Click Next.

8.

On the Interface Definition panel, verify that the periodic interface is set correctly. To do this, click R1 to R1 Periodic 1 in the tree view and then examine the associated settings (shown in the lower portion of the panel) and highlighted regions in the viewer. If no regions appear highlighted in the viewer, ensure that highlighting is turned on in the viewer toolbar.

9.

Click Next.

10. On the Boundary Definition panel, verify that each boundary is set correctly. To do this, click a boundary listed in the tree view and then examine the associated settings and highlighted regions. 11. Click Next. 12. On the Final Operations panel, leave the operation set to Enter General Mode and click Finish. 13. Return to the Project Schematic view. 14. Right-click the Solution cell and select Update. After some time, a CFD solution will be generated. If the progress indicator is not visible, you can display or, to see detailed output, right-click the Solution cell and select Display

it by clicking Monitors. 15. Double-click the Results cell. CFD-Post appears.

Viewing the Turbo Report To see a report for the pump performance: 1.

Click File > Report > Load 'Pump Impeller Report' Template.

2.

Click the Report Viewer tab.

Note that if you have visited the Report Viewer tab before loading the template, or have otherwise made any changes to the report definition after first viewing the report, you need to click Viewer to update the report as displayed.

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in the Report

ANSYS BladeGen ANSYS BladeGen is a geometry creation tool that is specialized for turbomachinery blades. BladeGen has its own documentation that can be accessed through the user interface, or by browsing the installation directory. The main documentation, “ANSYS BladeGen User's Guide”, is available from the Help menu in BladeGen. There, you will find general help, tutorials, and help on a series of Vista programs which run inside BladeGen: •

Vista CCD (for centrifugal compressors)

•

Vista CPD (for centrifugal pumps)

•

Vista RTD (for radial inflow turbines)

•

Vista AFD (for axial fans)

Note Another Vista program, Vista TF, is for throughflow analyses in turbomachinery. It has a reference guide named "Vista TF Reference Guide" that is in this set of documentation. You can access it by clicking the following link: Vista TF Reference Guide (p. 68). To launch BladeGen from ANSYS Workbench, add the BladeGen component system to your project schematic, then edit the Blade Design cell of that system. The Blade Design cell has properties that need to be configured in order to transfer the blade geometry from BladeGen to BladeEditor. This transfer is represented by a link that connects a Blade Design cell to a Geometry cell. A sample of the cell properties is shown in Figure : Properties of the BladeGen Blade Design Cell (p. 13).

Figure: Properties of the BladeGen Blade Design Cell

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ANSYS BladeGen Table 1: BladeGen Blade Design Cell Properties (p. 14) describes each of the cell properties. These are related to the properties of the ImportBGD feature in BladeEditor (described at Table 3: Properties for the Import BGD File Feature (p. 42)).

Table 1 BladeGen Blade Design Cell Properties Group

Name

Description

Import Options

Create Hub*

If this property is selected, then BladeEditor will create a HubProfile sketch for the non-flow path hub geometry, and will create a revolved body feature called HubBody.

Create All Blades

If this property is selected, then BladeEditor will create all the blades using the number of blades specified in the BladeGen model. If this property is not selected, then only the first blade will be created.

Merge Blade Topo- If this property is not selected, then logy BladeEditor will create the blade with four faces corresponding to the leading edge, pressure side, trailing edge and suction side. This can make it easier to create a structural mesh for the blades in the Mechanical application. If this property is selected, then the blade faces will be merged where they are tangent to one another. Blade Loft Direction

If this property is set to Streamwise, then BladeEditor will loft the blade surfaces in the streamwise direction through curves that run from hub to shroud. This is the default because the surface is more well defined, especially for flank-milled blades. If this property is set to Spanwise, then BladeEditor will loft the blade surfaces in the spanwise direction through the blade profile curves.

Shroud Clearance

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This property specifies whether a shroud clearance is created. If None is selected, then no shroud clearance is created. To create a shroud clearance, choose either Relative Layer or Absolute Layer. The blade(s) will be trimmed off at the selected BladeGen output layer, and the layer contour will be created in the LayerProfile sketch.

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ANSYS BladeGen Group

Name

Description If Relative Layer is selected, then the selected Layer Number is relative to the shroud layer, e.g., 1 implies the first layer closest to the shroud layer, 2 implies the second closest layer to the shroud, etc. If Absolute Layer is selected, then the selected layer index counts up from the hub layer, which is zero.

Create Fluid Zone*

If this property is selected, then BladeEditor will create a StageFluidZone body for the flow passage, and an Enclosure feature to subtract the blade body. The resulting Enclosure can be used for a CFD analysis of the blade passage.

Create Named Selections*

If this property is selected, then BladeEditor will create NamedSelections (regions) for the typical faces of the blade passage, i.e., Blade, Hub, Shroud, Inflow, Outflow, PeriodicA and PeriodicB. These NamedSelections can be used as selection groups in other ANSYS Workbench applications, e.g., as regions in CFX-Mesh. Note that this property is available only if Create Fluid Zone is selected.

Blade Extension (%)

This property defines the surface extension length (as a percentage of the average hub to shroud distance) for the blade surfaces. These surfaces are extended and then trimmed to the MasterProfile sketch to ensure that the blade solid correctly matches the hub and shroud contours.

Periodic Surface Extension (%)

This property defines the surface extension length (as a percentage of the average hub to shroud distance) for the periodic surfaces. These surfaces are extended to ensure that the StageFluidZone is properly cut.

Periodic Surface Style

This property specifies the style of the periodic interface surfaces. If Three Pieces is selected, then the periodic surface is created in three con-

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ANSYS BladeGen Group

Name

Description nected pieces: one upstream of the blade, one within the passage, and one downstream of the blade. This style can better accommodate highly curved or twisted blades, and is similar to the ANSYS TurboGrid style of periodic surface. If One Piece is selected, then the periodic surface is created as a single surface. Note that this property is available only if Create Fluid Zone is set to Yes.

* These properties will only apply when you initially import the model. Any subsequent changes to these properties will not be propagated to downstream cells upon updating the latter. Once the ImportBGD feature has been created (for example, by updating the Geometry cell), changing the following Blade Design cell properties will have no effect: •

Create Hub

•

Create Fluid Zone

•

Create Named Selections

Note In order to facilitate the use of a BladeGen model in another application (such as BladeEditor or ANSYS TurboGrid), you should always ensure that the model units are set. When you create a new BladeGen model (File > New > BladeGen Model), the default units are always “Unknown” (regardless of ANSYS Workbench preferences). In this case, select Model > Properties from the BladeGen main menu and set Model Units in the Model Property Dialog. You can access a context menu for the Blade Design cell in the BladeGen component system by right-clicking the cell. Most of the commands that are available are standard, and are described in Systems and Cells. The context menu commands that are specific to the Blade Design cell are described in Table 2: Context Menu Commands Specific to the BladeGen Blade Design Cell (p. 16).

Table 2 Context Menu Commands Specific to the BladeGen Blade Design Cell Command

Description

Edit

This command opens BladeGen. If the cell is up to date, then BladeGen will load the associated BladeGen model.

Import Existing Case

This command opens a file browser for selecting a .bgd file. This command is only available if the cell is in the Edit Required state. If this command is not available due to having already selected a .bgd file, and you want to make the command available so

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ANSYS BladeGen Command

Description that you can select a different .bgd file, then choose the Reset command in the context menu.

Create New Blade CFD Mesh This command creates a linked Mesh system and generates a mesh for the associated BladeGen model. This command is available only if the cell is up to date.

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ANSYS BladeEditor ANSYS BladeEditor is a plugin for ANSYS DesignModeler for creating, importing, and editing blade geometry. Using BladeEditor, you can create a blade from scratch. You can also import a blade from ANSYS BladeGen. Once you have a blade in DesignModeler, you can use it as you would any geometry created in DesignModeler. In addition, you can use BladeEditor to export the geometry for use in ANSYS TurboGrid (a meshing tool) and Vista TF (a throughflow analysis tool). The following topics are discussed: The BladeEditor User Interface Blade Editing Features Importing Blades from ANSYS BladeGen Loading and Modifying Blades from ANSYS BladeGen Using and Exporting Blades Configuring the BladeModeler License

The BladeEditor User Interface The BladeEditor user interface extends the DesignModeler user interface in the following ways: •

There are new feature types aimed at creating a blade and flow passage.

•

There is a set of toolbar icons, most of which are used to create the new feature types.

•

There are new views associated with some of the feature types.

•

There are new context menu commands associated with the new views.

The following topics will be discussed: Tree View and Details View Contour Sketch Management BladeEditor Toolbars Angle and Thickness Views User Preferences and Properties

Tree View and Details View As with DesignModeler features, the primary user control of the new blade geometry features is through the tree view and details view. The tree view shows the list of the features in the current model, and provides a mechanism for you to select a feature for inserting, editing, or deleting. The tree view also shows the order of operations in which DesignModeler will generate the model (top to bottom), and the feature dependencies.Figure : Tree View (p. 20) shows an example of the tree view diagram with the sketches (HubContour1), FlowPath (FlowPath1), CamThkDef (IGVCam1), and Blade (IGV) features for two blade rows.

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ANSYS BladeEditor

Figure: Tree View

You might want to temporarily suppress various features to speed up the regeneration time. This can be managed in DesignModeler by right-clicking the feature in the tree view and selecting “Suppress”. Note that suppressing a feature also suppresses all dependent features below it. Sketches cannot be suppressed; they can only be hidden or deleted. When you click a contour sketch in the tree view, the sketch will be highlighted in the 3D viewer. When you click on a camberline definition, the corresponding FlowPath layer contour will be highlighted in the 3D viewer, and the angle and thickness views will be displayed for this definition. Any changes made to the sketches or camberline definitions will be immediate. However, updates to the dependent FlowPath or Blade features will happen only when you subsequently click the “Generate” button.

Contour Sketch Management The contour sketches are managed just as normal sketches are managed in DesignModeler. To modify a meridional contour, you should first select the sketch in the tree view and then click the “Sketching” tab to open the sketch toolbox. If you already have the sketch toolbox open, you can select a different active sketch from the toolbar drop-down list. For models with many different sketches, and for switching between editing one contour or another, this could be tedious. For this reason, it is possible to modify or delete existing edges in a sketch that is not the active sketch as long as it belongs to the same plane as the active sketch. However, newly created edges are added only to the active sketch, so it is imperative that you have the active sketch selected appropriately when creating new edges.

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BladeEditor Toolbars

BladeEditor Toolbars BladeEditor utilizes three separate toolbars: one for feature creation, one for selection, and one for display control. The following topics are discussed Feature Creation Toolbar Active Selection Toolbar Display Control Toolbar

Feature Creation Toolbar The feature creation toolbar has icons for the BladeEditor specific features that can be added to the model (and that appear in the tree view). The following icons exist in this toolbar: Icon

Description

Import BGD

Creates an ImportBGD feature, which is used to import a BladeGen file and construct a solid model of the blade and optionally the hub and fluid zone. The flow path and blade shape cannot be edited in BladeEditor, but the import can be refreshed if there are any changes to the BladeGen file. For details, see Importing Blades from ANSYS BladeGen (p. 41).

Load BGD

Loads a BladeGen file and constructs the FlowPath, CamThkDef, Blade, and Splitter features so that the flow path and blade shape may be edited in BladeEditor.

FlowPath

Creates a flow path (FlowPath) feature, which is used to define the flow path for blade geometry (that is, the meridional shape of the passage). For details, see FlowPath Feature (p. 28).

CamThkDef

Creates a camberline/thickness (CamThkDef ) feature (a blade profile), which is used to construct a blade geometry. For details, see Camberline/Thickness Definition Feature (p. 30).

Blade

Creates a blade (Blade) feature, which is used to create the blade bodies. For details, see Blade Feature (p. 34).

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ANSYS BladeEditor Icon

Description

Splitter

Creates a splitter (Splitter) feature, which is used to create the splitter bodies. For details, see Splitter Feature (p. 36).

VistaTFExport

Creates a Vista TF export (VistaTFExport) feature for exporting the flow path and blade geometry to the Vista TF through flow analysis tool. For details, see Export to Vista TF (.geo) (p. 46).

ExportPoints

Creates an ExportPoints feature for exporting blade point data to TurboGrid or to a meanline file. For details, see Export to ANSYS TurboGrid (p. 48) and Export as Meanline Data (.rtzt file) (p. 47).

StageFluidZone

Creates a stage fluid zone (StageFluidZone) feature for generating the blade passage bodies. The stage fluid zone is a 3D fluid region to support CFD analyses. For details, see Stage Fluid Zone Feature (p. 38).

ThroatArea

Creates a throat area (ThroatArea) feature for calculating the blade throat area. For details, see Throat Area Feature (p. 39).

Preferences

Opens the BladeEditor preferences in the details view. For details, see User Preferences and Properties (p. 25).

Note that, because of limitations in the FlowPath, CamThkDef, and Blade features, the ‘Load BGD’ feature supports loading BladeGen files with the following restrictions: •

Model Only the ‘Angle/Thickness’ mode is supported.

•

If loading multiple BladeGen files, the Beta Definition, ‘from Axial’ or ‘from Tangential’, must be consistent for all files.

•

Layers Only specified span fraction layers are supported. The Spanwise Calculation mode must be ‘Geometric’.

•

Angle Definition Only Theta and/or Beta definitions are supported, not End Angle.

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BladeEditor Toolbars Only General and Ruled Element spanwise distributions are supported. At least one angle definition must exist on either the hub or shroud layer. The Angle View Data Location must be 'Meanline'. •

Thickness Definition Only the 'Normal to Meanline on Layer Surface' thickness data type is supported. The 'vs. Cam' and '% Cam vs. % Cam' thickness specifications are not supported. Only the General spanwise distribution is supported At least one thickness definition must exist on either the hub or shroud layer.

•

Meridional Profile Only the 'Design Profile' is supported.

Active Selection Toolbar The selection of the “active” angle and thickness view utilizes a toolbar similar to the sketch selection functionality. The toolbar consists of two combo boxes: one for the FlowPath/Blade selection and one for the layer selection. The first combo box will enable you to select from all of the currently defined FlowPath and Blade features, while the second combo box will enable you to select from the available layers defined on the active FlowPath. For example, for a model that contains two FlowPath features (FlowPath1 and FlowPath2) with one Blade feature defined on FlowPath1 and a Blade feature and Splitter feature defined on FlowPath2, the combo box would list the following: FlowPath1 FlowPath1 Blade1 FlowPath2 FlowPath2 Blade2 FlowPath2 Splitter2 The FlowPaths and Blades are shown separately because the CamDef feature is defined in the context of both the FlowPath and the Blade, and therefore the view is context-specific. Assuming there are five layers in the selected FlowPath/Blade, the Layer combo box would list the following: Layer 1 Layer 2 Layer 3 Layer 4 Layer 5 Alternatively, if CamDef features were defined on layers 1 and 5, then the Layer combo box would list the following:

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ANSYS BladeEditor Layer 1 CamDef1 Layer 2 Layer 3 Layer 4 Layer 5 CamDef2

Display Control Toolbar The display control toolbar enables you to control display properties such as the angle/thickness graph visibility and graph view actions such as “zoom fit”, etc.

Angle and Thickness Views The Angle and Thickness Views let you see and modify the Camberline/Thickness definitions. These views have behavior similar to the views in BladeGen. Both views present the data for the active CamDef feature. See Active Selection Toolbar (p. 23) for more details on how the active CamDef feature is selected. If the Blade feature or any of its parent features have been modified, the curves shown in the angle/thickness views, when displayed under the Blade feature, are updated when the model is regenerated. The following topics are discussed: Angle View Thickness View

Angle View The angle view displays a graph of the Theta and Beta angle definition for the selected CamDef feature. Within this view, you can: •

Access a shortcut menu by right-clicking the mouse.

•

Drag the control points defining the Theta/Beta curve (left-click on a control point and drag with the mouse).

•

Change the angle type: Theta or Beta (context menu).

•

Change the curve type (context menu).

•

Insert or delete points (context menu).

•

Set control point coordinates (double-click a control point and edit the coordinate values in a dialog box).

•

View the coordinates of any location on a curve (hold the Ctrl key and left click any control point or line segment of a curve).

•

Show all defining Theta/Beta curves in the current view (context menu).

•

Show the second angle curve (beta or theta) in the current view (context menu).

•

Pan the view (right-click and drag).

•

Zoom in and out (middle-click and drag).

•

Zoom in via a zoom box (hold the Alt key and left-click and drag from the top-left corner to the bottomright corner of a rectangular region; drag in the opposite direction to re-fit the view).

•

Change the x-axis display type: m, m’, %m, or %m’ (context menu).

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User Preferences and Properties •

Read angle data points from a file or save points to a file (context menu). In a crude way, this enables copying and pasting data from one CamDef feature to another, or to and from an external application, e.g. a spreadsheet.

•

Convert the selected curve segment to a Bezier or spline curve of the specified order (context menu).

Note When the meridional contours are changed, the angle data points are scaled relative to the percent m’-coordinate (% m-prime).

Note X-axis value behaviour: preference used as default. Change of x-axis value will affect all layers viewed for a given Blade feature.

Thickness View The thickness view displays a graph of the thickness definition for the selected CamDef feature. Within this view, you can: •

Drag the points defining the thickness curve (mouse)

•

Change the curve type: Bezier, cubic spline, piecewise-linear (context menu)

•

Insert or delete points (context menu)

•

Show all defining thickness curves in the current view (context menu)

•

Zoom/Pan the view (mouse)

•

Change the x-axis display type: m, m’, %m or %m’ (context menu)

•

Read thickness data points from a file or save points to a file (context menu)

•

Convert selected curve segment to Bezier or spline curve of specified order (context menu)

Note When the meridional contours are changed, the thickness data points are scaled relative to the percent m-coordinate (% m).

Note X-axis value behavior: preference used as default. Change of x-axis value will affect all layers viewed for a given Blade feature.

User Preferences and Properties The model properties are listed in the details view for the root node (along with the DesignModeler file properties.) Model properties are saved with the .agdb file. These properties include: •

Length Tolerance - Sketch edge tessellation tolerance in current length unit

•

Angle Tolerance – Angle graph tolerance in degrees

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ANSYS BladeEditor •

Beta definition (axial or tangential)

•

Angle View – x-axis type

•

Thickness View – x-axis type

•

Show Advanced Properties – this specifies whether the advanced parameters or expert parameters are shown in the details view. This only applies to specific features, such as the Blade and Splitter.

Blade Editing Features The BladeEditor toolbar icons related to creating/editing a blade are: Icon

Description

FlowPath

Creates a flow path (FlowPath) feature, which is used to define the flow path for blade geometry (that is, the meridional shape of the passage). For details, see FlowPath Feature (p. 28).

CamThkDef

Creates a camberline/thickness (CamThkDef ) feature (a blade profile), which is used to construct a blade geometry. For details, see Camberline/Thickness Definition Feature (p. 30).

Blade

Creates a blade (Blade) feature, which is used to create the blade bodies. For details, see Blade Feature (p. 34).

Splitter

Creates a splitter (Splitter) feature, which is used to create the splitter bodies. For details, see Splitter Feature (p. 36).

VistaTFExport

Creates a Vista TF export (VistaTFExport) feature for exporting the flow path and blade geometry to the Vista TF through flow analysis tool. For details, see Export to Vista TF (.geo) (p. 46).

ExportPoints

Creates an ExportPoints feature for exporting blade point data to TurboGrid or to a meanline file. For details, see Export to ANSYS TurboGrid (p. 48) and Export as Meanline Data (.rtzt file) (p. 47).

StageFluidZone

Creates a stage fluid zone (StageFluidZone) feature for generating the blade passage bodies. The stage fluid zone is a 3D fluid region to support CFD analyses. For

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Flow Path Contour Creation Icon

Description details, see Stage Fluid Zone Feature (p. 38).

ThroatArea

Creates a throat area (ThroatArea) feature for calculating the blade throat area. For details, see Throat Area Feature (p. 39).

The following topics will be discussed: Flow Path Contour Creation FlowPath Feature Camberline/Thickness Definition Feature Blade Feature Splitter Feature Stage Fluid Zone Feature Throat Area Feature

Flow Path Contour Creation The main elements of a multi-blade row machine are the flow path and the individual blade rows, as shown in Figure : Flow Path and Blade Row Concepts (p. 27).

Figure: Flow Path and Blade Row Concepts

The first step in creating new blade row geometry is creating the flow path contours that define the hub, shroud, inlet and outlet. The flow path contours are defined by sketch edges, which can be created using the existing DesignModeler sketch tools. Each contour (hub, shroud, etc.) should be defined in a separate sketch. This implicitly identifies all the edges belonging to a given contour. All contour sketches are expected to lie on the same Plane feature. Not only will this guarantee that the contours are coplanar, it will enable you to apply constraints and dimensions between sketches.

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ANSYS BladeEditor

Note •

Contour sketches must be created on the (global) ZX-plane. The local X and Y axes on the sketch plane correspond to the global Z and X axes, respectively. The local X axis corresponds to the machine axis and the local Y axis corresponds to the radial coordinate axis. Consequently, all flow contours in the sketch must have positive Y coordinates.

•

It is advisable that you turn off the sketch global autoconstraint setting. Click the Sketching tab, click the Constraints toolbox, click Auto Constraints and clear the Global check box. Having this global constraint turned on may cause undesirable constraints to be added to the LayerContour edges.

•

The hub, shroud, inlet, and outlet contour end points must be coincident.

FlowPath Feature The FlowPath feature specifies the flow path. The contour sketches described in Flow Path Contour Creation (p. 27) are used in the definition of this feature. The FlowPath feature also creates the constant-spanfraction layers used to define the blade profiles, and automatically creates the LayerContour sketch, which shows the locations of the layers. The feature properties are listed in the table below. Note that all items under each bold heading in the table are grouped under that heading. Details of [Feature Name] FlowPath

[Name]

Machine Type

[Pump | Centrifugal Compressor | Axial Compressor | Fan | Radial Turbine | Axial Turbine | Hydraulic Turbine | Other | Undefined]

Theta Direction

[Right-handed | Left-handed]

Hub Contour

[Sketch selection]

Shroud Contour

[Sketch selection]

Inlet Contour

[Sketch selection]

Outlet Contour

[Sketch selection]

Hub Cut?

[Yes | No]

(If Hub Cut = Yes)

[Sketch selection]

Hub Cut Shroud Cut?

[Yes | No]

(If Shroud Cut = Yes)

[Sketch selection]

Shroud Cut Number of Layers

Implicitly defined number of layers

Layer: 1 Layer Type

Fixed Span

Span Fraction

0

Layer: 2

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FlowPath Feature Layer Type

Fixed Span

Span Fraction

[0 < Value < 1]

Layer: 3 Layer Type

Fixed Span

Span Fraction

[0 < Value < 1]

Layer: 4 Layer Type

Fixed Span

Span Fraction

1

The Machine Type is used by downstream applications, for example in CFD-Post, for determining the appropriate default post-processing report. The Theta Direction specifies the interpretation of the theta direction for the CamDef angle definitions. The theta direction can be specified as either right-handed or left-handed relative to the direction of the global z-axis (the machine axis). By default, the flow path starts with two layers: one for the hub and one for the shroud. You can insert or delete layers using a shortcut menu in the details view. Layers on which CamDef features are defined cannot be deleted. The first and last layers must be at span fractions of 0 and 1, respectively; these will always be created and cannot be deleted or changed. A given blade does not need to have defined profiles on all layers. The layers are defined in the context of the FlowPath feature for consistency between blade rows. The only Layer Type in version 12 is Fixed Span. This requires that you specify the span fraction for the given layer. You can create the FlowPath feature automatically via a BladeGen import, or manually. In either case, you can change the sketch selections once the feature has been created. You must ensure that the contours are properly connected to form a closed loop. This means that the endpoints of adjacent contours must be coincident. In the tree view, the parent sketches (HubContour, ShroudContour, etc.) and child sketch (LayerContour) should appear as sub-features of the FlowPath feature. These sketches will also appear under the parent meridional plane. The following topic will be discussed: Flow Cut

Flow Cut The FlowPath feature has optional hub cut and shroud cut properties to support trimming the flow path for a 'flow cut'. An example is if you have a base centrifugal compressor blade design that is used for a range of compressors. In this case, the FlowPath and Blade features would define the base blade geometry. You then wish to use the same blade but in a different size compressor, so the blade height needs to be trimmed. The flow cut would be used to define the final flow path boundaries, and would trim the height of all blades in the flow path. The flow cut affects all blades that reference the flow path. The flow cut properties take as input the sketch contours that define the flow cut. The additional feature properties are in a group below the Outlet Contour property. The property group is defined below. To make best use of this feature, sketches should support the reading of external point data, in particular point data exported from CFD-Post. This lets you choose a flow “streamline” from a Vista TF or CFX analysis

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ANSYS BladeEditor and use it to trim the flow path. Currently, creating spline curves from external point data is only supported via script.

Camberline/Thickness Definition Feature The Camberline/Thickness Definition (CamDef ) feature provides the angle and thickness distribution on a selected layer contour. This definition is a child of the FlowPath feature and a parent of the Blade feature. The angle and thickness distributions are specified versus normalized coordinates corresponding to 0% at the leading edge and 100% at the trailing edge. A CamDef feature can be referenced by more than one Blade feature. Also, a CamDef feature can be copied from one layer to another. Each CamDef feature will appear as a sub-feature of the parent FlowPath in the tree view. When a CamDef feature is referenced by a Blade, it will also appear as a sub-feature for that Blade. This is consistent with the tree view behavior for sketches, which provide a similar function to the CamDef features. The CamDef feature properties are as follows: Details of [Feature Name] Camberline Definition

[Feature Name]

Flow Path

[FlowPath feature selection]

Layer Number

[Index Value]

Camberline Details Angle Definition?

[Yes | No]

Angle Definition Type

[Theta | Beta]

(For Beta definition only)

[Leading Edge | Trailing Edge]

Theta Reference Theta @ LE

[Value]

or Theta @ TE

[Value]

Angle Data Location

[Camberline | Side 1 | Side 2]

[Parameter List]

[Parameter Values]

Thickness Details Thickness Definition?

[Yes | No]

Thickness Definition Type

[Normal to Cambersurface | Normal to Camberline on Layer surface | Tangential on Layer surface]

The angle and thickness data that is associated with a CamDef feature is displayed in the angle/thickness graph view.

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Camberline/Thickness Definition Feature

The CamDef feature saves the angle data as % m-prime and the thickness data as % m. After a CamDef is applied to the portion of a layer between LE and TE of a blade/splitter, the local angle data and thickness data are created for the blade/splitter. These local data are represented as m-prime and m values which are converted from % m-prime and % m. If the Angle Definition Type is set to Theta, then the specified angle curve is used as the theta definition for the camberline. If the Angle Definition Type is set to Beta, then the angle curve is used as the Beta definition, and the theta definition is derived by integrating the Beta curve with the specified Theta Reference. The Theta Reference can be specified at either the leading edge or the trailing edge of the blade for which the camberline is applied. When a CamDef feature is selected on the feature tree, its angle data will be displayed on the angle graph and its thickness data will be displayed on the thickness graph. When the data in angle or thickness graph pane is modified, the data inside the CamDef feature will be changed to reflect the modification. Also, if any blade/splitter refers to the CamDef feature, all these blade/splitter should update their local angle/thickness data. If you select 'No' for the Angle Definition or Thickness Definition parameter, then no curve data for this definition will be available for editing in the graph view, and this definition will be ignored in the corresponding angle or thickness surface calculation. Furthermore, if the selected CamDef feature is a sub-feature to a Blade, then the graph view will show the interpolated angle or thickness data for this blade, otherwise

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ANSYS BladeEditor no data will be shown in the graph. The interpolated data is for display only and cannot be edited; the context menu commands for editing are hidden in this case. If you subsequently select 'Yes' for the Angle Definition or Thickness Definition parameter, then the curve data will be initialized by interpolation if possible, otherwise it will be initialized to default data (two points). Interpolation will occur if the selected CamDef feature is a sub-feature to a Blade, so that the data can be interpolated from the blade definition. If the CamDef feature is reference by more than one blade, then the blade that is selected (above the CamDef feature) will be used to interpolate the data. If you want to insert a CamDef feature into an existing Blade feature without initially affecting the shape of the blade, the ‘Insert/Interpolate Camberline’ operation can be used. Multi-select a new CamDef feature along with the Blade feature, right-click, and select ‘Insert/Interpolate Camberline’. The angle and thickness data of the selected CamDef feature will then be updated by interpolating from the existing blade. If you specify a curved leading or trailing edge contour, you must have at least three angle and/or thickness defining camberlines to create the desired blade shape. Furthermore, if you specify a cut-off leading or trailing edge and you do not have sufficient camberlines to follow the edge curvature, then the cut-off operation will fail. Adding additional camberline definitions (especially where the leading/trailing edge curve deviates the most from the blade shape) should fix this problem. The following topics are discussed: Importing and Exporting Angle Definition Data Importing and Exporting Thickness Definition Data Converting Curves to Bezier or Spline Converting Angle Definition Data Forcing Interpolation of the Definition Data

Importing and Exporting Angle Definition Data There is an import/export points mechanism for the Angle Definition to support the manipulation of the Angle Definition points outside of BladeEditor, and to provide a means to read data from a file produced externally. In the Angle View, the context menu operation 'Read Points' lets you replace the active curve data points from the data in a text file called a '.ha' file. The context menu operation 'Save Points' lets you save the active data points to a '.ha' text file. These options are available only if the Angle Definition is active, i.e. set to 'Yes'. The first line in the '.ha' file specifies the number of points. Subsequent lines in the file, one for each data point, contain the point coordinate values 'h, a', where 'h' is the horizontal or x-axis value and 'a' is the angle value. The point coordinates correspond to the defining points for the angle definition curve, which may be either Theta or Beta, in degrees, versus m-prime, % m-prime, m or % m. When reading the '.ha' file, the data point coordinates will be interpreted based on the Angle Definition Type and the selected x-axis type. If the Angle Definition Type is set to Theta, then the angle values will be interpreted as Theta values. Otherwise, the angle values will be interpreted as Beta values. If the x-axis is set to m-prime or % m-prime, then the 'h' coordinates for the data points will be treated as % m-prime values, and the values will be normalized based on the first and last data points so that the values start at zero and end at 100%. If the x-axis is set to m or % m, then the 'h' coordinates for the data points will be converted to m values by normalizing based on the first and last data points and then multiplying by the maximum m on the layer. These values will then be converted to % m-prime. The existing angle curve data for all segments will be replaced by a single curve segment with the data from the '.ha' file, and the curve type will be set to 'cubic spline'. When you choose 'Save Points', the defining points for all curve segments will be written sequentially to the file starting with the leading edge point and ending at the trailing edge point. The 'h' coordinates will 32

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Camberline/Thickness Definition Feature be written in the value corresponding to the selected x-axis type. If the Angle Definition Type is set to Theta, then the Theta values will be written as the angle values. Otherwise, the Beta values will be written as the angle values. You can select the x-axis scale as m-prime, m, or % m only if the selected CamDef feature is defined in the context of a Blade feature.

Importing and Exporting Thickness Definition Data There is an import/export points mechanism for the Thickness Definition to support the manipulation of the Thickness Definition points outside of BladeEditor, and to provide a means to read data from a file produced externally. In the Angle View, the context menu operation 'Read Points' lets you replace the active curve data points from the data in a text file called a '.ht' file. The context menu operation 'Save Points' lets you save the active data points to a '.ha' text file. These options are available only if the Thickness Definition is active, i.e. set to 'Yes'. The first line in the '.ht' file specifies the number of points. Subsequent lines in the file, one for each data point, contain the point coordinate values 'h, t', where 'h' is the horizontal or x-axis value and 't' is the thickness value. The point coordinates correspond to the defining points for the thickness definition curve in the length unit being used in DesignModeler, versus m-prime, % m-prime, m or % m. When reading the '.ht' file, the data point coordinates will be interpreted based on the selected Thickness Definition Type and the x-axis type. If the x-axis is set to m or % m, then the 'h' coordinates for the data points will be treated as % m values, and the values will be normalized based on the first and last data points so that the values start at zero and end at 100%. If the x-axis is set to m-prime or % m-prime, then the 'h' coordinates for the data points will be converted to m-prime values by normalizing based on the first and last data points and then multiplying by the maximum m-prime on the layer. These values will then be converted to % m. The existing thickness curve data for all segments will be replaced by a single curve segment with the data from the '.ht' file, and the curve type will be set to 'cubic spline'. When you choose 'Save Points', the defining points for all curve segments will be written sequentially to the file starting with the leading edge point and ending at the trailing edge point. The 'h' coordinates will be written in the value corresponding to the selected x-axis type, while the thickness coordinates will be written in the value corresponding to the selected Thickness Definition Type. You can select the x-axis scale as m-prime, m, or % m only if the selected CamDef feature is defined in the context of a Blade feature.

Converting Curves to Bezier or Spline This feature lets you convert a curve segment in either the Angle or Thickness views to an equivalent spline or Bezier curve with a specified number of points. The new curve is an approximation of the original curve, and the error in the approximation depends on the complexity of the original curve and the specified number of points for the new curve. This operation is very helpful for simplifying a curve with many points, either because it was imported or was interpolated. The context menu items are: 'Convert to Bezier' and 'Convert to Spline'. They are available in both the Angle and Thickness views. When choosing either of these options, you are asked to specify the number of points for the new curve in a dialog box. After clicking OK, you are required to select the curve segment to convert in the graph view. The curve will be converted immediately following your selection.

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ANSYS BladeEditor

Converting Angle Definition Data If you select the CamDef feature at the root tree level and change the Angle Definition Type, e.g. to Beta from Theta, then the input data in the graph will be kept as is, and will be taken as the data for the new angle type. If you switch from Theta to Beta, the Theta reference will be defaulted to zero. This switch will likely change the shape of the camberline. If you select the CamDef feature under a Blade feature and change the Angle Definition Type, then the angle data is converted to the new type. This conversion will try to retain the shape of the camberline by interpolation. Thirty points are used in the interpolated curve.

Forcing Interpolation of the Definition Data You may want to insert a CamDef feature into an existing blade without initially changing the shape of the blade. In this case an interpolation is required. You should multi-select the CamDef feature to be inserted along with the Blade feature, and right-click “Insert and interpolate Camberline”. This would insert the CamDef feature into the selected Blade and re-initialize the data from the angle and thickness definitions. Which angle data to be interpolated would be determined by the Angle Definition Type in the CamDef feature. The selected CamDef feature cannot be referenced by another blade.

Blade Feature The Blade feature is the geometry feature that is responsible for creating a blade or blade set. This feature defines the key properties of the blade, such as the blade type and the leading and trailing edge location and shape. It references the angle and thickness definitions to define the blade profiles. A given Blade feature (and its child Splitter features) must not overlap with other Blade features (and their child Splitter features) within a given FlowPath. The feature properties are as follows: Details of [Feature Name] Blade

[Feature Name]

Camberline Definitions

[CamDef selections]

Type

[Rotor | Stator]

Number of Blade Sets

[Int Value]

Surface Construction

[General | Ruled Element]

Blade Extension (%)

[Value]

Leading Edge Details Contour

[Sketch selection]

Type

[Ellipse | Cut-off | Square]a

Ratio at Hub (for Ellipse only)

[Value]

Ratio at Shroud (for Ellipse only)

[Value]

Trailing Edge Details 34

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Blade Feature Contour

[Sketch selection]

Type

[Ellipse | Cut-off | Square]

Ratio at Hub (for Ellipse only)

[Value]

Ratio at Shroud (for Ellipse only)

[Value]

Advanced Properties (Hidden by default) Number of Points Along the Blade

[Int Value]

Number of Points for LE (for Ellipse only)

[Int Value]

Number of Points for TE (for Ellipse only)

[Int Value]

Camberline/Thickness Definitions: [number] Camber/Thick Def. 1

[CamDef reference]

Camber/Thick Def. 2

[CamDef reference]

a Note that you cannot specify a perfectly sharp trailing edge. As a workaround, you can specify a square trailing edge with a small, but finite, thickness (for example, 0.05 mm).

The Type property specifies whether the blade is a rotating or stationary component. The FlowPath selection is the reference to the FlowPath feature, which is mandatory. The CamDef selections are the references to the CamDef features that describe the angle and thickness definitions; these are also mandatory. At least one CamDef with a specified angle definition must be selected to define the Blade. If only one angle definition is specified, the angle definition must be given on either the hub or the shroud. The same rule applies for the thickness. If the Surface Construction type is set to “Ruled Element”, then only two CamDefs may be selected, and they must be defined at the hub and shroud. Once the CamDefs have been selected, they will appear (for reference only) under the section at the bottom of the list "Camberline Definitions". In the tree view, CamDef features appear as sub-nodes of the Blade/Splitter feature. When the CamDef feature is highlighted from the sub-node position of Blade/Splitter feature, the angle curve and thickness curve can be displayed as percentage M/Mp values and actual Mp/M values based on current blade/splitter. When the curve in angle or thickness graph pane is modified, the CamDef feature is updated simultaneously. The display for blades/splitters referring to the CamDef feature may not be updated until the generation is finished. If you want to insert a CamDef feature into an existing Blade feature without initially affecting the shape of the blade, the ‘Insert/Interpolate Camberline’ operation can be used. Multi-select a new CamDef feature along with the Blade feature, right-click, and select ‘Insert/Interpolate Camberline’. The angle and thickness data of the selected CamDef feature will then be updated by interpolating from the blade definition.

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ANSYS BladeEditor

Splitter Feature This feature creates a new blade relative to an existing (main) blade such that the new blade (or splitter) shares the same Flow Path and blade count, and is generally assumed to be part of the same blade row. The base object of this feature is the selected Blade feature; only one Blade feature can be selected per Splitter feature. The Splitter feature can be one of two forms: a cloned splitter or an independent splitter. The form is specified in the feature properties. Once the feature has been created, you cannot change the type. The following topics will be discussed: Cloned Splitter Independent Splitter

Cloned Splitter A cloned splitter shares the same blade shape as the main blade, but is offset in theta from the main blade. Typically, a cloned splitter is trimmed by the BladeTrim feature to shorten the blade, e.g. the splitter in a centrifugal compressor. The feature properties are as follows: Details of [Feature Name] Splitter

[Feature Name]

Type

Cloned

Main Blade

[Blade feature selection]

Offset Type

[Pitch Fraction | Specified Angle]

Pitch Fraction

[Value: 0-1]

or Angle

[Value]

The Offset Type specifies how the splitter will be offset relative to the main blade. If “Specified Angle” is selected, then the angular offset of the cloned splitter blade relative to the main blade is specified directly. If “Pitch Fraction” is selected, then the pitch fraction as a value between 0 and 1 is specified. The pitch fraction represents the fraction of distance between two adjacent main blades. The actual angular offset is: offset = pitch fraction * 2 * pi / n where n is the number of main blades.

Independent Splitter An independent splitter can have a completely different shape than the main blade, but it still shares the same blade count and has a fixed offset from the main blade. The feature properties are nearly identical to the Blade feature except for the additional main blade reference and offset value. The properties are as follows: Details of [Feature Name]

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Splitter Feature Splitter

[Feature Name]

Type

Independent

Main Blade

[Blade feature selection]

Offset Type

[Pitch Fraction | Specified Angle]

Pitch Fraction

[Value: 0-1]

or Angle

[Value]

Offset Reference (Only for Pitch Fraction)

[Hub at Leading Edge | Hub at Trailing Edge]

Camberline Definitions

[CamDef selections]

Surface Construction

[General|Ruled Element]

... (the remaining details are the same as for the Blade feature) The interpretation of the Offset Type is different for an independent splitter than for the cloned splitter. If “Specified Angle” is selected, then the angular position of the splitter will be determined by the camber surface theta, shifted by the specified angle. If “Pitch Fraction” is selected, then you enter the pitch fraction as a value between 0 and 1, for the cloned splitter. However, because an independent splitter can have a different shape than the main blade, an Offset Reference must be specified. This determines how the splitter will be positioned relative to the main blade. The angular offset and the offset reference determine the reference theta for the splitter blade. When “Hub at Leading Edge” is selected for the Offset Reference, the reference theta and the camberline locations are calculated as follows: 1.

An offset reference meridional location is calculated at the intersection of the hub contour and the splitter leading edge contour.

2.

For the offset meridional location, the main blade theta value is calculated from the main blade cambersurface.

3.

The reference theta is then calculated by adding the angular offset (from the pitch fraction or specified angle) to the main blade theta value.

4.

All splitter camberline theta values are offset internally so that the splitter hub camberline starts at the reference theta.

Alternatively, when “Hub at Trailing Edge” is selected for the Offset Reference, the reference theta and the camberline locations are calculated as follows: 1.

An offset reference meridional location is calculated at the intersection of the hub contour and the splitter trailing edge contour.

2.

For the offset meridional location, the main blade theta value is calculated from the main blade cambersurface.

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ANSYS BladeEditor 3.

The reference theta is then calculated by adding the angular offset (from the pitch fraction or specified angle) to the main blade theta value.

4.

All splitter camberline theta values are offset internally so that the splitter hub camberline ends at the reference theta.

When a BladeGen model with splitters is imported, the theta values shown for the splitter camberlines may appear to differ in BladeEditor. The reason is that BladeGen always calculates the splitter reference theta using a meridional location at the main blade leading edge rather than at the splitter blade leading edge. When the splitter camberline definitions are imported they are converted to preserve the blade position and shape, and therefore the point data for the definitions may differ.

Stage Fluid Zone Feature The “fluid zone” represents the 3D fluid region within the flow passage, and is used to define the extent of the CFD domain. In release 11.0, a fluid zone was automatically created for each ImportBGD feature, which included the fluid region around a single blade row. For multiple blade rows, the fluid zone must include separate regions for, and have distinct interfaces between, each blade row. In release 12.0, a new StageFluidZone feature takes as a reference the selected FlowPath feature, and creates solid bodies for the fluid region in every blade row of the flow path. The first stage fluid zone in the flow path will start at the inlet contour and extend to the first interface (or to the outlet contour if there is only one blade row). The last stage fluid zone starts at the last interface and extends to the outlet contour. All intermediate stage fluid zones start and end at the interfaces adjacent to the blade row. The individual bodies are “frozen” so that they are not merged to adjacent solid bodies, including adjacent stage fluid zone bodies. (Individual bodies can be suppressed or hidden using existing DM functionality.) The StageFluidZone feature respects any BladeClearance, BladeTrim, or FlowCut features that have been applied to the FlowPath or blade rows prior to the StageFluidZone feature. All active bodies (blades, hub, etc.) are subtracted from the fluid zone. The stage fluid zone upstream and downstream interfaces are located by default halfway between the closest extents of the adjacent blade rows. For this to work, the StageFluidZone feature assumes that there is no overlap between adjacent blade rows; the StageFluidZone feature reports an error if this condition is violated. (Overlapping blade designs should be created using a combination of the Blade and Splitter features.) You may adjust the relative location of the interface by using one value in the range 0-1. The feature properties are as follows:

Table 1 Details View for StageFluidZone Feature Details of [Feature Name] StageFluidZone

[Feature Name]

Flow Path

[FlowPath feature selection]

Create Named Selections

[Yes | No]

Interface Detail 1: Interface Location

[Value: 0-1, default 0.5]a

Interface Detail 2: Interface Location

[Value: 0-1, default 0.5]a

a

0 corresponds to the aftmost trailing edge of the set of blades in the upstream blade row. 1 corresponds to the foremost leading edge of the set of blades in the downstream blade row.

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Throat Area Feature The Create Named Selections property determines whether the feature will automatically create named selections for each stage fluid zone. The Interface Details groups are created dynamically depending on the number of interfaces involved (number of blade rows less one.) Named selections are created automatically for each blade row of the StageFluidZone. The naming convention is Hub_[Main Blade Name], Shroud_[Main Blade Name], Blade_[Blade Name], etc. where Main Blade Name is the name of the main blade in the given blade row. For the Blade_ regions, each blade in the blade row will have a separate region defined. Named selections will not appear in DesignModeler, but they will appear if you load the .agdb file into the Mechanical application or the Meshing application, provided that you have set the properties of the Geometry cell (on the Project Schematic page in ANSYS Workbench) as follows: •

Attributes is selected.

•

Attribute Key string is cleared. (This setting appears when Attributes is selected.)

•

Named Selections is selected.

You can make the Geometry cell settings this way by default by selecting Tools > Options from the ANSYS Workbench main menu, browsing to the Geometry Import branch, and setting CAD Attributes (same as Attributes), CAD Attributes > Filtering Prefixes (same as Attribute Key), and Named Selections.

Note If the StageFluidZone periodic interfaces do not appear to be trimmed appropriately on the hub or shroud boundaries, you can try increasing the Blade Extension property for the corresponding blade feature to remedy the problem. The StageFluidZone feature uses this property to control how the periodic interfaces are created.

Throat Area Feature The throat area (ThroatArea) feature is used to calculate and display the throat surface(s) for one or more selected blade rows. The calculation is normally updated each time you issue the Generate command. The feature may be suppressed to avoid the calculation time when it is not needed, or the feature may be deleted if it is no longer needed. The feature properties are as follows:

Table 2 Details View for ThroatArea Feature Details of [Feature Name] ThroatArea

[Feature Name]

Blade

[Blade feature selection]

Location

[Leading Edge | Trailing Edge | Minimum Area]

Throat Surface Extension

[Value]

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ANSYS BladeEditor Throat Details: Area

[Value]

Layer 1 Length

[Value]

Layer 2 Length

[Value]

... ... ... Blade items are listed for all selected blades. The input property, Blade, is a Blade feature selection used to indicate the blade row. The Location property specifies the region for which to calculate the passage area. The choices are as follows: •

Leading Edge - computes the passage area in the region of the main blade leading edge.

•

Trailing Edge - computes the passage area in the region of the main blade trailing edge.

•

Minimum Area - computes the minimum passage area considering all blades in the blade row.

The Leading Edge option can report the throat width for a throat location that is a considerable distance away from the leading edge. A similar statement applies for the Trailing Edge option. The minimum area calculation uses a minimization algorithm based on the blade profiles on the design layers of the blade. If there are only one or two defining layers, then additional layers will be inserted for the purpose of the calculation. The output property group contains the throat area and the throat lengths for each layer defined in the flow path. The throat surface is displayed in the viewer as a frozen sheet body. The Throat Surface Extension property enables you to control the surface extension to ensure that the throat surface is cut by the blade bodies properly. This is an advanced property and it is shown only if the Show Advanced Properties preference is selected.

Note The minimization calculation of the throat surface area uses the raw blade profile data from the Blade feature and not the final solid model. The actual throat surface area is calculated from the solid model.

Note For Vista TF users: The throat widths are not added to the Vista TF geometry file. The throat data can be added manually. See the .geo file format description in Specification of the Geometry Data File (*.geo) (p. 83).

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Importing Blades from ANSYS BladeGen

Importing Blades from ANSYS BladeGen BladeEditor provides a geometry connection between BladeGen and DesignModeler. Reasons for importing BladeGen blades into DesignModeler include: •

ANSYS BladeGen can output geometry in many different point data formats, but its surface output in IGES format is cumbersome to use.

•

BladeGen does not produce a solid model in a standardized format such as Parasolid.

•

You can combine an imported blade with other CAD geometry imported via one of the many DesignModeler-supported CAD file formats.

Through BladeEditor, one or more BladeGen models can be linked into a DesignModeler session, so that any changes to the BladeGen models will be reflected in DesignModeler the next time you update the Geometry cell. When you import a BladeGen model, BladeEditor does the following: •

constructs blade surfaces

•

creates a solid model for the blades and hub

•

creates 2-D sketches for the meridional contours and non-flow-path hub geometry

•

creates periodic fluid zones

The preferred method of importing a BladeGen file is to create a link from the Blade Design cell of a BladeGen system to the Geometry cell. This link maintains the data transfer relationship between the two cells. The desired import options should be set in the Blade Design cell properties. (See Table 1: BladeGen Blade Design Cell Properties (p. 14) for more information.) After you make the link, the Geometry cell should be updated to process the imported geometry.

Note If you edit the Geometry cell before updating it, then the Import BGD feature details that are shown in BladeEditor may not accurately reflect the Blade Design cell properties. To refresh the Import BGD feature properties, click in BladeEditor. It is not recommended that you edit the Import BGD properties inside BladeEditor because they will be overwritten by the properties from the Blade Design cell the next time you update the Geometry cell.

Alternatively, you can import a BladeGen file from outside the project. To do this, click in the BladeEditor toolbar. When you click this icon, you will be prompted for the location and name of the BladeGen (.bgd) file. Once the filename is selected, the details view will let you select the properties for the import. These properties are listed in Table 3: Properties for the Import BGD File Feature (p. 42). As with

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ANSYS BladeEditor other DesignModeler feature properties, you can double-click in a property value box to change the selection to the next choice, or single-click on the property and select the value from the drop-down list.

Table 3 Properties for the Import BGD File Feature Property

Default Value

Function

ImportBGD

ImportBGD#

This property defines name of the import feature.

Source

(selected BGD File)

This property defines the name and path of the imported .bgd file. You can change the source to a new .bgd file if Refresh is set to Yes.

Unit Preference

(default is the DesignModeler length unit)

You may change the value of this property to the intended BladeGen model length unit if the latter does not match the DesignModeler length unit. If the BladeGen model length unit is specified as “Unknown” (in the BladeGen model properties), then BladeEditor will interpret the model as having the length unit specified here, and will process the model by converting from this unit into the DesignModeler length unit. Otherwise, the unit specified here will be ignored, and the model will be converted from the unit specified in the .bgd file into the DesignModeler length unit. It is recommended that you specify a length unit in BladeGen so that this information is stored in the .bgd file. Make sure that the length unit specified here is appropriate for the model. If the BladeGen dimensions are too small, DesignModeler may fail to import the BladeGen model.

Create Hub

Yes

If this property is set to Yes, then BladeEditor will create a HubProfile sketch for the non-flow path hub geometry, and will create a revolved body feature called HubBody.

Hub Offset

1 (Inch)

This property defines the default line offset (in the preferred length unit) for creating the initial HubProfile sketch. Note that this property is available only if Create Hub is set to Yes.

Create Blades

All

If this property is set to All, then BladeEditor will create all the blades using the number of blades specified in the BladeGen model. If this property is set to 1, then only the first blade will be created.

Merge Blade Topology

Yes

If this property is set to No, then BladeEditor will create the blade with four faces corresponding to the leading edge, pressure side, trailing edge and suction side. This can make it easier to create a structural mesh for the blades in the Mechanical application. If this property is set to Yes, then the blade faces will be merged where they are tangent to one another.

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Importing Blades from ANSYS BladeGen Property

Default Value

Function

Blade Loft Direction

Streamwise

If this property is set to Streamwise, then BladeEditor will loft the blade surfaces in the streamwise direction through curves that run from hub to shroud. This is the default because the surface is more well defined, especially for flank-milled blades. If this property is set to Spanwise, then BladeEditor will loft the blade surfaces in the spanwise direction through the blade profile curves.

Create Shroud Clearance

No

This property specifies whether a shroud clearance is created. If No is selected, then no shroud clearance is created. To create a shroud clearance, choose either Relative Layer or Absolute Layer. The blade(s) will be trimmed off at the selected BladeGen output layer, and the layer contour will be created in the LayerProfile sketch. If Relative Layer is selected, then the selected Layer Number is relative to the shroud layer, e.g., 1 implies the first layer closest to the shroud layer, 2 implies the second closest layer to the shroud, etc. If Absolute Layer is selected, then the selected layer index counts up from the hub layer, which is zero.

Layer Number

1

This property defines the selected layer index for the shroud clearance. Note that this property is available only if Create Shroud Clearance is selected.

Create Fluid Zone

Yes

If this property is set to Yes, then BladeEditor will create a StageFluidZone body for the flow passage, and an Enclosure feature to subtract the blade body. The resulting Enclosure can be used for a CFD analysis of the blade passage.

Create Named Selections

Yes

If this property is set to Yes, then BladeEditor will create NamedSelections (regions) for the typical faces of the blade passage, i.e., Blade, Hub, Shroud, Inflow, Outflow, PeriodicA and PeriodicB. These NamedSelections can be used as selection groups in other ANSYS Workbench applications, e.g., as regions in CFX-Mesh. Note that this property is available only if Create Fluid Zone is set to Yes.

Blade Extension (%)

2

This property defines the surface extension length (as a percentage of the average hub to shroud distance) for the blade surfaces. These surfaces are extended and then trimmed to the MasterProfile sketch to ensure that the blade solid correctly matches the hub and shroud contours.

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ANSYS BladeEditor Property

Default Value

Function

Periodic Surf Extension (%)

5

This property defines the surface extension length (as a percentage of the average hub to shroud distance) for the periodic surfaces. These surfaces are extended to ensure that the StageFluidZone is properly cut.

Periodic Surf Style

Three Pieces

This property specifies the style of the periodic interface surfaces. If Three Pieces is selected, then the periodic surface is created in three connected pieces: one upstream of the blade, one within the passage, and one downstream of the blade. This style can better accommodate highly curved or twisted blades, and is similar to the ANSYS TurboGrid style of periodic surface. If One Piece is selected, then the periodic surface is created as a single surface. Note that this property is available only if Create Fluid Zone is set to Yes.

Refresh

Yes

This property specifies whether the imported BladeGen model should remain linked to the DesignModeler session. If this property is set to Yes, then when the DesignModeler Generate button is clicked, BladeEditor will check to see if the BladeGen file has changed. If the BladeGen file has been modified, BladeEditor will reload the file. If the BladeGen file has moved or has been deleted, BladeEditor will switch this property to No and will leave the blade geometry unchanged. If this property is set to No, then BladeEditor will not reload the BladeGen file when the DesignModeler model is regenerated.

Once these properties have been set, click the Generate button, and the BladeGen model will be imported. The following features will then be created in the tree view: •

MerPlane: this plane is a copy of the Z-X plane; it is the plane on which the blade design sketches are created. –

MasterProfile: a sketch defining the hub, shroud, leading edge, trailing edge, inflow and outflow boundaries of the blade passage (imported from the .bgd file) will be created. This sketch is used during the creation of the blade bodies, and can be used to create the fluid zone. You should not modify this sketch.1

–

BladeProfile: a sketch defining the locations of the leading and trailing edges for the main blade will be created.

1

This constraint is to prevent the MasterProfile and the blades from becoming inconsistent, because the blade surface data comes from BladeGen.

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Using and Exporting Blades –

HubProfile: a sketch defining the hub body will be (optionally) created. This sketch can be modified; however, you should take care to ensure that the sketch loop remains intact or the hub body will fail to regenerate. HubBody - (Optionally) the HubProfile sketch is revolved to create the HubBody feature in the tree view.

•

BladeBody - The blade surface data is imported and lofted in DesignModeler to create the BladeBody feature in the tree view.

•

StageFluidZone - (Optionally) the MasterProfile sketch is revolved and cut into a sector by the periodic surface to form the StageFluidZone body. This feature forms a sector of the fluid volume around a single blade, but the blade has not been removed from the volume.

•

Enclosure - When the StageFluidZone is created, the blade (and any other connected geometry) is removed from the StageFluidZone body by the Enclosure feature.

•

Named Selections - These are the labeled regions on the final Enclosure body: Blade, Hub, Shroud, Inflow, Outflow, PeriodicA and PeriodicB.

Loading and Modifying Blades from ANSYS BladeGen If you create a blade from scratch in BladeEditor, or if you convert a BladeGen BGD file into BladeEditor features (by clicking ), then you can modify the blade by editing any of the features in the Tree Outline. If you have imported the blade from BladeEditor, the blade will be dependent on the BladeGen BGD file, but you can still modify the HubProfile sketch that appears under the associated MerPlane feature.

Note If you edit the hub sketch, make sure to maintain a closed edge loop when modifying this sketch or the hub body will fail to be generated. You can check the loop while editing the sketch by right-clicking in the viewer, choosing Select Loop/Chain and then selecting an edge of the loop. This will highlight the loop and let you inspect it in order to make sure that it is uniquely closed. You can modify the blade geometry using any of the standard DesignModeler geometry features. Some examples of the latter are: •

Adding edge blends to the blade geometry

•

Trimming the blade and/or hub bodies

•

Adding extrusions

Using and Exporting Blades Once the model is ready in DesignModeler, you can quickly analyze it in the Mechanical application. BladeEditor can also construct a solid model of the periodic flow passage that can be used to perform a CFD analysis of the flow path geometry. When needed, you can use DesignModeler to export the blade model to the Parasolid, IGES, or STEP file format to bring it into your native CAD system. You can also use BladeEditor to export the blade model for use in ANSYS TurboGrid or Vista TF.

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ANSYS BladeEditor The following topics are discussed: Export to Vista TF (.geo) Export as Meanline Data (.rtzt file) Export to ANSYS TurboGrid

Export to Vista TF (.geo) Similar to the ExportPoints feature, the VistaTFExport feature is used to define the parameters necessary to write the flow path geometry data (.geo file) for Vista TF. The .geo file contains a 2D mesh of the flow path geometry, including the locations of the blade leading and trailing edges. The .geo data also includes the blade type, blade camber surface data, blade thickness data and blade count for each blade row. If the ThroatArea feature (see Throat Area Feature (p. 39)) is used for a selected Blade, the throat information for that blade will be written to the .geo file. This information may improve the calculation of the choke mass flow rate in the Vista TF solver. Without this information, Vista TF will make its own estimate of the throat area. The feature properties are listed below.

Table 4 Details View for Meanline Export Details of [Feature Name] Export Points

[Feature Name]

Blade(s)

[Blade feature selection]

Export to file

[Yes | No]

(If Export to file = Yes)

[.geo filename]

Geo File Name Streamwise Mesh Count

[Integer Value > 2]

Spanwise Mesh Count

[Integer Value > 1]

Selected Blades: [number]a Blade 1

[Blade reference]

Blade 2

[Blade reference]

Blade 3

[Blade reference]

a

Blade items are listed for all selected blades.

Note The Vista TF solver expects the flow path (from inlet to outlet) to be oriented in the direction of the machine axis, which is the Z-axis. The VistaTFExport feature requires you to select the Blade features that will be exported to the .geo file. The selected blades must all belong to the same flow path. Therefore, the VistaTFExport feature can only export the data for a single flow path. Only the selected blades in the flow path will be considered for export; all other blades in the flow path will be ignored.

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Export as Meanline Data (.rtzt file) The ‘Export to file’ option specifies whether to explicitly save the data to a .geo file. When using the ANSYS Workbench project schematic, exporting to a file is unnecessary because the data is transferred automatically. If the .geo file is explicitly written, then you need to specify the .geo file name. The .geo file contains the geometry coordinates for the flow path in terms of quasi-orthogonal (q-o) ‘lines’ running from hub to shroud. The q-o lines are spaced approximately uniformly from inlet to outlet, based on the mid-span meridional length. The number of q-o lines is specified by the ‘Streamwise Mesh Count’ property, where the minimum count is determined based on the number of selected blades in the flow path. If the specified Streamwise Mesh Count is less than the calculated minimum, then the calculated minimum will be used. The number of q-o lines has a direct impact on the throughflow calculation accuracy and computation time. Increasing the number can improve accuracy, but it will also increase computation time. Increasing the number beyond a certain maximum may cause instabilities in the convergence process. Typical radial impellers with an axial inducer should be calculated with around 15 q-o lines in the bladed region, which equates to approximately a q-o line every 5° of curvature. The Spanwise Mesh Count property specifies the number of points used to define each quasi-orthogonal line; the points are uniformly spaced from hub to shroud. The minimum number is two. Increasing this parameter will improve the exported geometry representation for highly curved blades, but it should not be necessary to go beyond about 30. This parameter has no effect on the number of streamlines that are actually used in the throughflow calculation. When the .geo file is generated, a warning will be given for the VistaTFExport feature if the streamwise to spanwise aspect ratio of any of the mesh elements is greater than 15 or less than 1/15. Depending on the aspect ratio, you will be suggested to increase or decrease the appropriate streamwise or spanwise mesh count.

Export as Meanline Data (.rtzt file) To export meanline data, click the Add export points feature icon and set Export Type to Meanline. The meanline data gives the camberline/thickness definitions on each output layer in an rtzt format (r, theta, z, normal thickness.) Meanline data is exported based on the camber surface and thickness surface data represented internally. Therefore, this data may not be representative of the blade if solid model operations have been made to the blade geometry. An ExportPoints (Meanline) feature defines the point output for exactly one blade row. A multi-blade row model would require multiple ExportPoints features to output data for more than one blade row. All blades (the main blade and all existing splitter blades) in a single blade row are exported by a single ExportPoints feature. Regardless of whether you select a main blade or a splitter blade when defining the Blade parameter of an ExportPoints feature, the Blade parameter will always display the main blade. If you suppress any blade in a blade row, the ExportPoints feature for that blade row will also be suppressed. The feature properties are listed below:

Table 5 Details View for Meanline Export Details of [Feature Name] Export Points

[Feature Name]

Export Type

[Meanline | TurboGrid]

Blade

[Blade feature selection]

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ANSYS BladeEditor Point Distribution

[Uniform in M | Uniform in camberline length]

Number of Points

[Value>1]

Output Layers:

a

Output Layer 1?

[Yes | No]

Output Layer 2?

[Yes | No]

Output Layer 3?

[Yes | No]

a

Layer items are listed for all layers defined in the Flow Path.

For the Meanline export type, all blades in the selected blade row are exported. The ‘Number of Points’ property specifies how many points are exported from the leading edge to the trailing edge for each blade. The number of points upstream and downstream of the blade(s) is determined by the length tolerance and the shape of the flow path contours. The Blade selection lets you select the Blade feature of interest. However, all blades in a blade row are exported.

Export to ANSYS TurboGrid To transfer blade geometry data to the Turbo Mesh cell of a TurboGrid system, you need to link the Geometry cell to the Turbo Mesh cell and create an ExportPoints feature in BladeEditor to specify which blade geometry should be exported. The ANSYS TurboGrid export type provides the blade profile data in a format suitable for defining the blade geometry in ANSYS TurboGrid. To create the ExportPoints feature, click the icon and set Export Type to TurboGrid. You must then select the Blade feature or FlowPath feature and select the surfaces of the blade from which to extract the blade profile data. The blade profile (point) data is automatically extracted from the blade solid model at the specified output layers.

Note Care must be taken to ensure that sufficient output layers are used when exporting so that the ANSYS TurboGrid blade surface is a reasonable approximation of the BladeEditor solid model. Note that using many output layers with a small point tolerance can cause Bspline surface lofting problems in ANSYS TurboGrid. In these cases, you may need to override the Blade Geometric Representation in ANSYS TurboGrid and change the Curve and Surface Types to 'Piece-wise linear' and 'Ruled', respectively. You will need to use one ExportPoints feature for each blade that you wish to export, even if they are in the same blade row. For example, if you have a main blade and a splitter, you will need to create two ExportPoints features and select the appropriate blade surfaces for each feature. You specify which exported blade(s) to load into ANSYS TurboGrid by editing the Turbo Mesh cell properties. See Table 1: TurboGrid Turbo Mesh Cell Properties (p. 53) for more information. Because the blade profile data is extracted from the blade surfaces, this feature can also be used to extract blade profile data from an imported CAD model. The only requirement is that a FlowPath feature must be defined to specify the output layers. If you specify a FlowPath as the Base Feature property, you will need to specify the number of blades and the blade row number. The blade row number lets TurboGrid know

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Export to ANSYS TurboGrid how the exported blades are ordered, and whether any exported blades are part of the same blade row. The blade rows are sorted in ascending order from inlet to outlet. The blade profile data can also be exported to a file for use by an external application by setting the 'Export to file' property to 'Yes'. The feature properties are listed below:

Table 6 Details View for Export to ANSYS TurboGrid Details of [Feature Name] Export Points

[Feature Name]

Export Type

[Meanline | TurboGrid]

Export to file

[Yes | No]

(If Export to file = Yes)

[Folder name]

File Folder (If Export to file = Yes)

[Filename prefix]

File Prefix Base Feature

[FlowPath or Blade feature selection]

Flow Path

[FlowPath feature selection]

Blade Surfaces

[Named Selection for blade surfaces]

Blade Info from

[Blade feature | User Specified]

(if User Specified)

[Value>1]

Number of Blades (if User Specified)

[Int Value]

Blade Row Number Hub/Shroud Offset [0
[Value>1] a

Output Layer 1?

[Yes | No]

Output Layer 2?

[Yes | No]

Output Layer 3?

[Yes | No]

a

Layer items are listed for all layers defined in the Flow Path.

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ANSYS BladeEditor

Configuring the BladeModeler License BladeModeler requires an ANSYS license to use, although BladeGen will run in "demonstration" mode without the license (no saving or exporting is possible in this mode). Without the license the BladeGen system does not appear in the Toolbox, and the only way to access BladeGen is to open a previously saved project that contains a BladeGen system. Please contact your ANSYS representative to obtain a license for BladeModeler if you do not already have one. One BladeModeler license will permit a single user to have BladeGen, DesignModeler, and BladeEditor running together in the same ANSYS Workbench session. This license sharing ability means that no additional DesignModeler license will be required to use the full functionality of BladeModeler. In order to use BladeEditor, you must set the Geometry license preference to ANSYS BladeModeler as follows: 1.

In the ANSYS Workbench menu, select Tools > License Preferences.

2.

In the License Preferences dialog box, click the Geometry tab.

3.

If ANSYS BladeModeler is not the first license listed, then select it and click Move up as required to move it to the top of the list. Furthermore, you should select ANSYS DesignModeler in the list and set its value to 0 (which means “Don't Use”). This prevents DesignModeler from using an ANSYS DesignModeler license when an ANSYS BladeModeler license is not available. If ANSYS BladeModeler is not in the list then you need to obtain an ANSYS BladeModeler license.

4.

Click OK to close the dialog box.

Click the Help button in the License Preferences dialog box for more information.

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Configuring the BladeModeler License

Note IMPORTANT WARNING FOR USERS THAT HAVE AN ANSYS DESIGNMODELER LICENSE A BladeEditor model will be destroyed if it is modified by DesignModeler under the ANSYS DesignModeler license. If your project involves a BladeEditor model, then you must ensure that DesignModeler operates under the ANSYS BladeModeler license (in which case DesignModeler is considered to be running as BladeEditor). Instructions for setting the license preferences appropriately are given above. With DesignModeler running under the ANSYS DesignModeler license, it is very important that you do not trigger the processing of any Geometry cell that represents a BladeEditor model; in this case, processing the Geometry cell would cause the associated geometry file to be overwritten with a corrupt version. Such processing can occur by updating all or part of the project, or by editing the Geometry cell then making changes in DesignModeler then closing DesignModeler. If you do edit a Geometry cell that contains a BladeEditor model, and you are using DesignModeler under the ANSYS DesignModeler license, then DesignModeler will display question marks beside some of the features listed in the tree view; these are the features that are not recognized by DesignModeler because they are intended for BladeEditor. In this case avoid saving from DesignModeler, then: 1.

Either exit ANSYS Workbench or click File > New to start a new project.

2.

Do not save the project when you are presented with a dialog box.

3.

Configure your license preferences as specified above.

4.

Reopen the project. The old (uncorrupted) files will be restored.

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ANSYS TurboGrid ANSYS TurboGrid is a meshing tool that is specialized for CFD analyses of turbomachinery bladerows. The ANSYS TurboGrid documentation is available from the Help menu in ANSYS TurboGrid. The main documentation is available from the Help menu in ANSYS TurboGrid, and consists of the following parts: •

ANSYS TurboGrid Introduction

•

ANSYS TurboGrid Tutorials

•

ANSYS TurboGrid User's Guide

•

ANSYS TurboGrid Reference Guide

To launch ANSYS TurboGrid from ANSYS Workbench, add the TurboGrid component system to your project schematic, then edit the Turbo Mesh cell of that system. The geometry can be loaded from the File menu in ANSYS TurboGrid, or it can be specified by linking a Geometry or Blade Design cell upstream of the Turbo Mesh cell. In the case when data is transferred to a Turbo Mesh cell from a Geometry cell, the Turbo Mesh cell has properties that control this transfer. These are described in Table 1: TurboGrid Turbo Mesh Cell Properties (p. 53). Before attempting to modify these properties, be sure to refresh the Turbo Mesh cell if it is in a Refresh Required state. Refreshing this cell causes the properties to be updated.

Table 1 TurboGrid Turbo Mesh Cell Properties Group

Name

Description

Geometry Selection

Flowpath Options

This property displays a list of the available flow paths and bladerows. Use this information as a guide when specifying the Flowpath and Bladerow properties (described below). Use the Refresh command in the context menu to update the list after linking.

Flowpath

This property specifies which Flowpath feature in BladeEditor contains the bladerow that is to be loaded in ANSYS TurboGrid.

Bladerow Number

This property specifies which bladerow (within the specified Flowpath feature) is to be loaded in ANSYS TurboGrid.

Inlet Position Method

This property specifies how the inlet points are positioned in TurboGrid. The Manual option means the user will specify these in TurboGrid. The Adjacent

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ANSYS TurboGrid Group

Name

Description Blade option means the inlet points will be calculated using the upstream bladerow, specified below. Only available when multiple bladerows have been specified in BladeEditor.

Upstream Bladerow Number

This property specifies the bladerow number for the bladerow that is immediately upstream of the current bladerow. This property is available only when Inlet Position Method is set to Adjacent Blade.

Outlet Position Method

This property specifies how the outlet points are positioned in TurboGrid. The Manual option means the user will specify these in TurboGrid. The Adjacent Blade option means the outlet points will be calculated using the downstream bladerow, specified below. Only available when multiple bladerows have been specified in BladeEditor.

Downstream Bladerow Number

This property specifies the bladerow number for the bladerow that is immediately downstream of the current bladerow. This property is available only when the Outlet Position Method is set to Adjacent Blade.

Each ExportPoints feature in BladeEditor defines a single blade, is associated with a FlowPath, and has a Bladerow Number. To model a series of consecutive bladerows in a turbomachine, you should define a series of ExportPoints features associated with the same FlowPath feature, with Bladerow Numbers in numerical order (lowest number at the inlet end of the machine). By using the same FlowPath number: •

You have access to the Turbo Mesh cell properties that collectively control the position of the inlet and outlet ends of each bladerow: Inlet Position Method, Upstream Bladerow Number, Outlet Position Method, Downstream Bladerow Number.

•

The machine is eligible to be analyzed by Vista TF. For help on Vista TF, see Vista TF User's Guide (p. 61).

If you want a given bladerow to contain more than one blade geometry (for example, main blades with splitter blades), create one ExportPoints feature for each unique blade in the bladerow, with each ExportPoints feature based on the same FlowPath and given the same Bladerow Number. When more than one ExportPoints feature matches the FlowPath and Bladerow Number criteria set in the Turbo Mesh cell properties, ANSYS TurboGrid will create a bladerow with splitter blades. You can access a context menu for the Turbo Mesh cell in the TurboGrid component system by right-clicking the cell. Most of the commands that are available are standard, and are described in Systems and Cells. The

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ANSYS TurboGrid only context menu command that is specific to the Turbo Mesh cell is the Edit command, which opens ANSYS TurboGrid.

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ANSYS CFX-Pre ANSYS CFX-Pre is a general-purpose CFD preprocessor that has a turbomachinery setup wizard for facilitating the setup of turbomachinery CFD simulations. The ANSYS CFX-Pre documentation is available from the Help menu in CFX-Pre. The documentation is named “ANSYS CFX-Pre User's Guide”.

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ANSYS CFD-Post ANSYS CFD-Post is a general-purpose CFD postprocessor that has features for facilitating the post-processing of turbomachinery CFD simulations. The ANSYS CFD-Post documentation is available from the Help menu in CFD-Post. The documentation is named “ANSYS CFD-Post User's Guide”.

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Vista TF The Vista TF program is a streamline curvature throughflow program for the analysis of any type of turbomachine, but has been developed in the first instance primarily as a tool for radial turbomachinery analysis. The program enables you to rapidly evaluate radial blade rows (pumps, compressors and turbines) at the early stages of the design. Vista TF is provided by PCA Engineers Limited, Lincoln, England. The documentation for Vista TF is provided in the following sections: Vista TF User's Guide Vista TF Reference Guide

Vista TF User's Guide The Vista TF program is a streamline curvature throughflow program for the analysis of any type of turbomachine, but has been developed in the first instance primarily as a tool for radial turbomachinery analysis. The program enables you to rapidly evaluate radial blade rows (pumps, compressors and turbines) at the early stages of the design. Vista TF is operated from ANSYS Workbench by working with the Vista TF component system. The latter is comprised of three cells: a Setup cell, a Solution cell, and a Results cell:

The name of the Vista TF system is changeable upon first adding the system, or by right-clicking the blue cell and selecting Rename, then typing in a new name. Note that the name of the system appears below the system. Vista TF uses the following input to define a run: •

A geometry (*.geo) file

•

Setup cell properties

•

Three Vista TF template files –

a control data file (*.cont)

–

an aerodynamic data file (*.aert)

–

a correlations data file (*.cort)

The general procedure for running a simulation in Vista TF is: Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF 1.

Drag the Vista TF component system from the Toolbox to the Project Schematic, or double-click the system in the Toolbox.

2.

Specify a geometry file using either one of the following methods: •

Connect an upstream Geometry cell that contains a VistaTFExport feature to the Setup cell. If there is more than one VistaTFExport feature, then the first valid and unsuppressed one is used.

• 3.

Right-click the Setup cell, select Import Geometry, and browse to select a geometry (*.geo) file.

Double-click the Setup cell, then configure the Setup cell properties. For details, see Vista TF Setup Cell Properties (p. 62).

4.

Optionally customize one or more of the three template files (*.cont, *.aert, *.cort). For details on customizing the template files, see Customizing the Vista TF Template Files (p. 66).

5.

Update the Solution cell, or update the Project, to generate a solution.

6.

Double-click the Solution cell to view the solver output.

7.

Double-click the Results cell to view the results in CFD-Post. The Results cell has one property that you can edit to control report generation.

The following topics are discussed: Vista TF Setup Cell Properties Customizing the Vista TF Template Files Vista TF Context Menu Commands

Vista TF Setup Cell Properties The main properties that control Vista TF are associated with the Setup cell. To see the properties, do any one of the following: •

Right-click the Setup cell and select Edit.

•

Double-click the Setup cell.

•

Right-click the Setup cell and select Properties.

A sample of the cell properties is shown in Figure : Properties of the Vista TF Setup Cell (p. 63).

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Vista TF Setup Cell Properties

Figure: Properties of the Vista TF Setup Cell

Table 1: Vista TF Setup Cell Properties (p. 63) describes each of the cell properties.

Table 1 Vista TF Setup Cell Properties Group

Name

Description

General

Cell ID

The name of the cell with which the present set of properties is associated.

Machine Type

This property appears when there is no cell upstream of the Setup cell. This property defines the machine type. The choices are: •

Pump

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Vista TF Group

Name

Description •

Axial Compressor

•

Centrifugal Compressor

•

Fan

•

Axial Turbine

•

Radial Turbine

•

Hydraulic Turbine

•

Other

•

Unknown

This property specifies which template files are used and which report is used for the results. You can customize these templates. For details, see Customizing the Vista TF Template Files (p. 66). Number of Blade Rows

This property appears when there is no cell upstream of the Setup cell. This property defines the number of blade rows in the geometry (.geo) file.

Solver Settings

Operating Conditions

Number of Streamlines

This property defines the number of meridional streamlines to use in the calculation. For details, see Specification of the Control Data File (*.con) (p. 74).

Maximum Iterations

This property defines the maximum number of solver iterations. For details, see Specification of the Control Data File (*.con) (p. 74).

Machine Rotational Direction

This property defines the direction of rotation of the blades about the Z axis. The choices are: •

Right-handed

•

Left-handed

Machine Rotational Speed

This property defines the rotational speed of the machine.

Flow Option

This property specifies the types of boundary conditions. The choices are:

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•

Mass Flow

•

Pressure Ratio

•

Pressure Difference

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Vista TF Setup Cell Properties Group

Name

Description For details, see Specification of the Control Data File (*.con) (p. 74) and Specification of Aerodynamic Data File (*.aer) (p. 91).

Pressure Ratio (For Flow Option = Pressure Ratio) Pressure Difference (For Flow Option = Pressure Difference)

Reference Values

Fluid Properties

This property defines the outlet-to-inlet ratio of absolute total pressures (each pressure measured in the stationary frame). This property defines the outlet-to-inlet difference of total pressures (each pressure measured in the stationary frame).

Mass Flow Rate

This property defines the inlet mass flow rate.

Inlet Total Pressure

This property defines the inlet absolute total pressure (measured in the stationary frame).

Inlet Total Temperature

This property defines the inlet absolute total temperature (measured in the stationary frame).

Inlet Swirl Angle

This property defines the angle of the inlet velocity measured with respect to the meridional plane. A positive angle implies that the flow swirls in the Machine Rotational Direction.

Reference Diameter

This property defines the reference diameter for all blade rows. For details, see Specification of Aerodynamic Data File (*.aer) (p. 91).

Polytropic Efficiency

This property defines the small-scale polytropic efficiency for the machine.

Fluid Option

This property defines the type of fluid that flows through the machine. The choices for this property are:

Gas Specific Heat Cp (For Fluid Option = Ideal Gas)

•

Ideal Gas

•

Liquid

This property defines the specific heat capacity (at constant pressure) of the ideal gas.

Specific Heat Ratio This property defines the specific heat ratio of the ideal gas. Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF Group

Name

Description

(For Fluid Option = Ideal Gas) Fluid Density (For Fluid Option = Liquid) Fluid Specific Heat (For Fluid Option = Liquid) Dynamic Viscosity

Initial Conditions

Initial Cm/U_ref

This property defines the density of the liquid.

This property defines the specific heat capacity of the liquid.

This property indicates the dynamic viscosity of the fluid as follows: •

A value less than 1 [N s m^-2] (or equivalent value in other units) is interpreted as the dynamic viscosity. Note that the value must be greater than 0.0000001 [N s m^-2].

•

A value of 0 causes Vista TF to calculate the dynamic viscosity from an inbuilt equation for dynamic viscosity based on Sutherland’s law and the Inlet Total Temperature. This works only for an ideal gas.

•

A value greater than 1 [N s m^-2] (or equivalent value in other units) is interpreted as the Reynolds number, in which case Vista TF calculates the dynamic viscosity using this Reynolds number, the Reference Diameter, the Machine Rotational Speed, and the fluid density.

This property serves as an initial guess for the meridional velocity divided by a characteristic velocity, where the latter is half the Reference Diameter multiplied by the Machine Rotational Speed. For more information, see the description for cm_start in Specification of the Control Data File (*.con) (p. 74).

Customizing the Vista TF Template Files When you run Vista TF, one of each of the *.cont, *.aert, and *.cort data files are copied from the Vista TF template directory into your working directory as required (that is, if they are not already present in the working directory). The exact *.cont, *.aert, and *.cort files that are copied (and then used during a run) depend on the Machine Type setting in the Setup cell properties. You can use custom versions of any of the *.cont, *.aert, and *.cort files. To customize one of these files:

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Vista TF Context Menu Commands 1.

Import the template you want to customize by right-clicking the Setup cell and selecting one of the Import Template commands. The selected template file is copied to the working directory. If you import the same template file more than once, the name of the copied file is changed automatically to produce a unique file name; the last one imported will take effect when you start a run.

2.

From the Workbench main menu, select View > Files to see the template files you have imported.

3.

Right-click the template file that you want to customize, and select Open Containing Folder.

4.

Open the template file in a text editor and change it. In these files, do not change setting values that are between a pair of braces (“{” and “}”). You can change setting values which are not wrapped in braces. The settings of the template files correspond with the settings of the *.con, *.aer, and *.cor files which are described in Specification of the Control Data File (*.con) (p. 74), Specification of Aerodynamic Data File (*.aer) (p. 91), and Specification of Correlations Data File (*.cor) (p. 101).

Vista TF Context Menu Commands You can access a context menu for each cell in the Vista TF component system by right-clicking a cell in the system. Most of the commands that are available are standard, and are described in Systems and Cells. The context menu commands that are specific to the Vista TF system cells are described in Table 2: Context Menu Commands Specific to the Vista TF System Cells (p. 67).

Table 2 Context Menu Commands Specific to the Vista TF System Cells Cell

Command

Description

Setup

Edit

This command opens the Vista TF properties view.

Import Geometry

This command enables you to specify the geometry file, provided that there is no upstream Geometry cell linked to the Setup cell.

Import Template

This command enables you to import a template file. For details, see Customizing the Vista TF Template Files (p. 66).

View Solver Output

This command opens the Vista TF screen output (.scn file) for viewing. For details, see Screen Output Files (screen.scn) (p. 74).

Continue Calculation

This command restarts the solver. You can use this command to continue a run that did not converge; in this case, the Update command may not work because the cell is already up-to-date.

Solution

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Vista TF Cell

Command

Description

Results

Edit

This command opens the results in CFD-Post.

Vista TF Reference Guide The Vista TF program is a streamline curvature throughflow program for the analysis of any type of turbomachine, but has been developed in the first instance primarily as a tool for radial turbomachinery analysis. The program enables you to rapidly evaluate radial blade rows (pumps, compressors and turbines) at the early stages of the design. The key aspect of this document is the input and output data specification for the program and how to run it. The input files include a control file, an aerodynamics file, a geometry file, a correlations file, and can also include a restart file providing data from a previous converged simulation. The input files include comment lines to help the reader to identify the parameters. The output files include a results file with text output for analysis of the simulation giving: •

Data on streamlines and quasi-othogonals (short for “quasi-orthogonal calculating stations”)

•

Various files with the same information that can be used for plotting the results

•

A file which monitors the history of the simulation

•

A file to act as interface to other software systems

•

A restart file which can be used to initialise a further simulation.

For radial pump and turbomachinery calculations in subsonic flow the program is very robust, but some tips on possible problems with running the program are also provided. The topics in this guide are: Running Vista TF from the Command Line Input and Output Data Files for Vista TF Software Limitations Streamline Curvature Throughflow Theory Appendices

Running Vista TF from the Command Line You can run Vista TF from the command line of your operating system. By default, the executable will look in the current directory for the required input files for your case. One of the input files, which has a default name of vista_tf.fil, contains the names of the other input files that are to be used for the case. If this input file has a different name, specify that name as the first command line argument. For example: VistaTF.exe myfile.fil When the executable runs, it writes text output messages to the console. To redirect these messages to a file, append -silent to the command line. The default file name for storing the redirected output messages is screen.scn. To store the output messages in a file of a different name, specify that name following -silent.

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Input and Output Data Files for Vista TF After running the program, several files are produced in .csv format as the basis for producing plots with CFD-Post or in .txt format as the basis for producing plots with Tecplot. The input and output files for VistaTF.exe are described in detail in Input and Output Data Files for Vista TF (p. 69).

Input and Output Data Files for Vista TF The following sections describe the input and output files for VistaTF.exe. The Auxiliary File with the Default Name: vista_tf.fil Overview of Input Files Overview of Output Files Specification of the Control Data File (*.con) Specification of the Geometry Data File (*.geo) Specification of Aerodynamic Data File (*.aer) Specification of Correlations Data File (*.cor) Specification of the Output Data File (*.out) Specification of the Text Data Files (*.txt) Specification of the CFD-Post Output Files (*.csv) Specification of Convergence History Data File (*.hst)

The Auxiliary File with the Default Name: vista_tf.fil You specify the input data and output data file names in an auxiliary data file which has the default filename vista_tf.fil. This file can have another name if this name is passed to the program through a commandline argument to specify the auxiliary filename, as described in Running Vista TF from the Command Line (p. 68). If no command-line argument is specified in this way, then the program assumes that the file has the name vista_tf.fil. This auxiliary file in turn must contain the necessary filenames for the input and output files in the following order and form: control datafile name geometry datafile name aerodynamic datafile name correlation datafile name results output file name convergence history filename text data output file name Cfx-post output file name restart datafile name Interface output file

prefix.con prefix.geo prefix.aer prefix.cor prefix.out prefix.hst prefix.txt prefix.csv prefix.rst prefix.int

Note that the prefixes need not be identical for a given run. In fact this is not usually the case. An example of a vista_tf.fil file is: standard_control.con impeller_XYZa.geo design_point.aer radial_impeller.cor results.out history.hst impeller.txt cfx_post.csv restart.rst stream.int

Note that the program also produces and uses other files in special situations as outlined below; their names do not need to be specified separately because they are determined by the program. The data files, results files, and the file vista_tf.fil should be in the same directory. If the history (.hst) file already exists Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF in the working directory before the program is run, it will be overwritten. If the restart (.rst) file already exists in the working directory before the program is run, it will be overwritten only if the solution has converged or reached the maximum number of iterations that you have specified. If the output (.out) file and the plot files (.txt, and .csv) already exist in the working directory before the program is run, they will be overwritten. The program will not prompt you for permission to overwrite these files.

Overview of Input Files Four input data files are always needed: Control data file (.con) Geometrical data file (.geo) Aerodynamic data file (.aer) Correlations data file (.cor)

A fifth input file will be used if it is available and if you specify that it should be used: Restart data file (.rst)

The division of the input data into separate files provides a simple and clear way to vary or retain the annulus geometry, the aerodynamic conditions, the blade element data, or the correlations being used, without changing all the files in use. Typically during the design process, you will change the .geo file to examine a new geometry, and the .aer file to examine new operating points or boundary conditions, and you will leave the .con and .cor files untouched once you have configured their settings to meet the requirements. The data specified in the individual files is structured to be as logical as possible, but some small overlap between the different files is inevitably necessary. The structure may appear more complicated than necessary, but this arises from the requirement that ultimately the program should calculate all types of turbomachinery in single stage and multistage configurations, both as ductflow and as throughflow calculations. During the development an attempt has been made to include a built-in “expert system” in the program. For example, the program itself is able to identify whether a particular blade row is a radial compressor impeller or a radial turbine inlet guide vane (from the geometry) and ultimately will be able to select automatically the most appropriate correlations to be used. In general many parameters may be set to zero and the program selects the value it deems appropriate. “Expert parameters” allow you to override the selections that the program would automatically make. The functions of the five input data files are summarized next:

Control Data File (.con) This is a short file giving values of identifiers of the file (title and headers) and control information and constants defining such choices as the number of streamline calculating planes, the convergence tolerance, the relaxation factors, and so on. Various “expert” parameters are also specified in this file. Also specified in this file are the planes and stations for which output information is required, and the level of detail requested on these planes. To make the program easier to use, you can specify many of these parameters as 0.0, 1.0, or 0, and the program will then make a sensible choice of the value for the parameter concerned, so that typically you are only concerned with two or three parameters in this file. The control parameters that determine the selection of particular numerical models are also defined in this file, for example the type of span-wise mixing or the model for blade row choking. In general, this input file does not need to be changed from run to run.

Geometry Data File (.geo) The geometry data file contains the dimensions of the annulus in terms of the axial and radial coordinates of the quasi-orthogonal calculating planes at hub and casing, and information to identify the type of calcu70

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Restart Data File (.rst) lating station (such as duct, stator, or rotor). Calculating planes can represent regions of a duct or blades (leading edges, trailing edges, and internal stations) and can be curved or linear. For linear calculating planes (which, by definition, are straight in the meridional plane), details of the geometry of each calculating plane are specified at only two points and intermediate geometric values are interpolated linearly from these, whereas curved planes require more points to be specified across the span. For curved duct calculating planes, this geometry data specifies the co-ordinate points along the curved calculating plane. In blade regions, the coordinates of the calculating plane, together with information about the blade geometry at this location, must be specified (including the number of blades, blade lean angles, and blade thickness). For each blade row, additional geometrical parameters can be specified that might be relevant for the correlations (such as the throat area, the location of the throat, the location of maximum camber, the maximum thickness, the trailing edge thickness, and the tip clearance). In general, the geometry data file will be generated automatically using a blade geometry definition program (such as ANSYS BladeEditor, or Vista GEO of PCA). A geometry conversion program is available to convert data from the BladeGen meanline RTZT output format into the .geo file format for the throughflow program and this has been tested for radial impeller rotors and stators, and axial stator and rotor blade rows (compressors and turbines); see Appendix G: The RTZTtoGEO Program (p. 147). Other custom tools are available for conversion of geometrical data from specific formats into the Vista TF .geo file format, and others can be prepared as required.

Aerodynamic Data File (.aer) The aerodynamic data file contains the definition of the fluid, boundary conditions, and operating data such as inlet conditions and rotational speed. It includes parameters related to aerodynamic models for the mean stream surface description, and the spanwise mixing coefficient.

Correlation Data File (.cor) The correlation data file provides details of control parameters and empirical constants and data for the particular choice of empiricism that has been chosen. The method allows a general specification of losses, flow angle, and blockage for all calculating planes and across the span through the definition of the spanwise variation of these parameters at particular quasi-orthogonal locations and for particular blade rows. Ultimately, in many cases, if default values of zero are chosen for these parameters then the program should automatically select appropriate correlations and make its own choice of correlation parameters.

Restart Data File (.rst) This restart file contains some key information from a previous calculation in a non-dimensional form. Note that the restart file can be for different flow conditions and for a different geometry but it must have the same number of quasi-orthogonal calculating stations and streamlines as the current calculation. If the restart data file has been generated from a calculation with similar geometry and flow conditions as the current calculation, it provides a much better initial estimate of the flow and the streamline positions than the first estimate generated internally within the program, promoting more rapid convergence. A restart with unchanged conditions and geometry will generally have a meridional velocity error of less than 2% and will converge almost immediately, except for choked flows where more iterations are needed. Convergence with the restart file is never immediate, even with unchanged geometry and flow conditions, because not all of the solution is saved to the restart file, and so some data needs to be regenerated over a few iterations of the solution. For small changes in flow conditions or geometry, the number of iterations when using the restart file is generally less than 50% of that required when starting from the program's own first estimate. An existing restart file cannot be used if the number of streamlines or quasi-orthogonals is changed. The program recognizes if the number of streamlines or quasi-orthogonals has been changed and makes a new cold start in this case. Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF You do not have to be concerned with the content and format of the restart file because it is generated automatically at the end of a run of the program, and is automatically used if it is available. No further information is provided here with regards to the content of the restart file. In some situations where it is difficult to obtain convergence, the restart file can be used to store results for a converged operating point (at lower speed, for example) and then the required operating condition can be obtained by starting from the restart file with new flow conditions. In other cases where an un-converged solution has been stored in the restart file, it is possible that using the restart file can be disadvantageous as a starting point for a new simulation, and a cold-start may be better. The restart file can also be used for reducing the number of computations when the program is coupled to an optimizer. In this case, an additional restart file with the name best_restart.rst is used and generated.

Overview of Output Files The program always creates the following three output files: •

Results output file (.out)

•

Convergence history file (.hst)

•

Restart data file (.rst)

In addition, the program can create the following output files of tabular data for plot and display purposes, depending on the value of the parameter i_display in the control file: •

Several comma separated variable output files for CFD-Post (.csv)

•

Several text output files in a format suitable for Tecplot (.txt)

There is one CFD-Post output file for a calculation with no blade rows and four additional files for each blade row. There are two Tecplot output files for a calculation with no blade rows, and an additional file for each blade row. In addition, the program can create a data file containing data in a specific format for use with other programs: •

Interface output file (.int)

and a file which can be produced as an alternative to the screen output: •

Screen output file (screen.txt)

Results Output File (.out) This contains rudimentary details of the data used for the calculation and the results of the calculation at every plane and radial station for which output has been requested. An overview of the content of this file is given in Specification of the Output Data File (*.out) (p. 111).

Convergence History File (.hst) This contains a recording of the input data, followed by details of the convergence of the main iterative procedures, and extensive details of the terms in the radial equilibrium equation for each stream tube and calculating plane. It is rare for this to be examined in any depth, but this can be useful to identify problems if the solution fails to converge.

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Text Data Output Files for Tecplot (.txt)

Restart Data File (.rst) This restart file stores information from a converged calculation in a non-dimensional form. It provides a much better initial estimate of the flow and the streamline positions than the first estimate generated internally within the program. It reduces the calculation time for a calculation with slightly modified geometry or changed aerodynamic data by more than 25%. If an existing restart file is available, it will be overwritten by the program.

Comma Separated Variable Output Files for CFD-Post (.csv) Depending on the value of i_display in the control file, the following files are produced: •

prefix.csv

•

global_prefix.csv

together with four additional files produced for each blade row from 1 to n: •

row_0n_hub_prefix.csv

•

row_0n_mean_prefix.csv

•

row_0n_tip_prefix.csv

•

row_0n_loading_prefix.csv

The first file (prefix.csv) contains key results of the calculation at every calculating plane and streamline in a form that can be used for setting up a meridional contour plot of the results. The second contains a summary of the global performance and reference parameters for the calculation. The additional four .csv files are produced for each blade row in the calculation. These contain the same information as in the row data from the .txt files, but separated into hub, mean, and tip streamline data, which is information along the blade calculating station from leading to trailing edge on the hub, mean, and tip streamlines. The additional file contains spanwise variation of data. This can be used to define typical blade loading diagrams and incidence plots for each blade row. Even if no .csv file is required, the prefix.csv file still needs to be specified in the vista_tf.fil file.

Text Data Output Files for Tecplot (.txt) Depending on the value of I_display in the control file, the following files are produced: •

prefix.txt

•

test_prefix.txt

Together with one additional file produced for each blade row from 1 to n: •

row_0n_prefix.txt

The first file (prefix.txt) contains key results of the calculation at every calculating plane and streamline in a form that can be used for setting up a meridional contour plot of the results, using Tecplot software. This is an ASCII file which is formally correct for presenting the results in graphical form with the plot processing software Tecplot, but can be used by other plot systems (such as Excel) with appropriate conversion or macros. A standard layout file for Tecplot (flowfield_2d.lay) has been prepared for typical meridional plots from Vista TF calculations. There are no macros included in this so this may need some adjustment for a typical case (scale of axes, level of contour values, and so on). The second text file (test_prefix.txt)

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Vista TF contains the grid of the initial estimate of the streamlines and quasi-orthognals. This can be useful for debugging purposes and can be used to plot the initial grid of an un-converged calculation to identify any specific problems with this. The additional .txt files are produced for each blade row in the calculation (row_0n_prefix.txt where n is the number of the blade row from the inlet). These can be used to define typical blade loading diagrams and incidence plots for each blade row. The Layout files for Tecplot that have been prepared in advance assume that the .txt file has the prefix “impeller”. Even if no .txt file is required, the prefix.txt file still must be specified in the vista_tf.fil file.

Interface Output Files (.int) If you request the generation of an interface file for another analysis program then the appropriate files are also generated. The first use of this has been established to allow a summary of the results to be obtained as input to an optimizing software system. A second option will be to generate the .stream file for MISES blade-to-blade calculations providing the streamtube thickness and the radius along a stream section. Even if no interface file is required, the .int file still must be specified in the vista_tf.fil file.

Screen Output Files (screen.scn) In normal operation, the progress of the program can be seen on the screen. If the command line includes a parameter -silent, the screen results will be written to a separate file called screen.scn and not to the screen. If this parameter is not present, this output goes to the screen. If a name follows this parameter, the screen results are printed to a file with this name.

Specification of the Control Data File (*.con) The control data file includes sections of text that help you to identify the parameters defined here. Note that if values are set to 0.0 or 0 then standard values are used, so typically you do not have to worry about this input. If zero values are specified for some parameters then the values actually selected by the program are written to the output file. Standard forms of this file are available for editing to meet the specific requirements, whereby in most cases no modification of the file is necessary. An example of a control data file is given in Appendix B: Example of a Control Data File (*.con) (p. 130). Section 1: Character strings identifying the control data (max 72 characters/line) The syntax is: Character string - title(1) Character string - title(2) Character string - title(3)

Section 2: Integer control parameters The syntax is: n_sl

max_it_main

max_it_mass

Parameter

Description

n_sl

Number of meridional streamlines Notes:

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•

Must be an odd number so that there is always a mid streamline.

•

Typically n = 9 or 17. If n_sl = 0, then 9 will be used.

•

Maximum n_sl = max_n_sl = 19.

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Screen Output Files (screen.scn) Parameter

Description •

If the mixing model is being used, (i_mix > 0 in section 4) then there has to be a minimum of 9 streamlines.

Maximum number of iterations of the main streamline curvature loop in the iterative method.

max_it_main

Notes: •

Typically specified as 500 but fewer are generally needed for simple radial compressor calculations to attain convergence.

•

If max_it_main < 4 then max_it_main = 4, so that at least 4 iterations are always done as a minimum.

•

If max_it_main = 0 then max_it_main = 500.

•

If the flow reaches the convergence limit before the maximum number of iterations is reached then the calculation is automatically stopped earlier.

Maximum number of iterations for internal mass flow loop at each quasi-orthogonal calculating station.

max_it_mass

Notes: •

Typically 10 and if max_it_mass = 0, then max_it_mass = 10.

•

If max_it_mass < 5 then max_it_mass = 5; experience shows that this is a sensible value.

•

If max_it_mass > 20 then max_it_mass = 20.

•

If the mass flow convergence tolerance at a particular quasi-orthogonal is reached before the maximum number of iterations are completed then mass flow iteration is stopped early.

Section 3: Integer control parameters that control input and output data The syntax is: i_print_plane

i_print_level

i_progress

i_display

i_restart

i_interface

Note that setting all of these parameters to 0 gives a standard form of output. Parameter

Description

i_print_plane

Determines the quasi-orthogonal calculating planes at which data is output into the results file. = 0, as i_print_plane = 4 = 1, output at no planes = 2, data at inlet and outlet planes only

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Vista TF Parameter

Description = 3, data at leading edges and trailing edges and inlet and outlet planes only = 4, data at all planes Note: The extent of the data printed at each plane is determined by i_print_level.

i_print_level

Determines the level of output data printed into the results file at each output plane. = 0, standard output (as iprint_level = 3) = 1, very limited data at each plane = 2, generous level of data at each plane = 3, extensive data at each plane Note: The planes at which output is available are defined by the parameter i_print_plane.

i_progress

i_display

Determines the extent of intermediate data that is printed to the various files. •

If i_progress = 0 then no intermediate information is printed.

•

If i_progress = 1 then intermediate progress of the iterations are printed to the history file.

•

If i_progress = 2 then data is printed to the history file and to the screen.

Determines extent of tabular data output which is prepared for displaying the results with other plot and post-processing tools: Notes:

i_restart

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•

If i_display = 1, then no plot files are produced.

•

If i_display = 0 then the output files of type .txt are produced for display of the results with Tecplot.

•

If i_display = 2, then a comma separated variable file with extension .csv is produced for display of the results with CFD-Post.

•

If i_display = 3, then both i_display = 0 and 2 above are activated.

•

Other output formats can be incorporated as requested.

Determines whether the restart file should be used and whether the results will overwrite the restart file contents. Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

Screen Output Files (screen.scn) Parameter

Description Notes:

i_interface

•

If i_restart = 0, the restart file (prefix.rst) will be used automatically if it is present (a warm start) and its content will be overwritten automatically at the end of a normal calculation. Note that this also overwrites the restart file even if the iterations are not converged, so that a second start with the same number of iterations starts with a better approximation. This is the normal way to use the program. The restart file includes the number of quasi-orthogonals and streamlines. If i_restart = 0 and this number has changed then the program makes a cold start with its own estimate of inititial conditions (as in i_restart = 1).

•

If i_restart = 1 the restart file (prefix.rst) will not be used even if it is available and the program will set up its own initial conditions (a cold start). The content of the restart file will be overwritten as under 1 above. This is not generally recommended but can be useful in debugging difficult cases. This is equivalent to deleting the existing restart file and using option 1 above.

•

i_restart = 2 and 3 are special options for running the program when coupled to an automatic optimizer. In these cases the use of a good restart file reduces the number of iterations needed and brings a reduction in calculating time. Unfortunately some of the geometries being examined may be poor and so it is inadvisable to overwrite the restart file with poor results. If i_restart = 2 then the file runs with a restart file called best_restart.rst and writes the results on to prefix.rst. If i_restart = 3 then the file runs with a restart file called best_restart.rst and also writes the results on to the same file best_restart.rst. In both cases if the restart file best_restart.rst is not present then the internal initial estimate is used (a cold start).

Determines the type of output interface file that is generated. Notes: •

If i_interface = 0 then no output interface file is generated.

•

If i_interface = 1 then the prefix.int file contains a summary of the results for use in radial compressor optimization.

•

Other options are in preparation, such as a link to the blade-to-blade program MISES.

Section 4: Integer control parameters for various models and reference parameters The syntax is: Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF i_expert

i_flow

i_fluid

i _inbc

i_mass

i_mix

i_ree

Parameter

Description

i_expert

Allows special calculations to be carried out making use of development features of the program. Normally you would set the value of this parameter to 0 or 1, but other expert features of the program may be modified with this control parameter. Each digit of the parameter has an influence on its effect. Notes: •

The last digit controls the choke calculation mode. Using a value of zero for the last digit causes the choke mass flow limitation to be eliminated which may be more robust in difficult cases. Calculations of new cases should start in this mode.

•

Using a value of 1 for the last digit, enables the choke mass flow limitation calculation. This requires exact data for the throat areas to be specified and should only be used if this is available. It is necessary to set this value to 1 when using iteration to pressure ratio in choked stages.

•

The second-last digit controls the blending function calculation for the deviation between the blade angle and the flow angle as follows: 0 - Turbines use departure angle at the leading and trailing edge ends, Compressors use swirl at the leading edge and departure angle at the trailing edge. 1 - Turbines and compressors use the departure angle for the leading and trailing edges. 2 - Turbines and compressors use departure angle at the trailing edge and relative swirl at the leading edge. 3 - Turbines and compressors use departure angle at the trailing edge and the absolute swirl at the inlet. 4 - Compressors use swirl at the leading edge and departure angle at the trailing edge; turbines use swirl at the outlet and departure angle at the leading edge. 5 - Compressors use swirl at the leading edge, departure angle at the trailing edge; turbines use swirl at the trailing edge and departure angle at the leading edge.

i_flow

Determines the input definition for the reference flow parameters (which are input in .aer file). Notes: •

78

i_flow = 0 then ref_mach, ref_phi, and ref_d, are specified, but if ref_mach > 3 then it is interpreted as

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Screen Output Files (screen.scn) Parameter

Description ref_u, so this is equivalent to ref_u, ref_phi, and ref_d. •

i_flow = 1 then ref_n, ref_mass, and ref_d are specified. Note: If there is more than one spool in the calculation with different rotational speeds, then this is taken into account as follows: - If i_spool = 2 and i_flow = 1 then ref_n1, ref_n2, ref_mass, and ref_d are specified. - If i_spool = 3 and i_flow = 1 then ref_n1, ref_n2, ref_n3, ref_mass, and ref_d are specified.

•

i_flow = 2 then ref_n, ref_volume, and ref_d are specified.

•

i_flow = 3 then ref_u, ref_mass, and ref_d are specified.

•

i_flow = 4 then ref_u, ref_volume, and ref_d are specified

•

i_flow = 5 then ref_n, ref_mass, and ref_d are specified together with the ref_pr (total to static pressure ratio between inlet plane and the last trailing edge on the mid-streamline). The value of ref_mass is a start value for mass flow in the iteration to pressure ratio and has no effect on the final solution.

•

i_flow = 6 then ref_n, ref_mass, and ref_d are specified together with ref_pr (total to static pressure ratio) together with n_p_te (the total number of trailing edges at which a guessed value of the static pressure ratio is specified, followed by the guessed pressure ratios at each trailing edge, including the last, which is also defined by ref_pr.

•

i_flow = 7 then ref_n, ref_mass, and ref_d are specified together with the ref_p (static pressure at the last trailing edge on the mid-streamline). The value of ref_mass is a start value for mass flow in the iteration to outlet pressure and has no effect on the final solution. This option may be useful for low speed devices where pressure ratio becomes indeterminate.

•

i_flow = 8 then ref_n, ref_mass, and ref_d are specified together with the ref_p (static pressure at trailing edge pane) together with n_p_te (the total number of trailing edges at which a guessed value of the static pressure is specified, followed by the guessed pressures at each trailing edge, including the last, which is also defined by ref_p.

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Vista TF Parameter

i_fluid

i_inbc

i_mass

Description •

i_flow = 9 then ref_n, ref_mass, and ref_d are specified together with the ref_cu (absolute swirl velocity at the last trailing edge on the mid-streamline). The value of ref_mass is a start value for mass flow in the iteration to outlet swirl and has no effect on the final solution. This option may be useful for turbine calculations where the last blade row is a turbine rotor.

•

Other options are available for debugging purposes.

•

The geometry definition of Vista TF assumes clockwise rotation. This leads to a certain convention for the sign of the blade angles (see Appendix A: A Note on Sign Convention for Angles and Velocities (p. 127)). In some cases you may have a counterclockwise machine with blade angles of the opposite sign. To avoid the need to change all the angles specified in the .geo file, an option is provided whereby the value of i_flow is given a negative sign.

Determines the model for the equation of state of the fluid: •

If i_fluid = 0 then ideal gas with constant specific heat.

•

If i_fluid = 1 then liquid.

Determines the type of inlet boundary conditions: •

i_inbc = 0 then input values are total pressure, total temperature and swirl (r x cu, that is radius times circumferential component of the absolute velocity) on the input plane.

•

i_in_bc = 1 then input values are total pressure, total temperature, and absolute flow angle.

Determines whether the mass flow is uniformly distributed across streamlines or not. •

i_mix

i_ree

Determines which mixing model is used: •

i_mix = 0 then no mixing model.

•

i_mix = 1 then a spanwise mixing model based on eddy diffusion across the streamlines will be used. Note that this requires a minimum of 9 streamlines (n_sl => 9).

Determines the form of the radial equilibrium equation that is used to determine the velocity gradient along the quasiorthogonal. •

80

i_mass = 0 then mass flow between each streamline is the same.

i_ree = 0 then the equations as given in the paper of Casey and Roth (1984) are used, except that the dissipation term is set to zero and the blade force term is set to zero at a trailing edge and at a leading edge.

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Screen Output Files (screen.scn) Parameter

Description •

i_ree = 1 then the solution is as for i_ree = 0 but the dissipation term is not set to zero but the equations as given in the theory documentation are used.

•

i_ree = 2 then the dissipation term is not set to zero but the equations given in the paper of Casey and Roth (1984) are used.

•

i_ree = 3 then the velocity gradient in the radial equilibrium equation is reduced by the factor grad_ree given in section 5. This is useful for debugging difficult cases and the simulation becomes similar to a mean-line calculation with no gradient of meridional velocity across the span. If grad_ree = 1.0 then selecting i_ree = 3 has no effect.

Section 5: Convergence and damping factors The syntax is: damp_sc

damp_vl

cm_start

tolerance_cm

tolerance_mass

grad_ree

The damping factor model automatically chooses the most appropriate values of these parameters based on the type of machine and the grid. You would typically specify the following values for this section: 0.00 0.00 0.00 0.00 0.00 1.00

Parameter

Description

damp_sc

Damping factor for streamline curvature terms. Note: •

The Wilkinson stability analysis for streamline curvature programs indicates that the streamline curvature damping term has to be reduced for long closely spaced quasi-orthogonals (high aspect ratio). For details, see the section on computational grid (Computational Grid (p. 144)).

•

If damp_sc = 0.0 then the program determines the value of damping factor from the theory of Wilkinson, or uses 0.25, whichever is smaller.

•

Typically values of damp_sc between 0.05 and 0.25 are used, but lower values may be necessary for high aspect ratio quasi-orthogonals (as in end stages of steam turbines).

•

If the specified value of damp_sc is larger than the value predicted by the Wilkinson stability theory then the program automatically reduces the damping factor to a stable value.

•

If the program has convergence problems with an increasing error then the value is automatically reduced internally within the program during the convergence process.

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81

Vista TF Parameter

Description •

damp_vl

Several different schemes for the damping are applied. The original scheme is obtained with a value of damp_sc between 1.0 and 1.25. New schemes which are more stable and robust in most cases can be obtained with the value of damp_sc between 0.0 and 0.25. A value between or 2.0 and 2.25 uses the original scheme with changed constants. The first digit then defines which scheme is used (0 - original, 1 - modified original, 2 - new scheme) and the digits after the decimal point are the damping factor itself.

Damping factor on velocity level. Note this damping factor is also used internally in the program for all parameters which are under-relaxed. Notes:

cm_start

•

There is no stability theory to define this, and a typical value used is 0.50, indicating that 50% of the new parameter together with 50% of its original value is used.

•

If damp_vl = 0.0 then 0.50 is used.

Value of meridional velocity on the mean streamline as a fraction of u_ref, as used in the initial conditions. This is then a sort of flow coefficient (cx/u) of the device concerned and is used as a guide to the velocity levels that can be expected. Notes:

tolerance_cm

•

Recommended that this should be less than the actual value when converged because this avoids choking during the early streamline curvature iterations.

•

If simulations from a cold-start (with no restart file) fail to converge, it may be useful to modify this parameter because it strongly influences the start velocities.

•

Not used if the restart initial condition is used.

•

If cm_start = 0.0 then 0.25 is used for all calculations except radial turbines where 0.1 is used. The value of 0.25 is probably adequate for radial compressors only.

Tolerance level on change in meridional velocity during streamline curvature iterations. The value specified is the maximum percentage change in meridional velocity for convergence. Iterations stop when all streamlines and all quasiorthogonals have a lower value than this. Notes:

82

•

Typical value 0.01 (that is, 0.01%, which is 1 part in 10,000).

•

If tolerance_cm = 0.0 then 0.01% is used.

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Screen Output Files (screen.scn) Parameter

tolerance_mass

Description •

Note that if the meridional velocity is low at a certain point in the flow field, it may be necessary to use a higher value than this.

•

Note that the extremely low value of 0.01% does not imply that the solution is as accurate as this, but just provides confidence that convergence has really been achieved.

Tolerance level on mass flow for internal mass flow iteration. Note that because this controls the convergence of the innermost loop, it should be a factor of 2 to 10 lower than the tolerance value for the meridional velocity (above). Notes:

grad_ree

•

Typical value 0.001 (that is 0.001%, which is 1 part in 100000).

•

If error_max = 0.0 then 0.001% is used.

Factor to reduce the spanwise velocity gradient from the radial equilibrium equation. Normally equal to 1.0 indicating that the gradient from the radial equilibrium equation is used without change. For calculations with i_ree = 3, if grad_ree is set to 0.0, the program takes a meridional velocity gradient of 0.0 (that is constant meridional velocity across the span) and a value between 1.0 and 0.0 reduces the spanwise gradient of meridional velocity determined by the radial equilibrium equation by this amount.

Specification of the Geometry Data File (*.geo) The geometry data file includes sections of text lines that help you to identify the parameters defined here. You should read the section on geometry in Appendix A: A Note on Sign Convention for Angles and Velocities (p. 127) to become familiar with sign conventions and angle definitions used in this file. An example of a geometry data file is given in Appendix C: Example of a Geometry Data File (*.geo) for a Radial Impeller (p. 130). Section 1: Character strings identifying the geometry data (max 72 characters/line) The syntax is: Character string - title(1) Character string - title(2) Character string - title(3)

Section 2: Number of quasi-orthogonal lines and scale factor (one line) The syntax is: n_qo

scale

Parameter

Description

n_qo

n_qo = number of quasi-orthogonal lines from inlet to outlet of the domain. From version V1.31 onwards the maximum value of this parameter is unlimited.

scale

The scaling factor for all geometry data that is input. Notes: Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

83

Vista TF Parameter

Description •

Usually the geometry data is input in SI units (that is, all values are expected in m and not mm) and then this value is 1.0.

•

If the input geometry data comes from a CAD system then it may be in mm. In this case, the value of scale must be 0.001. Similarly the value can be adjusted to allow the geometry data to be input in other systems of units; for example, inches.

•

This scale factor only scales the data in the geometry input file and has no effect on other dimensions elsewhere; for example, it does not scale the reference diameter, which must be input with units of metres, in the aerodynamic file.

•

If you specify scale = 0.0, unity is used.

For each quasi-orthogonal, the following data is required to define the flow channel for the meridional through-flow calculation and the meridional spacing of the quasi-orthogonals. Note that some of this data is also repeated in the section on the blade geometry. This duplication allows calculations to be made in a channel that is not the same as the hub and casing line of the actual blade definition (blade cropping). Section 3: Definition of quasi-orthogonal types and end points (n_qo lines: i = 1 to n_qo) The syntax (of a single line) is: i

r_hub(i)

r_shr(i)

z_hub(i)

z_shr(i)

n_blade(i)

Parameter

Description

i

Number of a particular quasi-orthogonal line.

n_curve(i)

i_type(i)

Notes: •

The actual value is not used by the program internally because it recounts the quasi-orthogonals as they are input. The number specified is only used as a guide to the location in the input file.

•

This allows you to merge two different geometry files of, say, a rotor and stator, to a single stage geometry file without the need to renumber the quasi-orthogonals. In this case, the same number may appear more than once. In a similar way, a single quasi-orthogonal may be removed without the need for renumbering the lines.

r_hub(i)

Radial coordinate at hub end of quasi-orthogonal [m].

r_shr(i)

Radial coordinate at casing end of quasi-orthogonal [m].

z_hub(i)

Axial co-ordinate at hub end of quasi-orthogonal [m].

z_shr(i)

Axial co-ordinate at casing end of quasi-orthogonal [m]. Notes on co-ordinates: •

84

r_hub may not be close to zero; adapt the grid if necessary to avoid small values of r_hub.

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i_row(i)

i_spool(i)

Screen Output Files (screen.scn) Parameter

n_blade(i)

Description •

The aspect ratio of the quasi-orthogonal lines determines the stability of the solver. The lines should not be too closely spaced.

•

The end coordinates of the leading and trailing edges of blade rows should be included in the list of coordinates.

•

The end coordinates of the leading edge of a splitter vane should be included in the list of coordinates.

Number of blades in blade row. Notes:

n_curve(i)

•

= 0 in duct regions.

•

The number of blades changes at a splitter blade leading edge in a compressor or at a splitter vane trailing edge in a turbine, and changes again for multiple splitters. This is the only information that the program has about the splitters, so the location of the splitter vane leading or trailing edge needs to be a quasi-orthogonal line in the input data.

Number of defining points along the ith quasi-orthogonal line. Notes:

i_type(i)

•

= 1, a special case for duct stations. This indicates that there are 2 defining points (as for n_curve(i) =2) but that no further information for this calculating station is provided in section 4 below, because it is already fully defined by the hub and casing points given in section 3.

•

= 2 for a linear calculating plane in which only the end points of the quasi-orthogonal are defined. In this case, similar information can be found in section 4.

•

> 2 for a non-linear or curved calculating plane.

•

The number of defining points can vary from station to station but n_curve(i) should typically be the same for all stations because streamline section data is usually available on a fixed number of spanwise sections.

•

Note that the hub and casing geometry information does not necessarily have to be the same as that defined in section 4. In this case the data in section 3 will be used to crop the blade row or to make a section through the blade information in section 4.

Parameter to identify type of calculating station: 1 - for duct region 2 - for non-rotating blade row (stator) 3 - for rotating blade row (rotor) Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

85

Vista TF Parameter

Description Notes:

i_row(i)

•

The program internally identifies which lines are leading and trailing edges from the changes of type of blade row, and which line is the leading edge of a splitter vane (by the change in blade number).

•

There must be at least two duct calculating stations upstream of the first blade row, and downstream of the last blade row.

•

A blade row must consist of at least two calculating stations (leading and trailing edge). Typically a radial impeller will have around 15 calculating stations, because this gives a 6° turn between each station and improves the calculation of the curvature terms.

•

There must be at least two blade calculating stations upstream and downstream of a splitter vane leading edge.

•

Other types of blade row may be defined at a later stage.

This parameter is used to identify type of blade row and stage of the quasi-orthogonal calculating station. In fact the program can usually identify the type of blade row itself from the geometry and the context, so it is not necessary to specify these values at all and, in the first instance, this parameter may be set to zero. They are included here for special cases where the program may have difficulty with the rules that are coded to identify blade row types. = n11 - radial compressor inlet guide vane1 = n12 - radial compressor inlet guide vane2 = n13 - radial compressor impeller blade = n14 - radial compressor diffuser vane = n15 - radial compressor return channel vane = n16 - radial compressor axial de-swirl vane = n21 - axial compressor inlet guide vane1 = n22 - axial compressor inlet guide vane2 = n23 - axial compressor rotor blade = n24 - axial compressor stator vane = n25 - axial compressor outlet guide vane = n31 - radial turbine inlet guide vane1 = n32 - radial turbine inlet guide vane2

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Screen Output Files (screen.scn) Parameter

Description = n33 - radial turbine impeller blade = n34- radial turbine stator vane = n35- radial turbine outlet guide vane = n41 - axial turbine inlet guide vane1 = n42 - axial turbine inlet guide vane2 = n43- axial turbine rotor blade = n44- axial turbine stator vane, = n45- axial turbine outlet guide vane Notes: The value of n determines which stage is being considered, such that a multistage axial compressor with an IGV would begin with values of 121 for the inlet guide vane, continue with values of 123 for the rotor, and 124 for the downstream stator, so that the next rotor would be 223, an so on. A double row of stators would be denoted as n24 and n25 for the successive blade rows.

i_spool

Parameter to identify rotational speed of spool or shafts where different blade rows have different speeds. 0 single shaft with one speed (ref_n) 1 first shaft with speed (ref_n1) 2 second spool with second speed (ref_n2) 3 third spool with third speed (ref_n3) Note that counter-rotating blade rows can be dealt with by specifying negative speeds for the second spool. The program determines the number of different spools (n_spool) from the number of different values of i_spool(i) found in the geometry input file. (The maximum is set to be 3.)

Notes: •

The data is supplied on n_curve lines spaced fairly evenly from hub to casing. For example, if n_curve = 5, there may be points at 0%, 25%, 50%, 75%, and 100% of span. If n_curve = 2, there will be just two points, at 0% and 100% span.

•

The blade data and quasi-orthogonal data in section 4 may extend outside of the flow channel defined by the meridional coordinates given in section 3. In a normal calculation, the data overlaps partly with that given in section 3, because the end points of the quasi-orthogonal lines are defined twice (except for duct calculating stations with n_curve(i) = 1; see above). The flow channel defined in section 3 is generally congruent with the blade hub and shroud defined in section 4. The blade, as defined in section 4, may extend outside of the region of the flow channel because this Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

87

Vista TF allows a calculation to be made in a cropped or trimmed flow channel only by changing the data in section 3; section 4 does not need to be changed. •

The end points of the quasi-orthogonal lines, as defined by coordinates r_hub(i), r_shr(i), z_hub(i), and z_shr(i), should lie along the quasi-orthogonal lines as defined by r_qo (j,i) and z_qo(j,i) below. In many cases, the end points will be coincident with the blade data, but if this is not the case, it is not acceptable to define end points that do not lie on the blade data point.

•

All the angles are specified in degrees because this is more convenient in those cases where it may be necessary to define the geometry by hand, and also allows a simple consistency check, but internally the program converts them into radians. Further description of the angles is provided in Appendix A: A Note on Sign Convention for Angles and Velocities (p. 127). The sections above define only the hub and casing walls and provide information on the type of calculating station. The detailed orientation and position of the curved quasi-orthogonal line and the details of the blade surface geometry are provided in the next section.

Section 4: Geometry of quasi-orthogonal line and blade The syntax (of the single line) is: i

j

r-qo(j,i)

theta_qo(j,i)

z_qo(j,i)

thu_qo(j,i)

gamma_r_qo(j,i)

Parameter

Description

i

Number of a particular quasi-othorgonal for data input (increasing from inlet to outlet). Note that this value is not read in as input data but is simply used as orientation in the data file when examining the geometry input data.

j

Number of streamline for data input (increasing from hub to shroud). Note that this value is not read in as input data but is simply used as orientation in the data file when examining the geometry input data. Note that for each q-o (i), the spanwise data is entered (j) before continuing with the next q-o.

r_qo(j,i)

Radial coordinate of point j along q-o (i) [m].

theta_qo(j,i)

Circumferential coordinate of blade camber line at point (r_qo, z_qo) [degrees]. Note:

88

•

The angular coordinate (theta) is taken as positive in the direction of rotation and negative in the other direction.

•

In a duct region this angle may be zero.

•

This angle is not used by the program but helps to visualize the blade shape and may be useful for plots of the blade shape.

•

In a region where there is a splitter vane this angle is the blade camber angle of the main blade and not of the splitter.

z_qo(j,i)

Axial coordinate of point along quasi-orthogonal [m].

thu_qo(j,i)

Circumferential thickness of blade at point (r_qo, z_qo) [m].

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gamma_z_qo(j,i)

Screen Output Files (screen.scn) Parameter

Description Note: •

In a duct region this thickness should be specified as zero.

•

In a region where there is a splitter vane this thickness is the mean thickness of the main blade and the splitter.

•

At leading and trailing edges the value supplied is not used by the program, but the calculating station is taken to be at the limit of the chord with zero thickness.

•

The thickness is not the thickness normal to the camber line.

gamma_r_qo(j,i)Lean angle of the blade with a radial line [degrees] as defined in Appendix A: A Note on Sign Convention for Angles and Velocities (p. 127). gamma_z_qo(j,i)Lean angle of the blade with an axial line [degrees] as defined in Appendix A: A Note on Sign Convention for Angles and Velocities (p. 127). Notes: •

This geometry includes the coordinates of the blade camber surface (r-qo(j,i), theta_qo(j,i), z_qo(j,i)) so that it would theoretically be possible for the program to differentiate this information to determine the slope angles of the surface (gamma_r_qo(j,i), gamma_z_qo(j,i)). This is not done for two reasons. Firstly, experience shows that with the crude grids typically used for throughflow calculations, this differentiation would be an unwanted source of error leading to poor estimates of the blade angles, so a system was chosen in which the blade angles are supplied. In fact the value of theta_qo(j,i) is not used by the program and can be specified as zero. Secondly, in many cases the slope angles of a blade row are known (inlet and outlet angles) whereas the circumferential coordinate is unknown.

•

This system of geometry with the definition of two angles is designed for radial turbomachinery applications because it allows the complex shape of three-dimensional blades to be defined by the use of the two lean angles, gamma_r and gamma_z.

•

In conventional axial turbomachinery throughflow programs, it is not usual to define the blade in much detail because often simulations are carried out with only inlet and outlet blade angles. This is also possible with Vista TF. In a ductflow calculation with only leading and trailing edges, the value of gamma_r can be set to 0°. Because the leading and trailing edges are not considered to have any blade force, this has no effect on the simulation. The value of gamma_z defines the inlet and outlet blade angles of sections through the blade at constant radius.

•

Vista TF assumes that the geometry is always specified for a clockwise rotation (see Appendix A: A Note on Sign Convention for Angles and Velocities (p. 127)). If the geometry is correctly specified, a negative rotational speed is used, and Vista TF performs calculations assuming that the shaft is rotating in the wrong direction with all the wrong incidences, loading, an so forth. For the case where the geometry is specified for counterclockwise rotation, the value of i_flow in the .con file should be specified as a negative number, for example, -1 or -2. This causes the program to internally switch the angles from positive to negative, and vice-versa, before it proceeds to perform calculations as usual, assuming that the shaft rotates in the clockwise rotation.

•

The next sections provide additional blade-row geometry data for use by the correlations in the program. Although this data is not always needed, the format of this section includes 8 real parameters. Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

89

Vista TF Section 5: Additional geometry data (n_curve(i) lines for each blade row) The syntax is: j

throat

throat_pos

clearance

max_thickness

te_thickness

dummy

Parameter

Description

j

Number of a particular streamline for data input (increasing from hub to shroud).

throat

Throat width of section j [m]. Note:

throat_pos(i)

•

If the value of zero is input then the program estimates the throat width from the blade angles and the blade thickness, taking into account that the throat is close to the leading edge for compressors and close to the trailing edge for turbines. For radial compressors this estimate is not particularly accurate and for cases close to choke you should provide more precise data here.

•

For axial compressors it is assumed that the blade has a circular arc camber line and the program includes an estimate of the throat area based on the geometrical relationships for circular arc blades.

•

For other blade types, you should specify the value.

Position of throat on this blade section. Note: •

If the value of zero is input then the program estimates the throat position from the blade angles and the blade thickness, taking into account that it is close to the leading edge for compressors and close to the trailing edge for turbines.

•

For radial compressors this estimate is not particularly accurate and for cases close to choke you should provide more precise data here.

•

For axial compressors it is assumed that the blade has a circular arc camber line and the program includes an estimate of the throat position based on the geometrical relationships for circular arc blades.

•

For other blade types, you should specify the value.

tip clearance

Tip clearance of hub section [m].

hub/shroud

Tip clearance of shroud section [m]. Note:

90

•

If the first value is non-zero, this is interpreted as the hub clearance.

•

If the last value (n_curve(i)) is non-zero, this is interpreted as the casing clearance.

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dummy

dummy

Screen Output Files (screen.scn) Parameter

Description •

max_thickness

In a variable stator vane with a hub clearance and a clearance gap for the shaft, it is possible to have non-zero values on both the hub and the tip and then both will be taken into account in the loss correlations.

Maximum normal thickness of blade section [m]. Note:

te_thickness

•

Although the circumferential thickness of the blade row is already specified in section 3, the location of the quasiorthogonal lines may not coincide with the location of normal maximum thickness, so this value must be specified separately.

•

If the value of zero is specified then the program searches for the normal maximum thickness of the blade, as given in section 3, and uses it.

Trailing edge normal thickness of blade section [m]. Note:

dummy

•

Although the circumferential thickness of the blade row is already specified in section 3, this value must be specified separately.

•

If the value of zero is specified then the program estimates the trailing-edge thickness of the blade from the circumferential thickness given in section 3, and uses it.

In order to allow for parameters that may be needed by other correlations in the future, the program includes three dummy parameters which should each be set to 0.0.

Specification of Aerodynamic Data File (*.aer) The aerodynamic input data file includes lines of text that help you to identify the parameters defined here. Although in some areas this file may appear to be complex, a typical simulation uses only one of the allowed options and so, once an input file with the correct format has been established, further use of the file is less complex. An example of an aerodynamic data file is given in Appendix D: Example of an Aerodynamic Data File (*.aer) (p. 132). Section 1: Character strings identifying the aerodynamic data (max 72 characters/line) The syntax is: Character string – title(1) Character string – title(2) Character string – title(3)

Many options are supplied for specifying the flow data, but typically the options with i_flow = 1 (specified mass flow) and i_flow = 5 (specified pressure ratio) are used. Note that i_flow is specified in the control file. Section 2: Reference aerodynamic parameters (depends on value of i_flow in .con file) The syntax is: Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

91

Vista TF ref_mach

ref_phi

ref_d

if i_flow = 0 and ref_mach < 3, or ref_u

ref_phi

ref_d

if i_flow = 0 and ref_u > 3, or ref_n

ref_mass

ref_d

if i_flow = 1 and n_spool = 0 or 1, or ref_n1

ref_n2

ref_mass

ref_d

if i_flow = 1 and n_spool = 2, or ref_n1

ref_n2

ref_n3

ref_mass

ref_d

if i_flow = 1 and n_spool = 3, or ref_n

ref_volume

ref_d

if i_flow = 2, or ref_u

ref_mass

ref_d

if i_flow = 3, or ref_u

ref_volume

ref_d

if i_flow = 4, or ref_n

ref_mass

ref_d

ref_pr

ref_d

ref_pr

ref_d

ref_pd

ref_d

ref_pd

ref_d

ref_cu

if i_flow = 5, or ref_n

ref_mass

n_p_te

guess_pr_1

...

n_p_te

guess_pd_1

...

if i_flow = 6, or ref_n

ref_mass

if i_flow = 7, or ref_n

ref_mass

if i_flow = 8, or ref_n

ref_mass

if i_flow = 9.

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Screen Output Files (screen.scn)

Note The very large number of possible ways of specifying the flow and speed appears, at first, to be slightly overwhelming. Generally i_flow = 1 is used. Note that the reference diameter is given here and not in the geometry file. This is because you may prefer to use the hub diameter, the tip diameter, the inlet diameter, or the outlet diameter, as a reference value without changing the geometry file.

Note The geometry definition of Vista TF assumes clockwise rotation. This leads to a certain convention for the sign of the blade angles (see Appendix A: A Note on Sign Convention for Angles and Velocities (p. 127)). In some cases you may have a counterclockwise machine with blade angles of the opposite sign. To avoid the need to change all the angles specified in the .geo file, an option is provided whereby the value of i_flow is given a negative sign. A negative value for speed means that the blade is rotating in the counterclockwise direction.

Parameter

Description

i_flow=0

“Iteration to mass flow” ref_mach = Machine Mach number (based on inlet total conditions) [-] or reference blade speed [m/sec]. (In this document, “[-]” means dimensionless.) Notes: •

If ref_mach < 3 then ref_mach is interpreted as ref_mach.

•

If ref_mach > 3 then ref_mach is interpreted as ref_u.

ref_phi = Inlet flow coefficient (based on total inlet conditions) [-]. (In this document, “[-]” means dimensionless.)

ref_d = Reference blade diameter for the definition of flow coefficient. i_flow=1

[m]

“Iteration to mass flow”

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Vista TF Parameter

Description ref_n = Machine rotational speed [rpm] ref_mass = Mass flow [kg/sec] ref_d = Reference blade diameter for the definition of flow coefficient.

[m]

If the machine has separate spools of different speeds (i_spool(i) > 2) then the speed of each spool can be provided up to a maximum of three different spools. ref_n1 = Rotational speed of shaft 1 [rpm] ref_n2 = Rotational speed of shaft 2 [rpm] ref_n3 = Rotational speed of shaft 3 [rpm] Counter-rotating blade rows require the second blade row to be provided with a negative speed. i_flow=2

“Iteration to mass flow” ref_n = Machine rotational speed [rpm] ref_volume = Volume flow at inlet total conditions [m3/sec] ref_d = Reference blade diameter for the definition of flow coefficient.

i_flow=3

[m]

“Iteration to mass flow” ref_u = Reference blade speed [m/s] ref_mass = Mass flow [kg/sec] ref_d = Reference blade diameter for the definition of the blade speed [m]

i_flow=4

“Iteration to mass flow” ref_u = Reference blade speed [rpm] ref_volume = Volume flow at inlet total conditions [m3/sec] ref_d = Reference blade diameter for the definition of the blade speed [m]

i_flow=5

“Iteration to pressure ratio” ref_n = Machine rotational speed [rpm] ref_mass = Mass flow [kg/sec] (estimate of actual mass flow but final converged mass flow is determined by the pressure ratio and this only serves as an initial guess)

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Screen Output Files (screen.scn) Parameter

Description ref_d = Reference blade diameter for the definition of flow coefficient.

[m]

ref_pr = Total to static pressure ratio on mean streamline i_flow=6

“Iteration to pressure ratio” ref_n = Machine rotational speed [rpm] ref_mass = Mass flow [kg/sec] (estimate of actual mass flow) ref_d = Reference blade diameter for the definition of flow coefficient.

[m]

ref_pr = Total to static pressure ratio on mean streamline n_p_te = Number of trailing edges at which a guessed value of the pressure ratio is specified guess_pr_1 = Guessed value of the pressure ratio at the first trailing edge guess_pr_2 = Guessed value of the pressure ratio at the second trailing edge ... guess_pr_n_p_te = This continues up to and including the last trailing edge. Note that if the pressure ratio of the last trailing edge differs to that of ref_pr, than all values at all trailing edges are scaled with the value of ref_pr. i_flow=7

“Iteration to pressure difference” ref_n = Machine rotational speed [rpm] ref_mass = Mass flow [kg/sec] (estimate of actual mass flow but final converged mass flow is determined by the pressure ratio and this only serves as an initial guess) ref_d = Reference blade diameter for the definition of flow coefficient.

[m]

ref_pd = Total to static pressure difference on mean streamline i_flow=8

“Iteration to pressure difference” ref_n = Machine rotational speed [rpm]

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Vista TF Parameter

Description ref_mass = Mass flow [kg/sec] (estimate of actual mass flow) ref_d = reference blade diameter for the definition of flow coefficient

[m]

ref_pd = Total to static pressure difference on mean streamline n_p_te = Number of trailing edges at which a guessed value of the pressure ratio is specified guess_pd_1 = Guessed value of the pressure difference at the first trailing edge guess_pd _2 = Guessed value of the pressure difference at the second trailing edge ... guess_pd_n_p_te = This continues up to and including the last trailing edge i_flow=9

“Iteration to outlet swirl” ref_n = Machine rotational speed [rpm] ref_mass = Mass flow [kg/sec] (estimate of actual mass flow) ref_d = reference blade diameter for the definition of flow coefficient.

[m]

ref_cu = Swirl velocity on mean streamline at rotor outlet

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Screen Output Files (screen.scn)

Note •

The reference blade speed, tip speed Mach number, or Machine rotational speed is also needed for the calculation of a stator blade row. This is because these parameters are used to define various non-dimensional flow and work coefficients and the reference blade speed is also used to determine the flow velocities for the initial estimate of the flow field (together with parameter cm_start. See section 5 of the .con file specification given in Specification of the Control Data File (*.con) (p. 74)).

•

Iteration to a defined pressure ratio makes use of the so-called target pressure ratio method of Denton. This requires the program to make a fist guess of the pressure at each trailing edge of the machine. The algorithm currently incorporated makes a crude estimate of these, but it has been found that this may not be sufficient to secure convergence. For this reason, you can define the first guess of the pressure at each trailing edge by setting i_flow = 6 (instead of 5).

•

A line prepared with data for i_flow = 6 can formally also be used with i_flow = 5 or i_flow =1 with no change, so that a calculation can switch from “iteration to pressure ratio” to “iteration to mass flow” with no formal change to the aerodynamic input data file.

Section 3: Reynolds number or viscosity The syntax is: ref_re

or ref_mue

Parameter ref_re

ref_mue

Description ), ref_D ( ), Reynolds number based on ref_u ( and inlet total conditions [-]. (In this document, “[-]” means dimensionless.)

Dynamic viscosity conditions.

at the inlet plane and mean inlet total

Note The program identifies which of these parameters has been provided from the absolute value of the numerical input. If the value is greater than 1.0 [N s m^-2] (or equivalent value in other units), it is interpreted as a Reynolds number; if it is less than 1.0 [N s m^-2] but greater than 0.0000001 [N s m^-2], it is interpreted as the dynamic viscosity. A value of 0 causes the program to determine the dynamic viscosity from an inbuilt equation for the dynamic viscosity based on Sutherland’s law and the inlet total temperature.

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Vista TF

Section 4: Fluid data (depends on value of i_fluid in .con file) The syntax is: cp_gas

gamma_gas

if i_fluid = 1, which indicates an ideal gas, or cw_fluid

rho_fluid

if i_fluid = 2, which indicates a liquid. Parameter

Description

i_fluid = 1

cp_gas = Specific heat at constant pressure [J/kgK]

(ideal gas) gamma_gas = ratio of specific heats [-] (In this document, “[-]” means dimensionless.)

i_fluid = 2

cw_fluid = Specific heat of fluid [J/kgK]

(liquid) rho_fluid = density of liquid [kg/m3]

Section 5: Number of points on the inlet boundary where flow conditions are specified The syntax is: n_inbc

Parameter

Description

n_inbc

Number of points at which the inlet flow conditions are specified across the inlet plane. Note: •

n_inbc < n_sl

•

if n_inbc = 1 then only a single value is input and the values are constant across the span

Section 6: Fraction of mass flow where inlet conditions are specified (n_inbc values) The syntax is: f_mass_inbc

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Screen Output Files (screen.scn) Parameter

Description

f_mass_inbc

n_inbc values of the fraction of mass along the inlet boundary at which inlet boundary conditions are specified. First value should be 0.0 and last value should be 1.0. Note that if n_inbc = 1 then this has no function and a dummy value can be specified, but this should not be omitted.

Section 7: Pressure on the inlet boundary (n_inbc values which depend on i_inbc in .con file) The syntax is: pt_inbc

if i_inbc = 0. Parameter

Description

pt_inbc

Total pressure on the inlet boundary [Pa].

(i_inbc=0)

Note that if an incompressible calculation is carried out it is still necessary to specify the absolute value of the total pressure on the inlet boundary.

Section 8: Temperature on the inlet boundary (n_inbc values, depend on i_inbc in .con file) The syntax is: tt_inbc

if i_inbc = 0. Parameter

Description

tt_inbc

Total temperature on the inlet boundary [K].

(i_inbc = 0)

Section 9: Swirl or angle on the inlet boundary (n_inbc values, depend on i_inbc in .con file) The syntax is: rcu_inbc

if i_inbc = 0, or alpha_inbc

if i_inbc = 1. Parameter

Description

rcu_inbc

Swirl on the inlet boundary [m2/sec]. Note that this is the product of the local radius of the streamline and the local circumferential velocity component and is positive if the swirl is in the forward direction of rotation.

(i_inbc=0)

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Vista TF Parameter

Description

alpha_inbc

Flow angle on the inlet boundary [°]. Note that this is from the axial direction and positive in the direction of rotation. Note also that, if a single value is specified, it is used to calculate the swirl on the mean streamline of the inlet boundary, and this swirl is then kept constant across the span. If a constant angle across the span is required then 2 values need to be specified across the span (n_inbc=2). Experience with radial turbines with high swirl at the inlet show that the specification of a single value of swirl across the span is more robust than specifying a variation of flow angle across the span.

(i_inbc=1)

Section 10 : Aerodynamic model parameters The syntax is: eddy

f_bl_le

f_bl_te

Parameter

Description

eddy

Spanwise mixing parameter (eddy diffusivity). Notes:

100

•

Typically 0.0001 to 0.001. See Streamline Curvature Throughflow Theory (p. 118).

•

This has no function if i_mix = 0.

•

If i_mix = 1 and eddy = 0.0 then a value of eddy = 0.0005 will be used.

f_bl_le

f_bl_te is the meridional fraction of blade length at the leading edge where the blade is partly transparent to the flow (accounts artificially for the increased loading due to incidence). It is recommended that you specify a value of 0.0 for both f_bl_te and f_bl_le. If both f_bl_te and f_bl_le are equal to zero then the program estimates the values of these from the blade spacing using the equations given in Streamline Curvature Throughflow Theory (p. 118). If you want, you can specify these values. If you specify 0.0 then the flow is congruent with the mean blade camber line at the leading edge. A typically value is roughly equal to the blade spacing.

f_bl_te

Fraction of blade length after which the blade is partly transparent to the flow at the trailing edge (accounts artificially for the decreased loading due to deviation as the trailing edge is approached). It is recommended that you specify a value of 0.0 for both f_bl_te and f_bl_le. If you specify 1.0 then the flow is congruent with the mean blade camber line right up to the trailing edge. If both f_bl_te and f_bl_le are equal to zero then the program estimates these from the blade spacing using the equations given in Streamline Curvature Throughflow Theory (p. 118).

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Screen Output Files (screen.scn)

Specification of Correlations Data File (*.cor) The input data file includes sections of text lines that help you to identify the parameters defined here; see the examples in Appendix E: Examples of Correlations Data Files (*.cor) (p. 133). The first part of the file contains control parameters that define the layout of the remainder of the input data that is needed. The file is arranged so that it always has a standard format at the beginning (first 8 lines) but may require different data towards the end depending on the type of calculation under consideration (axial compressor, radial turbine, single stage, multi-stage, an so on). Similar types of simulations always use similar formats for this file, but different types of simulations may require different formats for the latter part of this file. You specify the empirical data using one of two approaches: •

You specify losses, blockage, and deviation, associated with individual, specifically-defined, quasi-orthogonals. This approach is oriented around the quasi-orthogonals, enabling you to specify different local efficiency and blockage values for each quasi-orthogonal. Although deviation is only meaningful at the trailing edge, a similar approach is used for deviation to be consistent with losses and blockage. This approach is recommended for beginners.

•

You provide information that enables the program to calculate the needed empirical data for blade rows from built-in correlations. This approach is oriented around blade rows and requires data to be specified at each blade row trailing edge (or upstream of this – see later).

Note that the correlations used for individual blade rows can be changed from one blade row to another. You can also use the correlations for deviation from one source and the correlations for losses from another. In general, and for simplicity, you should apply the correlations in such a way that all blade rows use the same correlations and the losses, blockage, and deviation, are also from the same source. The correlations currently programmed and in preparation can be obtained with the use of the following parameters for i_loss_type, i_dev_type and i_ewb_type: Turbine correlations

i_loss_type / i_dev_type / i_ewb_type

Kacker-Okapuu

1/1/1

Dunham-Came

2/2/2

Compressor correlations

i_loss_type / i_dev_type / i_ewb_type

Miller-Wright

11 / 11 / 11

Miller-Wright (as modified by Calvert)

12 / 12 / 12

If required, you can specify single values of the losses, deviation, and blockage parameters, for the first blade row or first quasi-orthogonal. These are then used throughout the domain provided that they are not changed again. In addition, it is possible to apply multiplicative and additive correction factors to the values predicted by the correlations, by the application of “fudge factors” (user-defined corrections). Generally this file does not need to be changed once it has been set up, so you might not need to understand all the intricacies of

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Vista TF the many possibilities that it allows, and typically a standard type of correlations file can be established which can then be used for all subsequent simulations with the same set of correlations. Examples of some typical correlations data files are given in Appendix E: Examples of Correlations Data Files (*.cor) (p. 133), showing several specific examples for specific types of calculation. Section 1: Character strings identifying the correlation data (max 72 characters/line) The syntax is: Character string – title(1) Character string – title(2) Character string – title(3)

Section 2: Integer control parameters for loss, deviation and blockage models (one line) The syntax is: i_loss

i_dev

i_ewb

Parameter

Description

i_loss

Determines the loss specification to be used. Notes: •

i_loss = 0 No losses are specified and the calculation uses constant entropy. Note, however, that in order to retain similar structures for the correlations file, the lines described in sections 3 and 4 are still needed, but have no effect.

i_dev

•

If i_loss = 1 then a user-defined variation of efficiency, loss coefficient, or dissipation coefficient across the span is specified at the spanwise positions given in section 4. The number of definition positions across the span and through the domain are given in section 3. Different values of the efficiency, loss coefficient, or dissipation coefficient can be specified for different quasi-orthogonal calculating stations. A value on the first quasi-orthogonal is always needed. This value remains constant until changed by the next quasi-orthogonal at which the loss is defined. If only a single value is specified across the span then this is applied on the mean streamline and each streamline has the same entropy rise as on the mean streamline. If a calculation with a constant efficiency for all streamlines is required then the efficiency needs to be specified constant on at least two points across the span.

•

If i_loss = 2 then built-in loss correlations are used according to the values given in sections 3 and 4.

Determines the method for calculation of a blade outlet flow angle (deviation or slip). Notes: •

102

If i_dev = 0 , the flow follows the mean blade camber line given in the .geo file with no deviation. This option allows a mean S2 though-flow calculation to be carried

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Screen Output Files (screen.scn) Parameter

Description out using the mean stream surface obtained from a series of S1 blade-to-blade calculations, provided that these are then given as the geometry of the camber surface in the .geo file. Note that, in order to retain similar structures for the correlations file, the lines described in sections 5 and 6 are still needed but have no effect. •

If i_dev = 1 then data is specified in sections 5 and 6 to predict the variation of the flow angle at the blade outlet from the mean blade camber line across the span. The information can be either in the form of a deviation angle, a specified flow outlet angle, a specified slip factor, or a modification to the cosine rule, according to the type of blade row.

•

If i_dev = 2 then inbuilt correlations are used to determine the flow angle according to the type of blade row as specified in sections 5 and 6.

Determines the blockage correlation for boundary layers that is to be used (ewb means “end-wall blockage”)

i_ewb

Notes: •

If i_ewb = 0 then no end-wall blockage is applied. Note that, in order to retain similar structures for the correlations file, the lines described in sections 7 and 8 are still needed, but have no effect.

•

If i_ewb = 1 then data is specified in sections 7 and 8 to predict the variation of the flow blockage for each quasiorthogonal and for each streamline. A single value implies that a constant blockage value is applied in the whole calculation domain.

•

If i_ewb = 2 then builtin correlations are used to determine the blockage according to the type of blade row as specified in sections 7 and 8.

Section 3: Loss input data locations The syntax is: n_loss_sl

n_loss_qo

or n_loss_bladerow

n_dummy

If i_loss equals 0 or 1 then the losses for each quasi-orthogonal can be specified, and the following values are required: Parameter

Description

n_loss_sl

Number of the spanwise positions for which the loss data is supplied. Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF Parameter

Description

n_loss_qo

Number of quasi-orthogonal calculating stations through the domain on which the loss information is specified.

If i_loss equals 2 then the losses for each blade row can be specified, and the following values are required: Parameter

Description

n_loss_bladerowNumber of separate blade rows for which the loss data is supplied. A dummy integer value to ensure that line 3 always has two integer values.

n_dummy

If i_loss equals 0 or 1 then the following version of section 4 is required: Section 4: User-defined loss data specification (n_loss_qo * n_loss_sl lines) This version of section 4 is applicable when i_loss equals 0 or 1. The syntax is: i_qo_loss

k_loss

f_loss

loss

Parameter

Description

i_qo_loss

Number of the quasi-orthogonal calculating station on which the loss, deviation, and blockage information is specified. The specified values will be applied for all blade rows and calculating stations downstream of this quasi-orthogonal until the value is changed by a subsequent section 4 with a new value of j_qo_loss. The first value of i_qo_loss must be 1. Subsequent lines may change the way in which the losses are defined.

k_loss

Parameter to define how the losses are specified. The value of the polytropic efficiency, the loss coefficient, or the dissipation coefficient, determines the entropy increase depending on the values of k_loss. Notes:

104

•

If k_loss = 1 then the small-scale static to static polytropic efficiency (etapoly) is specified. This is used in such a way that the entropy always increases so that, for an accelerating flow with a decrease in static enthalpy, it defines a turbine efficiency, and for a decelerating flow, it defines a compressor efficiency. This small-scale efficiency is applied in blade rows and in ducts.

•

If k_loss = 2 then the entropy loss coefficient (xsi) is specified. Note that the loss coefficient is the entropy loss coefficient with respect to outlet plane dynamic head for accelerating blade rows (turbine rotors and stators) and with respect to the inlet plane dynamic head for decelerating blade rows (compressor rotors and stators). An inlet guide vane for a compressor is therefore calculated as a

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Screen Output Files (screen.scn) Parameter

Description turbine blade row, and an outlet guide vane for a turbine as a compressor blade row. Like the deviation, this value is only used at the trailing edge of a blade row. •

If k_loss = 3 then the dissipation loss coefficient (cd) is specified. This is applied in blade rows and in ducts.

•

If k_loss = 4 to 9 then various forms of efficiency are used to specify the rotor blade row losses, as follows: k_loss = 4 total-total polytropic efficiency k_loss = 5 total-static polytropic efficiency k_loss = 6 static-static polytropic efficiency k_loss = 7 total-total isentropic efficiency k_loss = 8 total-static isentropic efficiency k_loss = 9 static-static isentropic efficiency These are applied in blade rows only. The full range is allowed, but options 6 and 9 are probably not very relevant.

•

If k_loss = 10 then the loss in a stator vane can be specified as a total pressure loss coefficient.

•

If k_loss = 11 then the performance of a stator van can be specified as a static pressure rise coefficient.

Note These options have been programmed in such a way that different blade rows may have different values of k_loss. f_loss

The fraction of the span at which the value of loss applies. If only a single value is given, it is applied at the mean streamline independent of the value of f_loss.

loss

Depending on the value of k_loss, this is interpreted as a small-scale polytropic efficiency (etapol), a loss coefficient (xsi) or a dissipation coefficient (cd).

If i_loss equals 2 then the following version of section 4 is required: Section 4: Correlation-based loss data specification (n_loss_bladerow lines) This version of section 4 is applicable when i_loss equals 2. The syntax (of a single line) is: i_loss_bladerow

i_loss_type

factor1

factor2

factor3

factor4

factor5

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factor6

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Vista TF Parameter

Description

i_loss_bladerowNumber of the blade row on which the loss information is specified. The specified values will be applied for all blade rows downstream of this blade row until the value is changed by a subsequent section 4 with a new value of i_loss_bladerow, and then this will again be applied until changed. The first value must be 1. Parameter to define which correlations are used for the blade row losses. The current loss correlations incorporated into the method are as follows:

i_loss_type

•

i_loss_type = 1 Turbine loss correlations of Kacker and Okapuu

•

i_loss_type = 2 Turbine loss correlations of Dunham and Came

•

i_loss_type = 11 Compressor loss correlations of Miller and Wright

factor1 to factor6

User-defined multiplication or addition factors to the losses determined by the correlations. This allows the loss correlations to be modified to improve matching with experimental or CFD data. These have different functions for the different correlation systems. factor1: Multiplication factor on profile losses factor2: Multiplication factor on secondary losses factor3: Multiplication factor on tip clearance losses factor4: Multiplication of penetration of secondary losses factor5: Multiplication of penetration of tip clearance losses factor6: Not in use

Section 5: Deviation input data locations The syntax is: n_dev_sl n_dev_qo

or n_dev_bladerow n_dummy

If i_dev equals 0 or 1 then the deviation for each quasi-orthogonal can be specified, and the following values are required:

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Screen Output Files (screen.scn) Parameter

Description

n_dev_sl

Number of spanwise positions for which the flow angle data is supplied.

n_dev_qo

Number of quasi-orthogonal calculating stations on which the flow angle information is specified.

If i_dev equals 2 then the deviation flow angle data can be specified for each blade row, and the following values are required: Parameter

Description

n_dev_bladerow Number of separate blade rows for which the flow angle data is supplied. A dummy integer value to ensure that section 5 always has two integer values.

n_dummy

If i_dev equals 0 or 1 then the following version of section 6 is required: Section 6: Flow angle data specification (n_dev_qo * n_dev_sl lines) This version of section 6 is applicable when i_dev equals 0 or 1. The syntax is: i_qo_dev

k_dev

f_dev

dev

Parameter

Description

i_qo_dev

Number of the quasi-orthogonal calculating station on which the deviation information is specified. The specified values will be applied for all blade row trailing edges downstream of this quasi-orthogonal until the value is changed by a subsequent section 6 with a new value of i_qo_dev. The first value must be 1.

k_dev

Determines the type of outlet flow angle calculation, as follows: •

If k_dev = 1 then the deviation angle is specified (in degrees).

•

If k_dev = 2 then the relative outlet flow angle is specified (in degrees).

•

If k_dev = 3 then a slip factor is specified and applied on the mean line (dimensionless). Note that if no value is specified then the Wiesner slip factor is used. Only recommended for radial impellers and not for mixed flow stages, which should use deviation.

•

If k_dev = 4 then a slip factor is applied at each radius of the trailing edge (dimensionless). Note that if no value is specified then the Wiesner slip factor is used. Only recommended for radial impellers and not for mixed flow stages, which should use deviation.

•

If k_dev = 5 then a correction to the flow angle calculated by the cosine rule is specified. If zero is specified for

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Vista TF Parameter

Description this correction, then the cosine rule is used to calculate the relative flow angle at the outlet for all radii. If a nonzero value is specified then this modifies the flow angle by this constant amount (in degrees). A positive value increases the deviation.

f_dev

The fraction of the span of at which the value of the deviation (and similar things) applies. If only a single value is given, it is applied at the mean streamline independent of its value.

dev

Depending on the value of k_dev, this is interpreted as a deviation angle, flow angle, slip factor, or correction to the cosine rule.

If i_dev equals 2 then the deviation for each blade row must be specified using the following version of section 6: Section 6: Flow angle data specification (n_dev_bladerow lines) This version of section 6 is applicable when i_dev equals 2. The syntax is: i_bladerow_dev

Parameter

i_dev_type

factor1

factor2

factor3

factor4

factor5

Description

i_bladerow_dev Number of the blade row on which the deviation information is specified. The specified values will be applied for all blade row trailing edges downstream of this quasi-orthogonal until the value is changed by a subsequent section 6 with a new value of i_bladerow_dev. The first value must be 1. i_dev_type

Parameter to define which correlations are used for the blade row deviations. The current deviation correlations incorporated into the method are as follows: •

i_dev_type = 1 (Kacker Okapuu) Turbine deviation using the cosine rule.

•

i_dev_type = 2 (Dunham and Came) Turbine deviation using the cosine rule.

•

i_dev_type = 11 (Miller Wright) Compressor deviation correlations of Miller and Wright.

factor1 to factor6

User-defined multiplication or addition factors to the deviations determined by the correlations. This allows the deviation correlations to be modified to improve matching with experimental or CFD data. These have different functions for the different correlation systems. factor1: Additive factor in degrees (°) on hub deviation factor2: Additive factor in degrees (°) on mean deviation

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factor6

Screen Output Files (screen.scn) Parameter

Description factor3: Additive factor in degrees (°) on tip deviation factor4: Not in use factor5: Not in use factor6: Not in use

Section 7: Blockage input data locations The syntax is: n_ewb_sl

n_ewb_qo

or n_ewb_bladerow

n_dummy

If i_ewb equals 0 or 1 then the blockage for each quasi-orthogonal can be specified, and the following values are required: Parameter

Description

n_ewb_sl

Number of spanwise positions for which the blockage data is supplied.

n_ewb_qo

Number of quasi-orthogonal calculating stations on which the blockage information is specified.

If i_ewb equals 2 then the blockage correlation can be specified for each blade row, and the following values are required: Parameter

Description

n_ewb_bladerow Number of separate blade rows for which the blockage is supplied. A dummy integer value to ensure that section 7 always has two integer values.

n_dummy

If i_ewb equals 0 or 1 then the blockage for each quasi-orthogonal must be specified using the following version of section 8: Section 8: End wall blockage data specification (n_dev_qo * n_dev_sl lines) This version of section 8 is applicable when i_ewb equals 0 or 1. The syntax is: i_qo_ewb

k_ewb

f_ewb

ewb

Parameter

Description

i_qo_ewb

Number of the quasi-orthogonal calculating station on which the blockage information is specified. The specified values will be applied for all blade rows and calculating stations downstream of this quasi-orthogonal until the value is

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109

Vista TF Parameter

Description changed by a subsequent section 4 with a new value of j_qo_ewb. The first value must be 1.

k_ewb

Determines the type of blockage calculation. Has no effect because the blockage is input in only one form as below.

f_ewb

The spanwise location of the value of the blockage. If only a single value is given, it is applied at all streamlines.

ewb

End-wall boundary layer blockage is specified. A value of 0.05 represents 5% blockage of the flow channel by the end-wall boundary layers. If zero is specified then there is no end-wall boundary layer blockage. Typically a constant value is specified across the whole span, but this parameter can be varied across the span to allow for the higher blockage in the endwalls related to blade ends with tip clearance.

If i_ewb equals 2 then the following version of section 8 is required: Section 8: End wall blockage data specification (n_dev_qo * n_dev_sl lines) This version of section 8 is applicable when i_ewb equals 2. The syntax is: i_bladerow_ewb

Parameter

i_ewb_type

factor1

factor2

factor3

factor4

factor5

Description

i_bladerow_ewb Number of the blade row on which the blockage information is specified. The specified values will be applied for all blade row trailing edges downstream of this quasi-orthogonal until the value is changed by a subsequent section 6 with a new value of i_bladerow_ewb. The first value must be 1. i_ewb_type

Parameter to define which correlations are used for the bladerow blockage. The current blockage correlations incorporated into the method are as follows: •

i_ewb_type = 1 No blockage consistent with Kacker Okapuu.

•

i_ewb_type = 2 No blockage consistent with Dunham and Came.

•

i_ewb_type = 11 Compressor blockage correlations of Miller and Wright.

factor1 to factor6

User-defined multiplication or addition factors to the blockage determined by the correlations. This allows the end-wall blockage correlations to be modified to improve matching with experimental or CFD data. These have different functions for the different correlation systems. factor1: Not in use factor2: Not in use

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factor6

Screen Output Files (screen.scn) Parameter

Description factor3: Not in use factor4: Not in use factor5: Not in use factor6: Not in use

Specification of the Output Data File (*.out) The output data file includes lines of text in ASCII format that show the results of the simulation. The file consists of several sections: Section 1: Input data At the start of this file, a list of the input data files that were used is recorded in this file so that a record of the file names is available. INPUT DATA FILES:

OUTPUT DATA FILES:

Control data file: agard.con Geometric data file: agard.geo Aerodynamic data file: agard.aer Correlation data file: agard.cor Restart data file: agard.rst Results file: agard.out Tecplot data file: impeller.txt CFD-POST data file: agard.csv Convergence history file: agard.hst Interface output file: agard.int

Section 2: Reference data The program uses the input data to set up the values of various other parameters; for example, where the reference mass flow is specified, the reference volume flow is calculated. The values of all other parameters not included in the input specification are given in this section. In addition, the internal calculation of the damping factors is provided. Other data listed here relates to the program's own estimates of the throat area and the throat position. An example is given below. Example radial compressor calculation: Reference flow parameters ------------------------Mass flow distribution across streamlines: 0.000 0.062 0.125 0.188 0.250 0.312 0.375 0.438 0.500 0.562 0.625 0.688 0.750 0.812 0.875 0.938 1.000 Inlet distribution across streamlines: Fraction of flow: 0.00 Total pressure: 100000.00 Total temperature: 293.00 Inlet swirl: 0.00 Ideal gas calculation gamma_gas gas_m r_gas cp_gas 1.400 3.500 287.200 1005.200 ref_pt(bar) ref_tt ref_rhot ref_soundt 1.0000 293.00 1.1884 343.23 Reference rotational direction: clockwise ref_d ref_u ref_omega ref_n 0.2700 398.10 2948.91 28160.0

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111

Vista TF ref_mach ref_phi ref_mass ref_volume 1.1599 0.0667 2.3000 1.94 ref_re ref_mue 6963614.0 0.00001834 ref_n1 ref_n2 ref_n3 28160.0 0.0 0.0 Simulation with no spanwise mixing Iterate to mass flow, ref_mass =

2.30000

First approximation of streamline positions taken from an earlier calculation Estimated max. thicknesses for blade row 1 span 0.00000 0.17343 0.34429 0.51305 0.67879 0.84126 0.97669 1.00000 thickne 0.00351 0.00319 0.00291 0.00266 0.00241 0.00215 0.00195 0.00191 User-input throat widths for blade row 1 span 0.00000 0.17343 0.34429 0.51305 0.67879 0.84126 0.97669 1.00000 throat 0.01760 0.02137 0.02460 0.02732 0.02959 0.03141 0.03257 0.03276 Estimated throat positions for blade row 1 span 0.00000 0.17343 0.34429 0.51305 0.67879 0.84126 0.97669 1.00000 throat_pos 0.00969 0.02084 0.03424 0.04835 0.06224 0.07573 0.08688 0.08882 Empirical correlation data User specified losses User specified deviation No blockage specified Relaxation factor calculation of Wilkinson -----------------------------------------Maximum aspect ratio: at calculating station: damp_sc (user input): damp_sc (Wilkinson):

6.0667 5 0.2500 0.0577

Warning: damp_sc reduced by the code to the value suggested by Wilkinson

Section 3: Short history of the convergence The .out file contains a statement about convergence of the results. A converged calculation includes a header such as the following: *********************************************** * Vista TF converged -it_main: 6 * * * * cm_error(%) p_error(%) mass_error(%) * * 0.042 0.000 0.000 * *********************************************** * Global performance * * * * mass (kg/s): 0.093200 * * est. choke: 0.107995 * * t-t t-s s-s * * eta_p: 0.8453 0.7415 * * eta_s: 0.8553 0.7583 * * pr: 0.5800 0.5374 0.6100 * * er (1/pr): 1.7243 1.8609 1.6392 * * power (kW): -5.4316 * ***********************************************

A more detailed convergence history is output to the history file, which is described inSpecification of Convergence History Data File (*.hst) (p. 117).

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Screen Output Files (screen.scn) Section 4 : Simulation results on quasi-orthogonal planes and streamlines Results are provided at every quasi-orthogonal requested (see control file parameter i_print_plane) in the level of detail requested (parameter i_print_level). The data is provided across the span for each streamline. If the number of streamlines is greater than 9 then data for every second streamline is given. The structure of this data and the information provided varies depending on the type of calculation station. The example below is for a radial impeller leading edge: Quasi-orthogonal - i = 3 n_blade n_curve i_type i_row i_spool 13 6 3 0 0 Rotor blade - leading edge At throat (or just upstream of throat) Compressor Radial impeller Throat area = 0.00274713 Annulus choke parameters: dm_dcm = 0.79601 Mach_eff = 0.45166 choke mass at this q_o = 7.72100 choke_mass of machine = 7.72100 choke_mass of this blade row = 7.72100 current_mass at this q_o = 6.70000 inlet mass flow = 6.70000 Factor on slope of ree: grad_re = 1.00000 cm_guess_save = 152.57564 Flow parameters - print_level=1 streamline 1 3 5 7 9 11 13 15 17 r [m] 0.07612 0.08753 0.09759 0.10647 0.11445 0.12176 0.12855 0.13493 0.14100 z [m] -0.13500-0.13500-0.13500-0.13500-0.13500-0.13500-0.13500-0.13500-0.13500 1/rc[1/m] -5.996 1.353 2.758 2.818 2.475 1.984 1.438 0.864 0.244 throat mm 23.00 24.41 25.66 26.77 27.40 27.84 28.17 28.30 29.00 f_sl [-] 0.17503 0.17777 0.18110 0.18431 0.18734 0.19021 0.19295 0.19556 0.19806 f_qo [-] 0.00000 0.17593 0.33098 0.46775 0.59076 0.70340 0.80807 0.90652 1.00000 f_bl [-] 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 f_thr [-] 0.02584 0.03400 0.04157 0.04823 0.05408 0.05923 0.06379 0.06785 0.07150 gamma_in 1.00000 1.00000 1.00000 1.00000 1.00000 1.00000 1.00000 1.00000 1.00000 gamma_out 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 cm [m/s] 146.87 142.25 145.30 149.18 152.57 155.22 157.11 158.32 158.87 - error % 0.0001 -0.0002 0.0001 0.0001 0.0001 0.0001 0.0000 -0.0002 -0.0001 - max 169.57 166.48 168.30 172.19 174.87 177.33 179.61 180.96 186.11 cu [m/s] 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 M_cm [-] 0.437 0.423 0.432 0.444 0.455 0.463 0.469 0.472 0.474 M_crit[-] 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 M_rel [-] 0.765 0.837 0.914 0.985 1.050 1.109 1.163 1.213 1.260 beta_fl° -55.19 -59.65 -61.79 -63.21 -64.34 -65.33 -66.23 -67.08 -67.90 beta_bl° -43.03 -46.77 -50.17 -52.99 -55.37 -57.46 -59.30 -60.92 -62.35 incidence 12.16 12.88 11.62 10.22 8.98 7.86 6.93 6.16 5.55 p [bar] 0.8706 0.8778 0.8730 0.8669 0.8614 0.8571 0.8540 0.8519 0.8510 t [K] 282.38 283.04 282.60 282.04 281.54 281.14 280.84 280.66 280.57 rho[kg/m3] 1.0742 1.0806 1.0764 1.0710 1.0661 1.0623 1.0595 1.0577 1.0569 A*/A 0.9485 0.9758 0.9935 0.9998 0.9980 0.9907 0.9799 0.9666 0.9517 m/m_max 0.8661 0.8545 0.8633 0.8664 0.8725 0.8753 0.8747 0.8749 0.8536 m_prime 75.46 84.55 95.91 106.88 116.97 126.15 134.46 141.98 148.76 m_pr_max 87.12 98.94 111.09 123.37 134.07 144.11 153.70 162.27 174.26 ch_ratio 0.8662 0.8545 0.8634 0.8664 0.8725 0.8753 0.8748 0.8749 0.8537 Flow parameters - print_level=2 eps [°] 12.82 14.30 12.54 10.34 8.13 6.01 4.00 2.08 0.23 psi [°] 77.18 75.70 77.46 79.66 81.87 83.99 86.00 87.92 89.77 c [m/s] 146.87 142.25 145.30 149.18 152.57 155.22 157.11 158.32 158.87 w [m/s] 257.28 281.50 307.34 330.98 352.35 371.83 389.80 406.55 422.31 u [m/s] 211.24 242.91 270.83 295.46 317.60 337.88 356.73 374.45 391.29 wu [m/s] -211.24 -242.91 -270.83 -295.46 -317.60 -337.88 -356.73 -374.45 -391.29 M_abs [-] 0.437 0.423 0.432 0.444 0.455 0.463 0.469 0.472 0.474 alpha_fl° 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 pt [bar] 0.9921 0.9921 0.9921 0.9921 0.9921 0.9921 0.9921 0.9921 0.9921 tt [K] 293.00 293.00 293.00 293.00 293.00 293.00 293.00 293.00 293.00 s [J/kgK] 2.29 2.29 2.29 2.29 2.29 2.29 2.29 2.29 2.29 ds[J/kgK] 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 ewb [-] 0.0500 0.0500 0.0500 0.0500 0.0500 0.0500 0.0500 0.0500 0.0500 Loading parameters - print_level=3 w_s [m/s] 287.34 314.82 342.24 366.60 388.17 407.50 425.12 441.51 456.87 w_p [m/s] 227.21 248.18 272.45 295.36 316.53 336.16 354.47 371.59 387.74 M_ws [-] 0.855 0.936 1.018 1.091 1.157 1.215 1.268 1.318 1.364

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Vista TF M_wp [-] C_btob [-]

0.676 0.234

0.738 0.237

0.810 0.227

0.879 0.215

0.943 0.203

1.002 0.192

1.058 0.181

1.109 0.172

1.157 0.164

Specification of the Text Data Files (*.txt) The text data files include lines of text in ASCII format which are intended as input for various software packages for producing plots of the converged results. The text files can be used as input data for Tecplot. Standard layout (.lay) files for Tecplot have been prepared which allow typical diagrams to be produced on the basis of this data. The information is structured in such a way that it can just as easily be used by Excel or some other similar program with an appropriate interface. In fact, after running the program, several standard .txt files for Tecplot are produced: one covering the whole flow field and one for each blade row. The flow field data is written in the file prefix.txt, and the blade-row data in the files row_01_prefix.txt, row_02_prefix.txt, and so on, whereby the number of the files refers to the blade rows numbered from the start of the computational domain. You only need to provide the name of one of these files in the vista_tf.fil file, because the others are automatically generated and numbered by the program. Some standard Tecplot layout files have been prepared that operate on the .txt files to produce typical plots that are needed during the design of a component. For example, the files used for radial compressor impellers are called: flowfield_2d_v_2_0.lay and rc_impeller_row1.lay. The first of these prepares a plot showing the 2D meridional channel with contours of constant parameters (such as meridional velocity, swirl velocity, static temperature, Mach number, cm_error and so on) and the second prepares blade loading plots for a typical blade row. The layout file (.lay) determines the format of the plot and the ASCII .txt file contains the data to be plotted. The format and the scales can also be changed on-line within Tecplot by clicking on the screen. Other Layout files for other cases (ac = axial compressor, hp = hydraulic pump, ht= hydraulic turbine, rt = radial turbine, at= axial turbine) are also available and these can be easily customized (scales, parameters and so on). The standard Tecplot layout files (.lay) have all been written to work on the data in text files named impeller.txt and row_01_impeller.txt, and so on. The first dataset, impeller.txt, contains information for the contour plots showing the meridional velocity and other parameters projected on the meridional plane and the second, row_01_impeller.txt, contains the various blade loading parameters for an individual blade row. If the case concerned has several blade rows then there is also a file called row_02_impeller.txt, row_03_impeller.txt, and so on; there is one file for each blade row. A new layout file is needed for each blade row. The letters “impeller” in this name rely on the fact that the prefix for the .txt file has this name in the vista_tf.fil file. Other prefixes will produce .txt files containing the prefix as specified in the vista_tf.fil file. In this case, the layout files need to be modified; the layout files can be opened in a text editor; the name of the .txt file is on the second line. This name can then be changed to match the name given as a prefix in the vista_tf.fil file. Alternatively, the same layout files can be used for several cases if all data that needs to be plotted always retains the prefix name impeller; the text output file from vista_tf always has the name impeller.txt in the vista_tf.fil file. Generally, a good strategy is to set up the .aero, .cor, .con, and .txt files with a certain prefix in the vista_tf file and to let these keep the same names for all runs on a particular case because they normally do not change as the design progresses. It then remains necessary to switch the .geo files around to look at different impellers, or else the prefix for the .geo file can be retained and the cases can be distinguished by simply putting them into different directories to distinguish the different cases. The data in the prefix.txt file is in approximately the following format: TITLE Flow field data for whole flow field from hub to shroud for all q-os

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Screen Output Files (screen.scn)

Variables = '"r" "z" "cm" "cu" "cr" "cz" "p" "t" "pt" "tt" "s" "h" "q_o" "error" "choke_ratio" "M_rel" "M_abs" "alpha_flow" "beta_flow" "1/rc" "beta"' "r" "z" "cm" "cu" "cr" "cz" "p" "t" "pt" "tt" "s" "h" “q_o” “error” "choke_ratio" "M_rel" "M_abs" "alpha_flow" "beta_flow" "1/rc" "beta”

Radius coordinate Axial coordinate Meridional velocity Swirl velocity Radial velocity Axial velocity Static pressure Static temperature Total pressure Total temperature Entropy Static enthalpy an integer identifying the particular type of q-o Meridional velocity error in % choke ratio (ratio of local mass flow to choke flow at this location) Relative Mach number Absolute Mach number Absolute flow angle [°] Relative flow angle [°] Curvature ( inverse of the radium of curvature) Blade angle [°]

The data in the row_01_prefix.txt file is approximately in the following format: TITLE Data on hub, mean and tip streamlines for all blade rows from LE to TE and data along leading edge and trailing edge of all blade rows VARIABLES =VARIABLES = "i_type", "f_bl", "M", "M_s", "M_p", "w", "w_s", "w_p",... "p", "p_s", "p_p", "c_btob", "c_htos", "beta_bl", "beta_fl", "dep_angle", "gamma_in", ... gamma_out", "f_qo", "de_haller", "cp_ideal", "incidence", "deviation", "lambda", ... "df_lieblein", "zweifel" "c_lift", "c_zw" "f_bl" Fraction of meridional distance along the blade "M" Mean mid-passage Mach number (relative to blade) "M_s" Suction side Mach number "M_p" Pressure side Mach number "w" Mean mid-passage velocity (relative to blade) "w_s" Suction surface velocity "w_p" Pressure surface velocity "p" Static pressure in mid-channel between two blades "p_s" Suction surface static pressure "p_p" Pressure surface static pressure "c_btob" Blade to blade loading parameter (c_btob = (w_s-w_p)/w, that is the difference between suction surface and pressure surface velocities divided by the mid-channel velocity "c_htos" Hub to shroud loading parameter (c_htos = (cm_shroud – cm_hub)/ cm_mean, that is the difference between the meridional velocity on the casing and the hub divided by the mean velocity. "beta_bl" Blade angle in degrees [°] "beta_fl" Flow angle in degrees [°] "dep_angle" Departure angle in degrees [°] "gamma_in" Blending functon at blade inlet "gamma_out" Blending function at blade outlet "f_qo" fractional distance along q-o "de_haller" De Haller number (de_haller = w2/w1, that is outlet/ inlet relative velocity "cp_ideal" Ideal static pressure recovery coefficient ( Cpideal = 1 – (de_haller)**2 ) "incidence" Incidence at the leading edge [°] "deviation" Deviation at the trailing edge[°] "lambda" Work coefficient ( lambda = (h2-h1)/u**2, that is Deltah / u squared) "df_lieblein" Lieblein Diffusion Factor (see below) "zweifel" Zweifel loading parameter (see below) "c_lift" Lift coefficient (see below) "c_zw" Lift coefficient times solidity (see below)

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Vista TF Note that the values of the last four parameters have been included mainly for axial blade rows. Each of them includes the blade solidity (ratio of chord to spacing) in its definition. In radial machines, the spacing and solidity change with radius along the streamline. There is no generally agreed method to calculate these parameters for radial machines, so the mean value of the spacing has been selected in the following definitions used in Vista TF. In any case, caution is suggested in the use of these parameters for radial machine blade rows because the experimental basis for limit values has generally been derived from axial machines. Lieblein diffusion factor (df_lieblein)

Zweifel coefficient (zw)

Lift coefficient (CL)

where Zwiefel number (c_zw)

Specification of the CFD-Post Output Files (*.csv) The text data files *prefix.csv include lines of text in ASCII Comma Separated Variable format files (.csv) which are intended as input for CFD-Post for plotting purposes, using the user surface data format. For details of this format, see the documentation provided with CFD-Post. In the current .csv files, the following data is available for each grid node: [Name] Vista-TF [Data] X [m], Y [m], Z [m], Cm [m/s], Cu [m/s], Cr [m/s], Cz [m/s], p [bar], t [K], s [J kg^-1 K^-1], h [J/kg], q_o [], error [], M_rel[], M_abs[], rc [m^-1]

The file global_prefix.csv contains a list of parameters, whereby these are specified as: Name 1 = value1 [units] Name 2 = value2 [units]

Separated by comment lines which begin with “#”. In addition, there are four additional files produced for each blade row from 1 to n: row_0n_hub_prefix.csv row_0n_mean_prefix.csv row_0n_tip_prefix.csv row_0n_loading_prefix.csv

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Screen Output Files (screen.scn) These contain essentially similar information to the row_0n_prefix.txt files described above, but this is split into four separate files: one for the hub, one for the mean span, one for the tip, and one for the loading parameters.

Specification of Convergence History Data File (*.hst) The convergence history data file includes lines of text in ASCII format that show the convergence of the simulation. This contains details of the convergence of the main iterative procedures, and extensive details of the terms in the radial equilibrium equation for each stream tube and calculating plane. It is rare for this to be examined in any depth, but this can be useful to identify problems if the solution fails to converge. Section1: Input Data At the start of the .hst file, the input data is recorded. This is essentially in the same format as the input files. At the start of this file, there is a list of the names of the input data files that were used. This information can be useful if an error occurs in the input data because the .hst file records only the data that has been successfully read into the program. Section 2: Convergence Data At every iteration, a summary of the iteration progress is provided. It looks like this: History of the main iteration loop ---------------------------------it_main: 1 error_cm(%): 100.000 at i_qo: 0 j_sl: 0 it_mass: 11 at i_qo: 1 it_main: 2 error_cm(%): 38.940 at i_qo:10 j_sl:17 it_mass: 11 at i_qo: 1 it_main: 3 error_cm(%): 30.036 at i_qo:10 j_sl:17 it_mass: 11 at i_qo: 3 it_main: 4 error_cm(%): 24.600 at i_qo:10 j_sl:17 it_mass: 11 at i_qo: 4 it_main: 5 error_cm(%): 20.939 at i_qo:10 j_sl:17 it_mass: 11 at i_qo: 5 it_main: 6 error_cm(%): 18.306 at i_qo:10 j_sl:17 it_mass: 11 at i_qo: 6 it_main: 7 error_cm(%): 16.403 at i_qo:10 j_sl:17 it_mass: 11 at i_qo: 6 ..... it_main: it_main: it_main: it_main: it_main:

284 285 286 287 288

error_cm(%): error_cm(%): error_cm(%): error_cm(%): error_cm(%):

0.013 0.012 0.011 0.010 0.009

at at at at at

i_qo: i_qo: i_qo: i_qo: i_qo:

7 7 7 7 7

j_sl:17 j_sl:17 j_sl:17 j_sl:17 j_sl:17

it_mass: it_mass: it_mass: it_mass: it_mass:

1 1 1 1 1

at at at at at

i_qo: i_qo: i_qo: i_qo: i_qo:

1 1 1 1 1

Section 3: Streamline Curvature Solution Data At every quasi-orthogonal, details of the terms in the radial equilibrium equation for each stream tube are provided. This can be useful in identifying errors and also helpful to determine the magnitude of the terms in the equations. “rhs” is the value of the right hand side of the radial equilibrium equation, giving the square of the gradient of the meridional velocity. The streamline curvature solution data looks like this: Quasi-othogonal - i = 5 n_blade n_curve i_type i_row i_spool 9 8 3 0 0 Radial equilibrium parameters -print_level = 4 rhs 1049.90 1059.86 871.10 684.48 510.68 349.39 199.63 55.28 ret 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 ret_dh 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 ret_tds 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 ret_drcu 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 sct 1049.90 1059.86 871.10 684.48 510.68 349.39 199.63 55.28 sct_rc 641.48 681.97 558.43 431.70 315.91 211.42 118.25 34.87 sct_dcm 408.43 377.89 312.67 252.78 194.78 137.97 81.38 20.40 bft 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dft 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 cm_error% -0.0010 0.0002 -0.0003 -0.0007 -0.0007 -0.0003 0.0003 0.0010 f_mixing 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1/rc 2.853 4.466 4.153 3.505 2.773 2.016 1.261 0.517 -0.209 cm 137.936 145.590 152.396 157.708 161.716 164.594 166.473 167.450 167.568 rcu 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF drcu/dm s bl_block

47.323 53.336 48.562 35.419 15.376 -11.226 -43.868 -81.313-123.649 1.885 1.885 1.885 1.885 1.885 1.885 1.885 1.885 1.885 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

Software Limitations There are several potential sources of errors and uncertainties in all CFD simulations, all of which are extremely relevant in turbomachinery applications using a throughflow program, such as Vista TF. The standard categorization of such errors is into the following groups: •

Numerical errors

•

Model errors

•

Application uncertainties

•

User errors

•

Software errors

and these are briefly described next. Numerical errors decrease the quality of simulations and can be reduced but not eliminated. The control of numerical error is largely a matter of adequate grid design, appropriate numerical discretization, and adequate level of convergence. An example in Vista TF is the approximation of the streamlines by a piecewise parabola through 3 points. In a throughflow calculation the so-called model errors probably outweigh all other sources of error. These are related to the fact that the equations that are solved do not really describe the real flow particularly adequately (in this case the solution is for inviscid, circumferentially-averaged mean values on widely spaced grid lines). Application uncertainties may be only partly in your control and are related to the detail with which aspects of the geometry are accurately known or specified. Typical examples would be a lack of knowledge about the fillet radii in the geometry for a blade row calculation, or not having correct information about the inlet boundary conditions for a specific calculation. User errors relate to incorrect use of the program, such as making use of incorrect control parameters to control the calculation. With regard to software errors, every reasonable precaution to ensure the accuracy and reliability of the Vista TF program has been taken. However, when using the program, especially for a critical design, you should first complete an appropriate validation and calibration process. A good turbomachinery analysis procedure dictates that any program, including Vista TF, must be thoroughly tested with non-critical data before there is any reliance on it.

Streamline Curvature Throughflow Theory Vista TF is a general purpose streamline curvature throughflow program for the analysis of all types of turbomachinery, but with special emphasis on single stage centrifugal machines, such as radial pumps, turbines, and compressors, which can usually not be calculated by other throughflow programs. The program has the ability to compute radial blade rows in both compressors and turbines, and the swirling flows in the radial channels of such machines. This is possible because the blade and channel geometry is defined in a very general way independent of the meridional streamline direction. This section of the documentation is intended for readers who are not familiar with throughflow methods; it provides a general introduction to the streamline curvature axisymmetric meridional throughflow calculation method. Some details are given in Casey and Robinson (2008) [5] (p. 125). This section includes a list of technical papers on the subject. The following topics are discussed: The Equations The Mean Stream Surface 118

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Streamline Curvature Throughflow Theory The Grid Ductflow and Throughflow Iterative Solution Procedure Initial Estimate Radial Equilibrium Equation Combination of Velocity Gradient and Continuity Equations Relaxation Factors Streamline curvature Equations for Enthalpy and Angular Momentum Boundary Conditions Empirical Data Blade-to-blade Solution Spanwise Mixing Streamline Curvature Throughflow Theory: Bibliography

The Equations The equations that are solved are: •

The continuity equation

•

The energy equation (Euler equation of turbomachinery)

•

A suitable equation of state

•

The inviscid momentum equation for the flow on the mean axisymmetric stream surface

Although these equations are inviscid and do not include frictional forces, the effect of the losses are included by empirical changes to the entropy in the equation of state, such that the final solution has a density and pressure field consistent with the presence of losses in the flow.

The Mean Stream Surface This blade-like surface may be regarded as being obtained by averaging all flow properties in the circumferential direction, or as being the flow on a mean stream surface between the blade rows, whose orientation is roughly determined by the blade camber surface. The flow blockage caused by the blades is roughly fixed by the circumferential blade thickness of the blades. It is often known as the S2 meridional stream surface, in contrast to the S1 blade-to-blade surface, and in fact corresponds to the so-called S2m surface in the theory of Wu (1952) [22] (p. 126). See Figure : S1 and S2 Stream Surfaces in the Theory of Wu (1952) (p. 120). Note that it has an arbitrary orientation in the circumferential direction and that the flow in the mean stream surface is determined by the slope angles of the surface to the axial and the radial directions, both of which need to be specified in the geometrical input data.

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Figure: S1 and S2 Stream Surfaces in the Theory of Wu (1952)

The Grid The grid for the calculation is based on the streamlines of the mean circumferentially averaged flow in the meridional direction, and fixed calculating stations which are roughly normal to the streamlines. The meridional streamline grid is not fixed, apart from the hub and shroud streamlines on the annulus walls, but changes continually during the iterations so that location of the final streamlines is a result of the solution The fixed calculating stations are orientated with the blade row leading and trailing edges and are often known as quasi-orthogonals because they are normally nearly orthogonal to the streamlines. The quasi-orthogonals can be in duct regions, that is in the blade-free space upstream and downstream of blade rows, at the leading and trailing edges of the blade rows (which actually are also generally considered to be in the duct region) and internally within the blade rows. See Figure : Quasi-orthogonal Calculating Stations in an Axial Compressor Stage Calculation (p. 121). The computational results are available only at the points where the streamlines cross the quasi-orthogonals. In comparison with modern CFD methods, a very crude grid is used with typically 9 to 17 streamlines and 3 to 15 quasi-orthogonals per blade row, giving 50 to 300 nodes per blade row in comparison to 100 000 to 500 000 in modern CFD simulations.

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Streamline Curvature Throughflow Theory

Figure: Quasi-orthogonal Calculating Stations in an Axial Compressor Stage Calculation

In many early streamline curvature programs, the quasi-orthogonals were generally straight radial lines from hub to casing placed roughly at the location of the leading and trailing edges, but given the more extensive use of lean and sweep in modern designs, and the natural leading edge and trailing edge curvature arising from the variable stagger across the span in most rotors, curved quasi-orthogonals of arbitrary orientation are more appropriate. The use of a grid involving meridional streamlines, all of which proceed smoothly from the inlet plane to the outlet plane of the calculation domain, assumes that there is no reverse flow, and thus operation points with reverse flow in the mean meridional flow (even at the design point) cannot be calculated by this method.

Ductflow and Throughflow Earlier methods, which did not include blade internal calculating planes, are often known as duct flow methods because only planes in the duct regions between the blades, and at the leading and trailing edges, are used. Throughflow refers to methods in which internal planes within each blade row are included as shown in Figure : Quasi-orthogonal Calculating Stations in an Axial Compressor Stage Calculation (p. 121). In throughflow methods, the component of the blade force acting along the direction of the quasi-orthogonal can be included in the meridional throughflow equations, so that some global aspects of the effect of the blade lean on the meridional flow can be included. This is not possible in duct flow methods without some empirical adjustment of the pressure gradients.

Iterative Solution Procedure The solution method is iterative in terms of several variables (primarily the meridional velocity, but also the density, streamline location, and other variables), all of which progressively converge to a final converged solution within a fairly complex structure of three nested iterations. In this convergence procedure, many variables lag behind the main iteration for changes in the meridional velocity, so that during one iteration leading to an update of the meridional velocity, many parameters are treated as constant and are then updated based on the new estimate of the meridional velocity prior to the next iteration. It is assumed that this has no effect on the solution provided that a converged solution for all variables is reached. Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Initial Estimate The initial solution generally comprises a first guess of streamline positions (typically by dividing the flow path into equal areas at each quasi-orthogonal) and flow variables at all the grid points (that is, the junction points between the variable streamlines and the fixed quasi-orthogonals). This is then successively refined as a result of each iteration. Once a first estimate of the streamline positions is in place then various terms in the radial equilibrium equation, such as the curvature of the streamlines or the rate of change of meridional velocity along the streamlines, can be determined.

Radial Equilibrium Equation The momentum equation on the mean stream surface is a form of the radial equilibrium equation, giving a velocity gradient equation for the gradient of the meridional velocity along a calculating station, or quasiorthogonal:

This equation is given in many text books (see Cumpsty (1989) [6] (p. 125)) and is not repeated here. It relates the velocity gradient to the shape and the current positions of the streamlines, to the orientation of the mean stream surface, and to the flow parameters and their gradients from the previous iteration. In its simplest form, this equation is the well-known simple radial equilibrium equation of turbomachinery flows, which gives the relationship between the radial gradient of the axial velocity and the gradient of the swirl in the radial direction, as follows:

In its general form the radial equilibrium equation takes into account flow gradients, streamline curvature, and radial flows, and allows a general arbitrary orientation of the quasi-orthogonal lines. The key difference between the simple radial equilibrium equation and the more general equation is the inclusion of the streamline curvature terms, and it is these terms that give their name to the method. There are several forms of this velocity gradient equation, but the one used here follows the method of Denton (1978) [7] (p. 125), but takes into account the blade force terms as described in chapter 3.4 of the book by Cumpsty (1989) [6] (p. 125).

Combination of Velocity Gradient and Continuity Equations The velocity gradient equation is solved in combination with a method for finding the correct velocity level on the mean streamline that ensures that the velocity along the quasi-orthogonal satisfies the continuity equation giving the correct mass flow across the quasi-orthogonal. See Figure : Continuity and the Velocity Gradient Used in Determining the Meridional Velocity Level (p. 123). The meridional velocity on the mean streamline is specified in the innermost iteration, integrated across the flow channel with the help of the meridional velocity gradient, and then continually updated until the mass flow is correct. This requires some care to ensure that the method converges for all mass flows up to the choking mass flow. In this iteration, the density is also needed in the continuity equation. In fact there are two values of the density that can be used, corresponding to supersonic or subsonic flow. In this method, no attempt is made to distinguish these during the innermost iteration; the density is simply taken as constant at the value from the previous iteration, and automatically takes on the supersonic or subsonic value as the iteration converges.

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Streamline Curvature Throughflow Theory

Figure: Continuity and the Velocity Gradient Used in Determining the Meridional Velocity Level

Relaxation Factors The meridional velocity distribution along the quasi-orthogonal determines the spacing of the streamlines of the meridional flow, and hence the meridional streamline positions. These positions are continually updated as the program converges. Generally, it is not acceptable to use the newly calculated positions of the streamlines directly from one iteration to the next, but a damping factor (often much less than unity) is required to factor the streamline shifts to obtain convergence. A big weakness of streamline curvature methods is that the required damping factor becomes very small when the quasi-orthogonal lines are closely spaced, and so improved accuracy through more calculating planes causes a large increase in calculating time. For this reason, a relatively coarse grid (compared to CFD computations) is used, leading to calculations that take just a few seconds on a modern PC. The problem with closely spaced quasi-orthogonals is related to the large errors in the estimated streamline curvature when a small error in the streamline position is present. It is for this reason that many methods do not include blade internal calculation stations because these automatically decrease the spacing between adjacent quasi-orthogonals.

Streamline curvature The streamline positions can be used to interpolate new blade element data appropriate to their current location and to find the slopes, curvatures, and derivatives of the flow parameters along the streamlines. This data is needed in the radial equilibrium equation (velocity gradient equation; see Radial Equilibrium Equation (p. 122)). The accuracy and stability of streamline curvature methods is related to the prediction of the curvatures of the streamlines. Several different numerical methods for this have been examined. In the current method, the curvatures are calculated with a parabolic approximation through three adjacent points along the streamline.

Equations for Enthalpy and Angular Momentum In the region between blade rows, the total enthalpy and angular momentum may be considered to be convected along the meridional streamlines from the previous station. The entropy is also convected but rises due to the additional losses between the calculating stations. In a blade row, the changes in momentum and enthalpy are calculated from the Euler equation on the assumption that the flow follows the mean stream surface. The mean blade stream surface is roughly orientated in alignment with the camber surface of the blade, but methods are needed for finding the true fluid flow direction taking into account the incidence and deviation of the flow from the mean blade surface. This is generally dealt with using empirical correlations for outlet angle, deviation, or slip factor.

Boundary Conditions At the inlet plane (first quasi-orthogonal) you are generally required to specify the variation of total pressure, total temperature, and angular momentum or flow angle, together with the gas data and information on Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF the mass flow at the outlet plane. For calculations with choked flows, it is not possible to calculate with the mass flow, making it necessary to calculate with specified outlet static pressure, such that the mass flow is a result of the simulation.

Empirical Data Additional empirical methods are used to provide data for the loss production, for the boundary layer blockage, and for the deviation of the flow direction from the mean blade camber surface, so that the effect of viscosity can be taken into account. In fact Denton (1978) [7] (p. 125) argues that “in many applications, throughflow calculations are little more than vehicles for inclusion of empiricism in the form of loss, deviation and blockage correlations, and their accuracy is determined by the accuracy of the correlations rather than the numerics”. The three main effects of the empirical data are: •

In the equation of state, a change in the entropy leads to a pressure loss for a given value of the total enthalpy.

•

In the continuity equation, the blockage due to the boundary layer displacement effect leads to a higher value of the meridional velocity.

•

In the momentum equation, the deviation of the flow from the blade direction leads to a change in the calculated swirl velocity.

Thus, although the basic inviscid equation of motion used by the method is inherently incapable of predicting entropy rises through the machine, some effects of losses can be included. There are numerous possible combinations of data for the empirical information, based on various definitions of loss coefficients, dissipation coefficients, efficiencies, and so on, and this leads to the largest source of confusion in the data preparation for throughflow programs, and a large and complex array of branching “IF” statements within a typical throughflow program to deal with the alternatives. In making this program, a single form of loss definition has been included based on the entropy rise.

Blade-to-blade Solution The mean stream surface provides the flow field in the meridional plane through the turbomachine. Generally the engineer also needs information on the blade surface velocity and Mach number distributions, so the meridional solution needs to be combined with a blade-to-blade method to find blade surface velocities. This may be either a simple approximation or a more accurate solution of the blade-to-blade flow equations. The more accurate methods enable the exact location of the mean stream surface of the flow to be determined at different blade-to-blade planes, so this can also lead to a further iteration in which the mean stream surface is no longer considered as fixed. Such iterative solutions are often known as S1/S2 solutions (the S1 surface being the blade-to-blade surface and the S2 surface being the meridional surface. See Figure : S1 and S2 Stream Surfaces in the Theory of Wu (1952) (p. 120)). This technique has generally been replaced these days by fully 3D CFD solutions with mixing planes, but is still of historical interest. The simpler methods generally use a linear approximation for the velocity variation from suction surface to pressure surface. These can be expected to produce sensible results only when a sufficient number of internal blade row calculating stations are included in the grid, probably 5 as the minimum.

Spanwise Mixing A major shortcoming of the basic streamline curvature method is the neglect of the spanwise transport of angular momentum, energy, and losses in the direction normal to the streamlines. By definition, a throughflow program is based on the assumption that the flow remains in concentric streamtubes as it passes through the turbomachine, and no mass transfer occurs across the meridional streamlines which are the streamtube boundaries. In a duct region of a throughflow calculation, enthalpy, angular momentum (swirl), and entropy are taken to be conserved along the meridional streamlines. In reality, there are several

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Streamline Curvature Throughflow Theory mechanisms that lead to an apparent spanwise transport of fluid relative to flow on the mean streamlines, as follows: •

Non-axisymmetric blade-to-blade stream surfaces as a result of streamwise vorticity being shed by the blades (stream-surface twist)

•

Secondary flows in the end-wall boundary layers and in the blade boundary layers

•

Wake momentum transport downstream of blade rows

•

Tip clearance flows with tip clearance vortices

•

Turbulent diffusion

As a result of not modeling these effects, throughflow programs in which realistic loss levels are specified for the end-wall regions often predict unrealistic profiles of the loss distribution after several stages because there is no mechanism for the high losses generated near the end walls to be mixed out. The simplest approach to deal with this problem is to specify unrealistic loss distributions across the span that avoid high levels in the end walls. In fact, in preliminary design calculations, this is often adequate. A useful approximation is to specify a mean-line value of loss coefficient or efficiency and to assume that the entropy generated by the losses is the same on each stream-tube. This approximates a complete mixing of the entropy distribution across the span. Several more sophisticated methods to include more detailed physics of these mixing processes have been attempted so that realistic loss distributions can be specified. The common approach is to model the spanwise mixing as turbulent diffusion, even though some of the effects are due to deterministic flow features. Even with throughflow programs in which spanwise mixing is incorporated, it is still generally not possible to fully incorporate the very high loss levels close to the end walls. Vista TF includes these effects as turbulent diffusion across the streamlines.

Streamline Curvature Throughflow Theory: Bibliography [1] G. G. Adkins and L. H. Smith. “Spanwise mixing in axial flow turbomachines”. Trans ASME Journal of Engineering for Power , Vol. 104. pg. 97-110. 1982. [2] P. M. Came. “Streamline curvature throughflow analysis”. Proc. First European Turbomachinery Conference, VDI Berichte 1185. pg. 291. 1995. [3] M. V. Casey and O. Hugentobler. “The prediction of the performance of an axial compressor stage with variable stagger stator vanes”. VDI Berichte Nr. 706. pg. 213-227. 1988. [4] M. V. Casey and P. Roth. “A streamline curvature throughflow method for radial turbocompressors”. I. Mech. E. Conference C57/84. 1984. [5] M. V. Casey and C. J. Robinson. “A new streamline curvature throughflow code for radial turbomachinery”. ASME TURBOEXPO 2008, ASME GT2008-50187. Berlin. 2008. [6] N. A. Cumpsty. Compressor aerodynamics. Longman Scientific. New York. 1989. [7] J. D. Denton. “Throughflow calculations for axial flow turbines”. Trans ASME, Journal of Engineering for Power, Vol 100. 1978. [8] J. D. Denton and C. Hirsch. “Throughflow calculations in axial tubomachines”. AGARD Advisory Report No. 175 AGARD-AR-175. 1981.

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Vista TF [9] S. J. Gallimore. “Spanwise mixing in multistage axial flow compressors: part II throughflow calculations including mixing”. Trans. ASME, Journal of turbomachinery, Vol. 108. pg. 10-16. 1986. [10] I. K. Jennions and P. Stow. “The quasi-three-dimensional turbomachinery blade design system, Part I: Throughflow analysis, Part II: Computerized system”. Transactions of the ASME, Journal of Engineering for Gas Turbines and Power Vol. 107. pg. 308-16. 1985. [11] I. K. Jennions and P. Stow. “The importance of circumferential non-uniformities in a passage averaged quasithree-dimensional turbomachinery design system”. Transactions of the ASME, Journal of Engineering for Gas Turbines and Power Vol. 108. pg. 240-5. 1986. [12] K. I. Lewis. “Spanwise transport in axial-flow turbines: Part 2 - Throughflow calculations including spanwise mixing”. Trans. ASME, Journal of turbomachinery, Vol. 116. pg. 187-193. 1984. [13] B. Liu, S. Chen, and H. F. Martin. “A primary variable throughflow code and its application to last stage reverse flow in LP steam turbine”. Paper: IJPGC2000-15010, Proc. Int. Joint Power Generation Conference, July 23-26. Miami Beach, Florida. 2000. [14] H. Marsh. “A digital computer program for the through-flow fluid mechanics in an arbitrary turbomachine using a matrix method”. Aeronautical Research Council R and M 3509. 1968. [15] C. Hirsch and J. D. Denton. “Throughflow calculations in axial turbomachines”. AGARD Advisory report No. 175, AGARD-AR-175. 1981. [16] K. I. Lewis. “Spanwise transport in axial flow turbines: part 2 - throughflow calculations including spanwise transport”. Trans. of ASME, Journal of Turbomachinery, Vol. 116. pg. 187-193. 1994. [17] R. A. Novak. “Streamline curvature computing procedures for fluid flow problems”. Trans. of ASME, Journal of Engineering for power, Vol 89. pg. 478-490. 1967. [18] M. Schobeiri. Turbomachinery Flow Physics and Dynamic Performance. Springer. Berlin. 2005. [19] L. H. Smith. “The radial equilibrium equation of turbomachinery”. Trans. ASME Journal of Engineering for Power, Vol 88. pg. 1-12. 1966. [20] D. H. Wilkinson. “Streamline curvature methods for calculating the flow in turbomachines”. Report No W/M(3F). English Electric. Whetstone, England. pg. 1591. 1969. [21] D. H. Wilkinson. “Stability, convergence, and accuracy of two-dimensional streamline curvature methods using quasi-orthogonals”. paper 35, I.Mech.E. Convention. Glasgow. 1970. [22] C. H. Wu. “A general theory of three-dimensional flow in subsonic, and supersonic turbomachines of axial, radial and mixed-flow types”. Trans. ASME, Nov. 1952. pg. 1363-1380. 1952. [23] C. C. Yeoh and J. B. Young. “Non-equilibrium throughflow analyses of low-pressure, wet steam turbines”. ASME J. Eng. for Gas Turbines & Power, Vol 106. pg. 716-724. 1984.

Appendices The following appendix topics are available: Appendix A: A Note on Sign Convention for Angles and Velocities Appendix B: Example of a Control Data File (*.con) Appendix C: Example of a Geometry Data File (*.geo) for a Radial Impeller 126

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Appendices Appendix D: Example of an Aerodynamic Data File (*.aer) Appendix E: Examples of Correlations Data Files (*.cor) Appendix F: Troubleshooting Appendix G: The RTZTtoGEO Program

Appendix A: A Note on Sign Convention for Angles and Velocities When looking along the axis of the machine in the direction of flow we have a cylindrical coordinate system (r, theta, z) (or (r, θ , z)) . The angular coordinate (theta) is taken as positive in the clockwise direction and negative in the anti-clockwise direction. The normal case considered by Vista TF is clockwise rotation when looking along the axis in the direction of the flow so that the angular coordinate increases in the rotational direction. See Figure : Coordinate System used by Vista TF (p. 127) below.

Figure: Coordinate System used by Vista TF

The sign convention for velocity values is that an axial velocity component in the positive axial direction is positive, a radial component in the positive radial direction is positive, and a circumferential component in the positive angular direction (direction of rotation) is positive. Blade lean angles are then defined from the axial and radial directions in a similar way using the rotational direction as a basis. As you move along an axial rotor blade in the axial direction of a clockwise rotating machine then the blade angle theta steadily decreases as the blade is sloped backwards against the rotational direction (radial impeller outlet angles are generally also backswept). In a stator vane the angular coordinate increases as you step along the blade in the meridional direction. The rate of change of the angular coordinate with the meridional direction then defines the sign of the blade angle, and this applies for the blade angles, flow angles and also applies to the blade lean angles. See below. For example, in an axial compressor rotor where the blades lean back from the direction of rotation, theta becomes more negative as you move along the blade from the leading edge (LE) to the trailing edge (TE). In a compressor stator, theta becomes more positive as you move along the blade. This rule works for axial, radial, and mixed flow compressors, provided the meridional direction is used as a basis. In a turbine stator Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF theta also increases positively from LE to TE and, in a turbine rotor, theta decreases from LE to TE. There are some exceptions to this rule, related to high camber at leading edges to adapt the flow to the incoming flow direction.

Note Vista TF uses the rules outlined above to identify the type of machine from the geometrical data of the blade angles in the geometry input file, so you do not have to specify this.

Definition of Blade Lean Angles Consider a point q on a radial impeller blade camber surface, as shown in Figure : Definition of Angles (p. 128). We can define the blade lean angles, and as the angle made by the blade fibers with a radial line and the angle made with an axial line, as follows:

Figure: Definition of Angles

Notes on

:

•

This is the blade lean to the radial direction.

•

This angle is zero for a blade comprising purely radial blade elements, so is generally close to zero for axial blade rotor rows (which tend to have no lean) and centrifugal impeller leading edges or radial turbine trailing edges.

•

It is non-zero for blades with lean. If, when moving along the blade in the radial direction, the lean is against the direction of rotation then it is negative and lean in the direction of rotation is positive.

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Appendices •

A radial compressor impeller with a purely radial blade at impeller outlet (no backsweep) would have =0° and

corresponds to the back-sweep angle in a typical back-swept radial impeller. For an

would be negative (-30°) at the trailing edge. Note that, in some impeller with 30° of back-sweep, sign conventions, the back-sweep angle would be given a positive value, but in Vista TF, it is negative. •

In a the diffuser of a radial pump or compressor stage, this angle corresponds to the diffuser blade angle and would be typically between 60° and 70° at the leading edge, and would decrease through the blade row.

Notes on

:

•

This is the blade angle measured from the axial direction in the direction of rotation.

•

In an axial blade element (or close to the leading edge of a typical radial impeller or the trailing edge of a radial turbine impeller), this is the blade camber angle. At the inlet to an axial blade row, this is the blade inlet angle; at the outlet, it is the blade outlet angle.

•

In a typical rotor blade, it is negative and, in a typical stator, it is positive. Note that the common exceptions would be turbine rotors with a low degree of reaction and compressor rotor roots with very high turning.

•

In a compressor where the flow is turned by the blade rows towards the axial direction, the absolute values decrease from the leading edge to the trailing edge whereas in a turbine where more swirl is added to the flow, the absolute values increase from the leading edge to the trailing edge.

•

For a blade with purely axial blade elements (as in a typical 2D diffuser and at a radial impeller outlet with no rake angle), this angle is zero.

Definition of Meridional Streamline Inclination Angle or Pitch Angle The angle

is the inclination of a meridional streamline to the axial direction:

which on the hub and casing walls becomes the meridional slope angle of the walls.

Definition of Blade Angle Internally the program uses the angles from the meridional direction.

Notes on •

and

to calculate

, which is the effective blade angle measured

is defined as:

:

The wrap angle is taken as positive in the direction of rotation. This is consistent with the flow angle definition used by the program. Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF •

This angle is zero for a blade in which the wrap angle does not change in the meridional direction, such as an axial strut in an axial channel or a radial strut in a radial channel, where

.

•

If the wrap angle increases in the meridional direction then the blade angle is positive. If the wrap angle decreases in the meridional direction then the blade angle is negative.

•

Note that the actual value of the blade angle as seen by the flow is dependent on the lean angle of the meridional streamline, and is not an absolute fixed value for a certain blade. Thus a change in the meridional direction of the flow at an impeller outlet with lean changes the value of the blade angle.

Appendix B: Example of a Control Data File (*.con) The following is a described example of a control data file: Three lines to identify the run (maximum 72 characters per line): PCA stage Control parameters for typical radial impeller 5 May 2008

Two lines for the integer control parameters: n_sl max_it_main max_it_mass 9 500 10

Two lines for integer control parameters for output data and the use of the restart file: i_print_plane i_print_level i_print_units i_display i_restart i_interface 4 5 0 0 0 0

Two lines for integer control parameters for various models and reference parameters: i_expert i_flow i_fluid i_inbc i_mass i_mix i_ree 0 1 0 0 0 0 0

Two lines for convergence and damping factors: damp_sc damp_vl cm_start tolerance_cm tolerance_mass grad_ree 0.25 0.25 0.2 0.01 0.005 1.00

Appendix C: Example of a Geometry Data File (*.geo) for a Radial Impeller The following is a described example of a geometry data file: Three lines to identify the run: PCA Stage from .rtzt file Thickness converted to tangential thickness 10 blades and 1 splitter

Two lines for the number of quasi-orthogonal lines: n_qo scale 23 1.00000

A section that defines the quasi-orthogonal type and end points: i 1 2 3 4 5

r_hub 0.00069 0.00224 0.00702 0.01189 0.01357

130

r_shr 0.05594 0.05215 0.04941 0.04776 0.04720

z_hub -0.04959 -0.03682 -0.02481 -0.01284 -0.00004

z_shr n_blade n_curve i_type -0.04959 0 1 1 -0.03757 0 1 1 -0.02527 0 1 1 -0.01277 0 1 1 -0.00018 10 5 3

i_row 0 0 0 0 0

i_spool 0 0 0 0 0

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Appendices 6 0.01447 7 0.01609 8 0.01832 9 0.02108 10 0.02463 11 0.02867 12 0.03314 13 0.03799 14 0.04318 15 0.04866 16 0.05440 17 0.06035 18 0.06646 19 0.07271 20 0.07902 21 0.08033 22 0.08164 23 0.08295

0.04728 0.04758 0.04809 0.04884 0.04993 0.05132 0.05305 0.05513 0.05759 0.06040 0.06358 0.06709 0.07087 0.07488 0.07901 0.08032 0.08164 0.08295

0.00570 0.01128 0.01664 0.02175 0.02700 0.03188 0.03637 0.04045 0.04408 0.04726 0.04995 0.05214 0.05379 0.05485 0.05538 0.05544 0.05548 0.05550

0.00371 0.00759 0.01145 0.01526 0.01930 0.02325 0.02706 0.03068 0.03407 0.03717 0.03988 0.04216 0.04393 0.04514 0.04575 0.04585 0.04592 0.04597

10 10 10 20 20 20 20 20 20 20 20 20 20 20 20 0 0 0

5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 1 1 1

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 1 1 1

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

A section that defines the quasi-orthogonals and the blade geometry: i j r_qo theta_qo z_qo thu_qo gamma_r_qo gamma_z_qo 5 1 0.01357 0.32039 -0.00004 0.00255 -0.18038 -23.15654 5 2 0.02198 0.26684 -0.00008 0.00244 -0.36249 -32.52025 5 3 0.03038 0.21411 -0.00015 0.00251 -0.34266 -41.27189 5 4 0.03879 0.26814 -0.00016 0.00243 -0.00979 -49.73230 5 5 0.04720 0.29630 -0.00018 0.00234 -0.18913 -57.43224 6 1 0.01447 -9.69106 0.00570 0.00269 1.88713 -23.08947 6 2 0.02267 -8.14852 0.00518 0.00256 0.41685 -31.31698 6 3 0.03087 -7.40827 0.00464 0.00243 -0.99339 -39.39957 6 4 0.03908 -6.96808 0.00417 0.00230 -2.04619 -47.44992 6 5 0.04728 -6.75726 0.00371 0.00218 -3.95792 -54.90281 7 1 0.01609 -18.29413 0.01128 0.00262 3.70754 -22.85821 7 2 0.02396 -15.68568 0.01033 0.00248 1.15036 -30.47241 7 3 0.03183 -14.35239 0.00936 0.00234 -1.75718 -37.83696 7 4 0.03970 -13.58089 0.00846 0.00220 -3.70752 -45.35764 7 5 0.04758 -13.16589 0.00759 0.00206 -6.69381 -52.39817 8 1 0.01832 -25.28463 0.01664 0.00254 4.70103 -22.81646 8 2 0.02576 -22.28703 0.01531 0.00241 1.41759 -29.88146 8 3 0.03320 -20.61659 0.01398 0.00227 -2.35690 -36.52612 8 4 0.04065 -19.60303 0.01270 0.00212 -5.03581 -43.43454 8 5 0.04809 -18.99898 0.01145 0.00196 -8.73336 -50.00039 9 1 0.02108 -30.92988 0.02175 0.00248 4.74907 -23.14610 9 2 0.02802 -28.02047 0.02011 0.00234 1.11611 -29.56330 9 3 0.03496 -26.23881 0.01846 0.00220 -2.97754 -35.52497 9 4 0.04190 -25.07781 0.01685 0.00204 -6.21556 -41.74088 9 5 0.04884 -24.32487 0.01526 0.00188 -10.40615 -47.79160 10 1 0.02463 -36.00322 0.02700 0.00242 3.85677 -23.97254 10 2 0.03096 -33.42982 0.02507 0.00228 0.15779 -29.56658 10 3 0.03728 -31.67995 0.02313 0.00213 -3.84908 -34.83600 10 4 0.04361 -30.43321 0.02121 0.00197 -7.49971 -40.24432 10 5 0.04993 -29.55790 0.01930 0.00182 -12.07824 -45.67586 11 1 0.02867 -40.35207 0.03188 0.00236 2.23718 -25.26450 11 2 0.03435 -38.17139 0.02974 0.00222 -1.42539 -29.89481 11 3 0.04001 -36.55263 0.02757 0.00207 -5.15749 -34.49204 11 4 0.04567 -35.29039 0.02542 0.00192 -8.89269 -39.12102 11 5 0.05132 -34.35094 0.02325 0.00177 -13.85353 -43.85841 12 1 0.03314 -44.26280 0.03637 0.00232 0.10221 -26.97474 12 2 0.03816 -42.42247 0.03407 0.00217 -3.48507 -30.56208 12 3 0.04314 -40.96080 0.03175 0.00203 -6.83731 -34.52932 12 4 0.04811 -39.72235 0.02942 0.00188 -10.45941 -38.40800 12 5 0.05305 -38.76700 0.02706 0.00173 -15.90754 -42.28558 13 1 0.03799 -47.91006 0.04045 0.00228 -2.40966 -29.07832 13 2 0.04233 -46.32055 0.03805 0.00214 -5.94640 -31.56104 13 3 0.04663 -45.00031 0.03562 0.00200 -8.93117 -34.88947 13 4 0.05090 -43.80060 0.03317 0.00185 -12.32638 -38.07380 13 5 0.05513 -42.85755 0.03068 0.00171 -18.25871 -40.88997 14 1 0.04318 -51.39712 0.04408 0.00226 -5.26535 -31.52634 14 2 0.04685 -49.96856 0.04163 0.00212 -8.83099 -32.82496 14 3 0.05047 -48.75090 0.03914 0.00198 -11.46588 -35.54585 14 4 0.05405 -47.58476 0.03663 0.00184 -14.51275 -38.15374 14 5 0.05759 -46.66554 0.03407 0.00170 -20.92644 -39.61549 Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF 15 15 15 15 15 16 16 16 16 16 17 17 17 17 17 18 18 18 18 18 19 19 19 19 19 20 20 20 20 20

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5

0.04866 0.05168 0.05464 0.05755 0.06040 0.05440 0.05678 0.05910 0.06137 0.06358 0.06035 0.06211 0.06382 0.06548 0.06709 0.06646 0.06763 0.06875 0.06983 0.07087 0.07271 0.07330 0.07384 0.07437 0.07488 0.07902 0.07904 0.07902 0.07901 0.07901

-54.78108 -53.43857 -52.27642 -51.13094 -50.22395 -58.09399 -56.77929 -55.62589 -54.47843 -53.55910 -61.35160 -60.02598 -58.83913 -57.66538 -56.69062 -64.56377 -63.20368 -61.94636 -60.72039 -59.63480 -67.72621 -66.32376 -64.96857 -63.66663 -62.40934 -70.87669 -69.41995 -67.94505 -66.52396 -65.01019

0.04726 0.04478 0.04227 0.03975 0.03717 0.04995 0.04747 0.04497 0.04245 0.03988 0.05214 0.04967 0.04719 0.04469 0.04216 0.05379 0.05134 0.04888 0.04641 0.04393 0.05485 0.05243 0.05000 0.04757 0.04514 0.05538 0.05297 0.05056 0.04815 0.04575

0.00224 0.00211 0.00197 0.00184 0.00170 0.00224 0.00211 0.00198 0.00185 0.00172 0.00227 0.00214 0.00201 0.00188 0.00175 0.00231 0.00220 0.00207 0.00195 0.00181 0.00241 0.00231 0.00218 0.00202 0.00194 0.00263 0.00260 0.00239 0.00205 0.00216

-8.53323 -34.20149 -12.12520 -34.30999 -14.44340 -36.45351 -17.13253 -38.55727 -23.67359 -38.40397 -12.36035 -36.91306 -15.80725 -36.02020 -17.90732 -37.55025 -20.39385 -39.11425 -26.48486 -37.37148 -16.87176 -39.31440 -19.92706 -37.88099 -21.91242 -38.69098 -24.33144 -39.57177 -29.09953 -36.76047 -22.10267 -40.96566 -24.62539 -39.61601 -26.48127 -39.65304 -28.81198 -39.70950 -31.57298 -37.06592 -27.77629 -41.34374 -29.91973 -40.62141 -31.51785 -40.06106 -33.54181 -39.54783 -34.26011 -38.72800 -32.69635 -39.92279 -34.43144 -39.83097 -36.32393 -39.91470 -37.25527 -39.78318 -37.35707 -41.84796

A section for additional geometry data: j 1 2 3 4 5

throat throat_pos clearance max_thick 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000

te_thick dummy1 dummy2 dummy3 0.00000 0.00 0.00 0.00 0.00000 0.00 0.00 0.00 0.00000 0.00 0.00 0.00 0.00000 0.00 0.00 0.00 0.00000 0.00 0.00 0.00

Appendix D: Example of an Aerodynamic Data File (*.aer) The following is a described example of an aerodynamic data file: Three lines to identify the aerodynamic data: Radial stage at design flow ideal gas 5 May 2008

Two lines for the reference aerodynamic parameters, which depend on the value of i_flow in the .con file. Assuming i_flow = 1: ref_n 60000.0

ref_mass 1.00

ref_d 0.15804

Two lines for the Reynolds number: Re_ref 0.0

Two lines for the fluid data, which depends on the value of i_fluid in the .con file. Assuming i_fluid = 1 (for ideal gas): cp_gas 1005.2

gamma_gas 1.40

Two lines for the number of points on the inlet boundary where flow conditions are specified: 132

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Appendices n_inbc 1

Lines for the fraction of the inlet boundary where flow conditions are specified (n_inbc values): f_inbc 0.0

Lines for the pressure on the inlet boundary (n_inbc values, which depend on i_bc in the .con file). Assuming i_bc = 0: pt_inbc 98000.0

Lines for the temperature on the inlet boundary (n_inbc values, which depend on i_bc in the .con file). Assuming i_bc = 0: tt_inbc 293.0

Lines for swirl on the inlet boundary (n_inbc values, which depend on i_bc in the .con file). Assuming i_bc = 0: rcu_inbc 0.00

Two lines for the mixing model and blade transparency model parameters: eddy 0.0001

f_bl_le f_bl_te 0.0 0.0

Appendix E: Examples of Correlations Data Files (*.cor) EXAMPLE 1 The following example of a correlations data file is for a radial compressor. For most radial compressor or pump impeller calculations, the only parameter that changes is the small-scale polytropic efficiency. Note that a single value of the empirical information for flow outlet angle is specified (k_dev = 3 implies the use of a slip factor, and because k_dev is specified as 0.0 the program calculates the slip factor from the Wiesner correlation). Three lines to identify the run (maximum 72 characters per line): Typical correlations file for radial compressor small-scale efficiency, slip factor of 0.0 (so Wiesner) and no blockage 5 May 2008

Two lines for integer data: i_loss i_dev i_ewb 1 1 0

Two lines for loss input data: n_loss_sl n_loss_qo 1 1

Two lines for empirical loss data: i_qo_loss k_loss f_loss loss 1 1 0.500 0.86

Two lines for deviation input data: Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF n_dev_sl n_dev_qo 1 1

Two lines for empirical deviation data: i_qo_dev k_dev f_dev dev 1 3 0.500 0.00

Two lines for blockage input data: n_ewb_sl n_ewb_qo 1 1

Two lines for empirical blockage data: i_qo_ewb k_ewb f_ewb ewb 1 1 0.500 0.00

EXAMPLE 2 The following example of a correlations data file is for a nine-stage radial compressor with a vaneless diffuser and a return channel downstream of each impeller except the ninth. The losses in this case are specified as a single polytropic efficiency for everything, and the blockage is zero. But for the deviation of the flow from the blade angle at the trailing edge it is sensible to use a slip factor of 100 for the impeller and a deviation angle for the stator vanes. In this case 0.0 is specified as the slip factor so the Wiesner slip factor is used, and 5.00° is specified for the return channel deviation angle. k_dev controls whether to use the slip factor or deviation, and i_qo specifies the calculating station at which the slip factor or deviation is applied. A sensible rule would be to make the value of i_qo equal to the number of the q-o at the trailing edge, but the program can accept any value between the previous trailing edge and the current one. If there is a vaned diffuser with a different deviation angle then an additional line with k_dev set to 1 would be needed between each impeller and return channel line. Three lines to identify the run (maximum 72 characters per line): Typical correlations file for multistage radial compressor Efficiency, slip factor in impeller, deviation in stators, no blockage 18 September 2008

Two lines for integer data: i_loss i_dev i_ewb 1 1 0

Two lines for loss input data: n_loss_sl n_loss_qo 1 1

Two lines for empirical loss data: i_qo_loss k_loss f_loss loss 1 1 0.500 0.80

Two lines for deviation input data: n_dev_sl n_dev_qo 1 17

Lines for empirical deviation data: i_qo_dev 1 3 45 1 65 3

134

k_dev f_dev dev 0.500 0.00 0.500 5.00 0.500 0.0

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Appendices 95 115 145 165 195 215 245 265 295 315 345 365 395 415

1 3 1 3 1 3 1 3 1 3 1 3 1 3

0.500 0.500 0.500 0.500 0.500 0.500 0.500 0.500 0.500 0.500 0.500 0.500 0.500 0.500

5.00 0.0 5.00 0.0 5.00 0.0 5.00 0.0 5.00 0.0 5.00 0.0 5.00 0.0

Two lines for blockage input data: n_ewb_sl n_ewb_qo 1 1

Two lines for empirical blockage data: i_qo_ewb k_ewb f_ewb ewb 1 1 0.500 0.00

EXAMPLE 3 The following example of a correlations data file is for a radial turbine stage with an inlet nozzle and an impeller. In the example shown, the losses are different for the two components. The deviation angle is specified by use of the cosine rule for both components (k_dev = 5) but a correction to this (2.00°) is applied in the rotor. Three lines to identify the run (maximum 72 characters per line): Typical correlations file for radial turbine stage Efficiency, deviation as mod to cosine rule and no blockage 18 September 2008

Two lines for integer data: i_loss i_dev i_ewb 1 1 0

Two lines for loss input data: n_loss_sl n_loss_qo 1 2

Three lines for empirical loss data: i_qo_loss k_loss f_loss loss 1 1 0.500 0.88 35 1 0.500 0.75

Two lines for deviation input data: n_dev_sl n_dev_qo 1 2

Lines for empirical deviation data: i_qo_dev k_dev f_dev dev 1 5 0.500 0.00 35 5 0.500 2.00

Two lines for blockage input data: Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF n_ewb_sl n_ewb_qo 1 1

Two lines for empirical blockage data: i_qo_ewb k_ewb f_ewb ewb 1 1 0.500 0.00

EXAMPLE 4 In all of the above examples, a constant value of the empirical information is applied on all streamlines, so only a single value is specified. An additional feature is that the program also allows this data to vary across the span for each blade row. Then there would be an additional line for each fraction of the span. This is shown with regard to the losses, which specifies the efficiency at 0%, 25%, 50%, 75% and 100% of the span. Three lines to identify the run (maximum 72 characters per line): Radial compressor impeller with spanwise variation of eta Efficiency, slip factor for impeller with no blockage 18 September 2008

Two lines for integer data: i_loss i_dev i_ewb 1 1 0

Two lines for loss input data: n_loss_sl n_loss_qo 5 1

Lines for empirical loss data: i_qo_loss k_loss f_loss loss 1 1 0.000 0.77 1 1 0.250 0.79 1 1 0.500 0.80 1 1 0.750 0.79 1 1 1.000 0.77

Two lines for deviation input data: n_dev_sl n_dev_qo 1 1

Lines for empirical deviation data: i_qo_dev k_dev f_dev dev 1 3 0.500 0.00

Two lines for blockage input data: n_ewb_sl n_ewb_qo 1 1

Two lines for empirical blockage data: i_qo_ewb k_ewb f_ewb ewb 1 1 0.500 0.00

EXAMPLE 5 The following example of a correlations data file shows the use of a blade oriented specification for the Kacker Okapuu correlations for an axial turbine calculation. No blockage is specified.

136

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Appendices Three lines to identify the run (maximum 72 characters per line): Typical correlations file for axial turbine - no blockage Kacker-Okapuu 10 September 2008

Two lines for integer data: i_loss i_dev i_ewb 2 2 0

Two lines for loss input data: n_loss_bladerow dummy 1 1

Two lines for empirical deviation data (i_loss = 2): i_blrow i_loss_type f_loss(1) f_loss(2) f_loss(3) f_loss(4) f_loss(5) f_loss(6) 1 1 1.0 1.0 1.0 1.0 1.0 1.0

Two lines for deviation input data: n_dev_bladerow dummy 1 1

Lines for empirical deviation data: i_blrow i_dev_type f_dev(1) f_dev(2) f_dev(3) f_dev(4) f_dev(5) f_dev(6) 1 1 0.0 0.0 0.0 0.0 0.0 0.0

Two lines for blockage input data: n_ewb_sl n_ewb_qo 1 1

Two lines for empirical blockage data: i_qo k_ewb f_ewb ewb 1 1 0.500 0.00

EXAMPLE 6 The following example of a correlations data file shows the use of a blade oriented specification for the Miller-Wright correlations for an axial compressor calculation. Three lines to identify the run (maximum 72 characters per line): Typical correlations file for multistage axial compressor Miller Wright Correlations 10 September 2008

Two lines for integer data: i_loss i_dev i_ewb 2 2 2

Two lines for loss input data: n_loss_bladerow dummy 1 1

Two lines for empirical loss data (i_loss = 2): i_blrow i_loss_type f_loss(1) f_loss(2) f_loss(3) f_loss(4) f_loss(5) f_loss(6) 1 11 1.0 1.0 1.0 1.0 1.0 1.0

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Vista TF Two lines for deviation input data (i_dev = 2): n_dev_bladerow dummy 1 1

Lines for empirical deviation data (i_dev = 2): i_blrow i_dev_type f_dev(1) f_dev(2) f_dev(3) f_dev(4) f_dev(5) f_dev(6) 1 11 0.0 0.0 0.0 0.0 0.0 0.0

Two lines for blockage input data: n_ewb_bladerow dummy 1 1

Two lines for empirical blockage data: i_blrow i_ewb_type f_ewb(1) ... ... .... ... f_ewb(6) 1 11 1.0 1.0 1.0 1.0 1.0 1.0

Appendix F: Troubleshooting The Vista TF program and numerical method is extremely robust, especially in unchoked flows and when running from an existing restart file. There should generally be no numerical problems with radial compressor, radial turbine, and radial pump calculations, which are the first applications for which the program has been released. Nevertheless convergence problems and unexpected program errors can still occur. The most common problems are format errors in the input data or numerical problems inherent to the streamline curvature method or associated with choking. The numerical errors can sometimes result in a failure of the solution to converge or even a complete breakdown as the compiled program encounters a FORTRAN error, such as the square root of a negative number, or a floating point overflow. The most common of these are trapped and reported by the program. It is hoped that all such errors can be removed in a later version. The compiler of course will report these errors, but this is not of much use to the user. The most likely cause of such errors is a data error. The sections below outline typical problems and suggest solutions for these with some advice on how to deal with input format and data errors. If the solution converges to the user-specified level of convergence then the program exits normally with a value of 0 in the command line (CALL EXIT(0)). If the solution has not converged but the maximum number of iterations has been reached, then a value of 1 is returned. If the program has identified some serious difficulty which has an appropriate trap, then the program exits with a negative return value and prints an appropriate error message. Only the most common errors have been supplied with a trap against such errors. If the program identifies a feature of the input data which it determines may lead to some difficulties (rotational direction, grid aspect ratio, inconsistent flow and speed data) it prints a warning to the screen and the output file. This information may help to correct the data errors. Some examples of warnings and error messages are as follows: WARNING: Anti-clockwise rotation Vista TF suspects that the first rotor blade is counter-rotating Possible cures: (a) Change value of i_flow to be negative (b) Change geometry from left-handed to right-handed or vice versa

WARNING: Wilkinson damping factor used Damping factor damp_sc reduced by Vista TF to value suggested by Wilkinson WARNING: error increasing -relaxation factors reduced 5%

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Appendices

ERROR: Error noted in subroutine throughflow_manager ERROR TYPE: error_max > 400% ERROR PARAMETERS: -10 10 17 139 0 0 0.2100E+16 0.5600E+00 0.7250E+00 0.2905E+01 0.0000E+00 Problem: Near to choke on quasi-orthogonal: 17 on iteration: 139 Inlet mass flow: 0.56000 Local estimated choke mass flow: 0.72497 Local effective relative Mach number: 2.90494 Possible cures:

(a) Remove this q-o from domain (b) Check consistency of flow and speed

Input-output Errors If the program fails to run at all, then this is usually a sign that some of the formatted input data is not correct (no empty lines where these were expected, or an empty line where data was expected, or similar formatting problems). The screen monitor information then says that the file has broken down in a particular input subroutine; this provides a clue for identifying which file has an incorrect format. Most straightforward errors caused by new users or new cases are related to the data input files, which are fairly rigid with regards to the lines of data and which do not accept an empty line where a line of data should be. No built-in consistency checks of the input data are made, so errors of this nature can easily occur, especially at the beginning of a completely new calculation. To help avoid this type of error, you can copy lines from similar existing input files. The program might report the name of the input file that contains an error. Should such errors happen, you should examine the .hst file where the input data is recorded. From this, you can determine which file has not been correctly read or might have errors, and also which part of that file has been successfully read. If the program reads all the input files, starts successfully but then fails before the iterations begin, then this is often a problem related to the specified flow and speed conditions in the input data or the geometry specification, and these should be checked. These errors are usually related to errors in the units of the specified data (flow conditions, boundary conditions, geometry, empirical data, and so on). A typical user error of this type is that the diameter is needed as a reference value for the size in the flow information (.aer), but the user specifies a radius because the coordinates in the geometry file (.geo) are radius values. Another common error with users is to specify the geometry in inches rather than meters. Another typical user error of this type is that the pressure is specified in bars whereas it is expected to be in N/m2. Other errors may be related to the fact that the specified flow conditions imply choked flow or reverse flow. A useful consistency check of the flow data is made where the following information is printed: Vista TF: Axial compressor calculation -------------------------------------Estimated mean flow coefficient cm/u at first rotor inlet = 0.4567 Estimated mean Mach number cm/a at first rotor inlet = 0.4426

These values may be used to identify if the mass flow, speed and other data have been specified sensibly, as typical values of these parameters for each type of machine will be known. If the program runs, but breaks down after only a few iterations, then this can often be a sign that some of the input data is still not correct because the program is generally very reliable. Here the strategy is to reduce the value of the maximum number of iterations to a lower value than that at which the flow breaks down (reduce the value of the parameter max_it_main in file .con), to rerun the case, and then to examine Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF the results in the .hst and .out files. The errors are usually related to mistakes in the specified data (such as flow conditions, boundary conditions, geometry, and empirical data) rather than mistakes in the numerical method, and these data problems can then often be identified from un-converged results or values provided in the .hst, .txt and .out files. It can also be useful at this stage to examine the plot files of the initial geometry set up by the program, which is named test_prefix.txt or test_prefix.csv. This can often identify aspects of the geometry or flow data that are inconsistent. If the program runs, but the results are extremely unexpected, such that a pump impeller or a compressor stator blade row has been interpreted by the program as a turbine row, then the blade angle definition should be checked. The program attempts to identify the type of blade row from the geometry specified, but in some cases the rules that have been programmed may fail. For example, a compressor stator is identified as a stator blade row which turns the absolute flow towards the meridional direction, that is the blade angle decreases from the leading edge to the trailing edge through the blade row. In some special cases, such as an axial compressor stator with a degree of reaction above 100% or rotor blades with extensive local leading edge recamber, the blade may have other blade forms. In these cases it is possible to specify additional data in the geometry file (see parameter i_row below) to overwrite the program’s own attempts at blade type identification. Geometry produced by BladeEditor contains blade type information provided that, in the blade feature within BladeEditor, a blade type (rotor or stator) is specified.

Convergence The program has several different internal convergence checks, but a converged solution can be achieved only if all of the internal loops also converge, so only one convergence criterion really needs to be checked, which is the convergence of the meridional velocity. The most important convergence check is the maximum error of the local meridional velocity anywhere in the flow field, expressed as a percentage of the local meridional velocity and denoted as error_cm (%) on the screen and in the output files. During the iteration process, the maximum value of the change in the meridional velocity in the whole flowfield between one iteration and the next (delta_cm %) and the location of the maximum error is printed onto the screen every 10 iterations and into the history file for each iteration. The local value of this error is also printed in the output file and into the .csv and .txt plot files. To achieve convergence near machine accuracy, use a maximum value of 0.01% as a convergence criterion. Note that this corresponds to a maximum residual error in CFD terminology of 0.0001, that is 1E-04, which is a much more stringent criterion than the RMS residual error often used in CFD programs of 1E-04. The value of the local error is output for examination with plot software and, for cases that have not converged, it is worthwhile to examine the location of the maximum as this may identify the location of the problem. It is important to remember, however, that numerical methods have many sources of error. In a throughflow calculation, the so-called model errors, related to the fact that the equations we are solving do not really describe the real flow particularly adequately (in this case we solve for inviscid, circumferentially-averaged mean values on widely spaced grid lines) probably outweigh all other sources of error. A solution that is converged to a maximum error in meridional velocity of 0.5% is likely no worse in terms of its agreement with reality than a solution that converges to 0.01% or lower. So calculations that converge to 0.5% can also be considered to be converged for practical engineering purposes. The second convergence check occurs in the innermost mass-flow iteration loop where the program monitors the number of loops required to solve the continuity and radial equilibrium equations on each calculating station. The maximum value of the number of mass flow iterations and the location of the quasi-orthogonal where this occurred is also printed onto the screen and into the .hst file. You can specify the maximum number of loops for the internal mass-flow iteration loop with the max_it_mass parameter in the control file. The recommended value for this parameter is 10. Early in the run, the program usually stops the internal loops when the value of max_it_mass is reached. Later, as convergence is approached, less then 10 internal 140

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Appendices loops are generally required. A typical converged solution may require only 1 or 2 internal loops. The error in the mass flow should be tighter than that for the meridional velocity; a value of 0.001% is currently recommended. The third convergence check occurs in an iteration to a specified pressure ratio and is related to the convergence of the inlet mass flow to a final value and the convergence of the specified target pressures at the trailing edges to a fixed value. These are written onto the output file as error_p and error_mass respectively. The same limit for the mass flow convergence is used as given above and the target pressure convergence is set internally within the program to be tighter than this. Experience shows that it is important in simulations to a specified pressure ratio to ensure that tight tolerances on these parameters are given, otherwise the program modifies the target pressures on the basis of inadequately converged data and divergence may result. In some cases with closely spaced calculating stations (high aspect ratio grid) it has been identified that, although the simulation converges to a relatively low level of the maximum error in the meridional velocity of 0.1% relatively quickly, it does not always continue to converge below this level of error. In these cases you have several options. Firstly, it might be sensible to accept this level of convergence and continue to optimize the geometry of the machine. In some cases, the simulation that is not perfectly converged may indicate the existence of an unwanted flow feature as a cause of the poor convergence. Such features include: anything that creates a tendency for the flow to reverse direction; an extremely high curvature in the meridional channel; a poor grid. A second approach is to make use of other models that are built-in for the damping factors within the program, by reducing the value of the streamline curvature damping factor damp_sc and the velocity level damping factor damp_vl. In some cases it may be helpful to reduce both the value of damp_sc and damp_vl to smaller values than the standard values of 0.25 and 0.40. The most common failure for the program to converge is related to difficulties in the streamline curvature calculation causing divergence of the maximum error in the meridional velocity distribution. If the program identifies a trend for the results to start to diverge then it automatically decreases the damping factors to avoid divergence by causing more damping of the solution. If the errors continue to increase, then further reduction of the relaxation factors tends to freeze the unconverged iteration at the state where the problem was identified so that there is at least no unexpected exit from the program even if the simulation does not converge. Because of this feature it is not advisable simply to increase the number of iterations in the hope that the simulation will converge. A better strategy is to calculate with a large number, say 2000 iterations, and if the simulation does not converge, restart the calculation from the restart file to reset the damping factors to sensible values. This strategy often works in difficult cases. The numerical fix of reducing the damping factors when the error diverges is reported on the screen and in the history file. If this fix does not work, then the calculation of the streamline curvatures may ultimately fail, although this only occurs in simulations that have otherwise started to have serious numerical problems. The ultimate failure here tends to be an error in the subroutine pero, called from subroutine curvature, or in subroutine parabola, called from subroutine streamlines. Both are, in themselves, generally robust. Subroutine pero is a modified interpolation routine along the lines of the so-called AKIMA splines. The breakdown is related to the numerical difficulty of calculating curvatures in a flow when the streamlines are no longer smooth and the spacing of the calculating planes is small. Subroutine "parabola" attempts to fit a parabola through internal data in the program and is also robust until serious problems occur. These errors have mostly been trapped such that an error message is printed and the program exits the calculation without breaking down. In cases where such problems occur, it is often worthwhile simply to run the simulation again from the restart file generated from an earlier unconverged simulation or with a different initial estimate of the flowfield (which is controlled through the initial value of cm_start in the control file), because starting from better initial conditions may clear the problem found in the initial calculation. In choked flows it is generally better to start with a lower value of cm_start, as this will not be choked. If this does not work then again a Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF useful strategy is to reduce the value of the maximum number of iterations to a lower value, say 200 (parameter max_it_main in file .con), and recalculate and examine the unconverged results. It may also help to run the simulation repeatedly with a low limit on the maximum number of iterations because each successive run tends to get to a lower value of the maximum error. If this fails, it is useful to examine the .hst and .out files and plots of the unconverged results. These files and plots can be used to identify aspects of the design that, when improved, allow convergence to be achieved. The program also writes the values of the local error and the local choke ratio into the .txt file so it is possible to examine this and quickly locate the location where the problems are occurring. A value of unity for the choke ratio implies that the flow is choked and a value above unity indicates that the local mass flow is above the choking mass flow of the streamtube. It may be necessary to have some fundamental understanding of how the turbomachine operates in order to identify how to remove these problems. Further comments on choking are given in Choking (p. 142). The program prints an error message if it reaches a state where the maximum change in meridional velocity from one iteration to the next is more than 400% and then it closes down the calculation. Should this occur it is then recommended that you repeat the calculation with the maximum number of iterations set at a value lower than that where the program stopped (see the history of iterations in the output file) and then examine the results for this unconverged point. This can help you to identify the problem.

Reverse Flow Another common failure mode for the program where it has difficulties converging is related to difficulties in calculating reverse flow in the meridional plane; such flow is not possible with the streamline curvature method. If the program observes that reverse flow occurs in the meridional plane, then it attempts temporary fixes to enable the iterations to proceed in the hope that the problem will be cleared. One particularly important fix (that is not reported) is to avoid negative values of the meridional velocity by setting any negative values to 5% of the mid-span value. This may be used in early iterations and later no longer be needed, but if the final “converged” result contains such values, it is not really a valid solution. This can often be identified by a difficulty in convergence at a particular location in the grid. The background to this problem is a fundamental difficulty related to the physics, whereby a strongly swirling flow in an annular duct may separate at the hub or shroud, and the streamline curvature method is inherently unable to calculate such a reverse flow. This problem becomes more serious with calculations of low hub-to-tip ratio. The use of a limit on the meridional velocity on any streamline is reported in the output.

Choking It should be mentioned that the throughflow method is not particularly suitable for choked blade rows because the mean stream surface equations average out the flow in the circumferential direction and are therefore not aware of high Mach numbers on the suction surface of blades. In addition, any shocks that may be present in turbomachinery flows are generally not oriented in the circumferential direction so are smeared out in the circumferential averaging of the flow to determine the mean stream surface. Furthermore, the basic method is inviscid and this precludes the existence of strong shocks. Nevertheless, despite these serious limitations, an attempt has been made to model choking in the blade rows so that, in combination with correlations, the maximum flow and the additional losses related to shocks are taken into account in the overall predicted performance. In this way, the program includes aspects of choking that are compatible with the level of empiricism of typical 1D calculation methods, and may even be more successful than these because the variation of Mach number over the span is taken into account. This is useful in a program intended for design purposes because it helps choking problems to be identified at a relatively early stage in the design process, and aids the understanding of the axial and radial matching of the blade rows as the rotational speed varies.

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Appendices All aspects of special calculations for choking flows are hidden. Setting the parameter i_expert = 0 causes the program to examine choking but not limit the mass flow if choking is found to occur. This is the most robust way to run the program and is recommended for beginners. Expert users can use i_expert = 1, which limits the mass flow according to various choke models. Choking is strongly related to the throat areas between two blade rows, so any real estimate of the choking flow should make use of accurate estimates of the throat areas. In Vista TF the shortest straight-line distance between two blade rows can be specified in the geometry file for each of the input sections, and if the values are not specified (that is, a value of zero is given) then Vista TF makes its own crude estimate of the throat areas based on its limited knowledge of the blade geometry. This estimate is, at the moment, too crude to be used accurately in the calculation of choked blade rows, and may lead to a value for the choked mass flow that is incorrect. It may be worthwhile, in some situations, to run Vista TF with no values specified for the throat and then examine the program´s own estimate of the throat areas, which are in the output file, and then run with slightly larger or smaller values specified in the geometry file, depending on the real throat areas or the choking mass flow if the latter is known. One method that tends to work in the most difficult cases is to remove any calculating planes in the neighbourhood of the throat, as suggested by Denton (1978). Local details of the flow calculation are lost, but the calculation can then be made to converge up to the limiting mass flow. When you specify a mass flow rate, you must ensure that it is not greater than the choking value. The program may generate warning messages if the specified mass flow exceeds the choking value. The output parameter choke_ratio is the ratio of the local mass flux to the maximum possible at that location. A value above unity is not a realistic solution but if the choke parameter i_expert is set to zero then such solutions can be generated. This option is available because the program is sometimes more robust under this operating mode than when i_choke is set to 1 and the full choking models are used. Note that in some multistage computations the actual specified mass flow may be below that required to actually choke the machine, but during the iterations, individual blade rows may still become choked. The program becomes less robust as choking is approached. In some high-speed situations where it is difficult to obtain convergence with a specified mass flow, the restart file can be used to store results for a converged operating point at a lower speed and lower flow, and then the required operating condition can be obtained by starting from the restart file with new flow conditions slowly stepping to the required operating point. In a similar way, it is advisable to first set up a simulation close to the design flow, before attempting to move towards a higher flow with a higher risk of choking. You can run a simulation with a specified pressure ratio. For a choked blade row, the shift to a specified pressure ratio is a more physical approach than specifying the mass flow because, in this case, the solution is indeterminate. In turbines with steep characteristics (little variation in mass flow with pressure ratio) this is reliable. In compressors with flat operating characteristics (large variation in mass flow with pressure ratio) this approach may be more unstable so it is not recommended for calculations close to the expected surge line. Iteration to a defined pressure ratio makes use of the so-called “target pressure” ratio method of Denton (1978). This requires the program to make a first guess of the pressure at each trailing edge of the machine. The algorithm currently incorporated makes a crude estimate of this but it has been found that this may not be sufficient to secure convergence, especially for compressors. For this reason, you have the option to define the first guess of the pressure at each trailing edge (set i_flow = 6 instead of i_flow = 5). Even when using this option, the iteration to pressure ratio for multistage compressors is still very sensitive, and convergence is not guaranteed. If iteration to pressure ratio is used for choked blade rows, then an accurate estimate of the throat widths needs to be provided in the geometry file and the value of i_expert

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Vista TF should be set to 1 so that the limits to the mass flow at choke are imposed. If the throat area feature is calculated by BladeEditor then the throat widths will be calculated and added to the geometry file.

Computational Grid As in most numerical methods, a finer grid leading to a closer spacing of the quasi-orthogonal lines and streamlines will lead to a higher numerical accuracy of the simulation. Closer spacing of the quasi-orthogonal lines for streamline curvature calculations can, however, cause instabilities in the convergence process. This can be overcome by increasing the numerical damping (lowering the relaxation factors) but this causes an increase in computational time, so a compromise is generally needed. The relationship between the needed relaxation factors and the aspect ratio of the computational grid in a throughflow calculation was theoretically derived in a classical paper by Wilkinson in 1970 (see Streamline Curvature Throughflow Theory (p. 118)). His studies showed that close spacing of the quasi-orthogonal lines required more damping. The problem is related to the fact that if the calculating stations are closer together then a small displacement of a streamline can lead to a large curvature. In this case it is only possible to take a small part of the new solution forward each iteration and so the number of iterations increases. Wilkinson derived an equation of the following form to calculate the optimum relaxation factor for a certain grid aspect ratio:

He also showed that the value given here as k2 is actually a function of the Mach number, the flow angle, and of the method used to calculate the curvature of the streamlines. The aspect ratio of the grid (h/∆m) in this equation is the ratio of the calculating station length to the meridional spacing of the grid lines. The equation above was used in older versions of Vista TF to determine the streamline curvature relaxation factor with the numerical values of k1 = 0.5 and k2 = 20/96. The value was based on the largest aspect ratio that can be found in the domain. This is then further reduced if the calculations show any tendency to diverge during the iterations. The largest aspect ratio in the whole grid was used, whereby the meridional spacing is the shortest meridional distance between the two adjacent grid lines. A value of 0.01 for this relaxation factor corresponds to an aspect ratio of around 15 and will lead to long calculation times because only 1% of the new solution can be taken into account and 99% is carried forward from the earlier solution. In order to reduce an error in the initial solution to 0.01% of its initial value then the number of iterations required would be

A value of 0.001 for this relaxation factor (aspect ratio near to 50) would lead to ten times as many iterations. Values of the aspect ratio larger than 15 are therefore not recommended but in cases where this is unavoidable (such as low aspect ratio blades with high span and small chord with internal calculating stations) then the program still converges but at a slower rate. A different stability scheme has been incorporated in Vista TF. In this, the relaxation factor ratio is calculated as:

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Appendices

Where alpha is the absolute flow angle in ducts and stator rows and the relative flow angle in rotor rows. In the new scheme, the relaxation factor can vary from quasi-orthogonal to quasi-orthogonal so that regions of the grid with small aspect ratios are not penalized by a locally poor grid spacing elsewhere. In addition to this improvement, experience with many difficult cases has been incorporated in the selection of the maximum relaxation factor. With this new model, you should not need to adjust the damping factors because the program does this automatically. All flow gradients in the radial equilibrium equation and the curvature of the streamlines in the solution are determined by a piecewise parabolic interpolation through three points. This is a very rapid numerical procedure but experience shows that this can cause errors in the estimation of the curvature of the hub and casing if the quasi-orthogonal spacing is too wide. For the case of an axial to radial bend with circular arc meridional wall contours the error in curvature is of the order 2.5% on a grid with 7 quasi-orthogonal lines (a quasi-orthogonal placed every 15° around the bend). This decreases to 0.2% for 19 quasi-orthogonals (a quasi-orthogonal every 5°). This suggests that typical radial impellers with an axial inducer should be calculated with around 15 quasi-orthogonals in the bladed region. Moreover, the basic assumptions of the meridional throughflow method (for example: no frictional forces, axisymmetric flow, no spanwise mixing) certainly cause larger errors than this error in the curvature estimate. It should be noted that decreasing the convergence tolerance to low values does not eradicate this error, so that for typical engineering applications a tolerance of 0.1% on cm is generally adequate because the curvature calculation is not more accurate than this. A lower value is however generally used because this confirms that numerical convergence has really happened. Using 17 streamlines across the span is recommended. The use of such a large number of streamlines across the span brings little improvement in the accuracy when compared with experimental data compared to using only 9, but nevertheless clearly leads to fewer numerical errors in the integration of the radial equilibrium equation. 17 and 9 streamlines have the advantage that the streamlines split the flow uniformly into 16 or 8 streamtubes. The limitations mentioned above on the calculation of flow gradients and curvature also determine to what extent details of steps in the wall geometry can be taken into account. Steps, kinks and wells in the meridional contour need to be omitted as these features are typically of a sub-grid size. Generally attempts to improve the accuracy by using finer grids with more details are not made in streamline curvature calculations because this is counterproductive. In axial turbomachinery calculations with quasi-orthogonals at the leading edge and trailing edge planes and with flare on the hub and casing walls, inaccuracies will arise because the kinks in the contours cannot be accurately modeled.

Other Numerical Issues Computing a new solution from the restart file of an existing solution, even when no changes have been made in the input data, generally requires 50 or more iterations to re-converge to the solution on the restart file. This effect is due to the fact that the restart file stores only a small part of the information related to the original solution, and many fine details of the solution have to be recalculated. In running the program from a cold start (without a restart file) it is useful to think carefully about the initial value of cm_start that is specified for the control file. This determines the meridional velocity level of the initial solution and it has been experienced that an initial value too far from reality may cause the solution Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF to breakdown. The value that should be specified for cm_start is the flow coefficient (cm/u) of the machine concerned, whereby the reference velocity used is the velocity determined by the reference diameter and reference speed (ref_d and ref_n). In flows with a risk of choking, it is better to use a low value of cm_start to ensure that the initial conditions are not close to choke. When a converged solution is available as a restart file, it should be used because, although it does not necessarily reduce the number of iterations needed, it does make the solution process more robust. The restart file is continually updated by each converged computation, but also if the solution reaches the limit of the maximum number of iterations without converging. In a case where the solution is actually diverging, the non-converged restart file might be a worse starting condition than the program´s own initial guess, so it can be useful to discard this and start again. If a converged solution has been reached then it is sometimes useful to store the converged restart file for a better starting solution if something later goes wrong during calculations at other operating points. As with all numerical methods, the use of unconverged results for design decisions is extremely dangerous and is not recommended. Nevertheless, examination of unconverged results can often be extremely useful for identifying numerical issues. In some cases examination of unconverged results may indicate features of the design that can be changed to avoid such problems by modification of the geometry. One measure that has been incorporated and which may be useful during debugging of a poor calculation is to set the parameter grad_ree equal to zero. This overrides the radial equilibrium equation and leads to a spanwise constant meridional velocity (see below). This can be useful in identifying errors where flow data is inconsistent with the geometry being calculated. Another alternative that can be used with turbines is to specify a near-zero swirl velocity on the mid-streamline at the outlet of the last rotor and let the program determine the mass flow and pressure ratio consistent with this (“iteration to outlet swirl”). This has unfortunately not been thoroughly tested on enough cases to guarantee that it will always work. If all else fails then set i_ree = 3 in the control file. Under these circumstances the value specified as grad_ree in the control file is then used to reduce the meridional velocity gradient as follows:

This can be extremely useful for debugging, because it can allow the program to avoid failing due to high spanwise velocity gradients. In this way, it effectively becomes a mean-line program with no spanwise variation in meridional velocity (if grad_ree = 0.0). Other parameters such as the blade speed still vary across the span, so it is not exactly a mean-line program. Most cases converge under these conditions and this ensures that the axial matching along the mean streamline of the blade rows is approximately correct. When converged it may be possible to approach a solution with the correct radial distributions by slowly relaxing the value of grad_ree towards unity. During this process, the features of the velocity gradients that cause trouble slowly become part of the calculation and this can then help to identify the problem. Cases that do not converge well are usually either poor designs, or are good designs operating a long way from their design point. Non-convergence generally means that the design is a long way from satisfying the condition of radial equilibrium. If the flow solution converges well then this usually means that the flow is automatically close to radial equilibrium and this will generally indicate a higher-quality machine.

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Conversion of a .rtzt File into a .geo File

Appendix G: The RTZTtoGEO Program The ANSYS .rtzt and the Vista TF .geo Geometry Definition File The data in the .rtzt file is the meanline coordinate data as produced by the program BladeGen on a number of layers from hub to shroud, with a format as described in Description of the RTZT File (p. 150). There are several differences to the .rtzt option in BladeGen and the geometry actually needed by a throughflow program, and for this reason the RTZTtoGEO program has been written to convert this data into a more suitable format, rather than working directly with the .rtzt file. The first difference is related to the need for a throughflow program to work with blade angles, in the case of Vista TF with the blade lean angles gamma_r and gamma_z (see Definition of Blade Lean Angles (p. 128)). Throughflow programs work on relatively coarse grids and so it is sensible to provide the programs with the blade angles rather than just the blade coordinates. Otherwise the blade angles would have to be calculated by interpolation and differentiation on a coarse grid which will lead to errors. In axial duct flow programs with planes just at the leading and trailing edges, this is done by specifying the axial blade angles or flow angles at the inlet and the outlet. In Vista TF, which includes the blade force in the solution and is designed for radial machines, both the axial and the radial lean angles (gamma_r and gamma_z) have to be defined and, because the program includes internal planes, these are defined throughout the blade, not just at the edges. The second key difference is that RTZT concentrates on the information required on each stream-surface (or layer) at a certain percentage of the span of the blade, or on blade sections or layers. Throughflow programs concentrate on the information in a plane at right angles to this and require information along equally spaced quasi-orthogonal lines at fixed meridional positions through the blade rows, and upstream and downstream. In .rtzt files, the number of points and spacing in the meridional direction is not the same on each layer. In a throughflow program, it is the location of the layers on each quasi-orthogonal line that may be different, but the points along the streamline must be evenly spaced for all layers. The throughflow program also needs additional data upstream and downstream of a blade row to define the position of the quasi-orthogonal in a region of duct. This is not the case in the current .rtzt file, because different levels of information are available on each layer in this region, and curved quasi-orthogonals outside of the bladed regions are difficult to define. In some of the cases tested with highly curved leading edges, it was necessary to modify the .geo file by hand to avoid problems with the quasi-orthogonals upstream or downstream of the leading edge crossing the leading or trailing edge.

Conversion of a .rtzt File into a .geo File A program, RTZTtoGEO, can be used to generate the geometrical input data file (file extension .geo) for the Vista TF streamline curvature program from the BladeGen RTZT output format (file extension .rtzt). The RTZTtoGEO program can be obtained from PCA, although the preferred method to generate the .geo file is to use the BladeEditor VistaTFExport feature (see Export to Vista TF (.geo) (p. 46)). No guarantee can be given that the RTZTtoGEO program will work on all cases. This program can be used to merge several separate .rtzt files from BladeGen into a single .geo file for multiple-blade-row simulations with Vista TF. For a single blade row, the program makes use of three files: •

One input data file is needed: RTZT geometrical data file (.rtzt).

•

The program creates one output file: Vista TF geometrical data file (.geo).

•

The input and output file names are specified by you in an auxiliary data file that must be called rtzt.fil. It must contain the necessary file names in the following order and form: Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Vista TF Number of blade rows RTZT datafile name Vista TF geometry datafile name

1 impeller.rtzt impeller.geo

For multiple blade rows, additional .rtzt files are needed for each blade row and the associated .geo files are merged into a single .geo file for the whole domain. The number of individual blade rows is given in the first line and the names of the individual .rtzt files follow this. For n blade rows the program makes use of n+2 files: •

n input data files are needed: n RTZT geometrical data files (.rtzt).

•

The program creates one output file: Vista TF geometrical data file (.geo).

•

The input and output file names are specified by you in an auxiliary data file that must be called rtzt.fil. It must contain the necessary filenames in the following order and form:

Number of blade rows RTZT datafile name RTZT datafile name : : RTZT datafile name Vista TF geometry datafile name

n Prefix1.rtzt Prefix2.rtzt Prefixn.rtzt impeller.geo

Note that the different .rtzt files must be generated from BladeGen files that join up to each other consistently with no gaps. If the domains between adjacent blade rows as defined by the .rtzt files meet exactly at the boundary of the domains then the program includes a single quasi-orthogonal at this boundary.

Running the RTZTtoGEO Program The file impeller.rtzt and the file rtztgeo.fil should be in the same directory as the executable of the compiled program files. Starting the program produces the .geo file from the .rtzt file. If the .geo file already exists, there is a prompt as to whether this should be overwritten. The program prompts you to identify whether the blade row is a compressor (pump) or turbine, and whether it is a rotor or stator. In addition the program suggests the number of quasi-orthogonals upstream of the leading edge and downstream of the trailing edge but you can change these numbers if this seems appropriate, simply by replying with n (n = “no”) to the prompt and then suggesting the new number of quasi-orthogonals to be used. If you reply with a y (y= “yes”) then the automatic choice of the program is used, which is fairly sensible in most cases.

Note The limit on the number of points in each layer of the .rtzt files is 1000. The limit on the number of layers is 15. The maximum number of blade rows is 20. Up to 3000 quasi-orthogonals can be included in the final .geo file.

There are options to modify the number of quasi-orthogonals in the blade row and to change the orientation of the calculating grid so that this is oriented in the positive z direction. The change in orientation is needed because in some BladeGen files the flow travels in the direction of the negative z axis, and Vista TF assumes that the flow is traveling in the direction of the positive x axis. Without this switch the hub and shroud contours become reversed. The option to modify the number of quasi-orthogonals in a blade row has been 148

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Merging Several .rtzt Files into a Single .geo File included so that RTZTtoGEO can better cope with axial blades with short chords relative to radial machines with long chords. The program makes its own choice of the number of quasi-orthogonals needed, based on the aspect ratio of the blade; this is more or less consistent with the stability requirements of the Vista TF program. The rule used leads to 16 quasi-orthogonals in most radial compressors. You can change this number if this seems appropriate, simply by replying with n (n = “no”) to the prompt and then suggesting the new number of quasi-orthogonals to be used. If you reply with a y (y= “yes”) then the automatic choice of the program is used, which is fairly sensible in most cases.

Merging Several .rtzt Files into a Single .geo File Vista TF can run a computation for up to 20 blade rows. BladeGen can currently only be used to define the blade rows individually so each .rtzt file contains only a single blade row. It is possible to merge these into a single .geo file automatically using Vista RTZTtoGEO, as explained above. The procedure below describes how to merge individual .geo files by hand, just in case the automatic option fails. 1.

Run RTZTtoGEO for the first blade row.

2.

Set up a Vista TF calculation for this blade row with all the appropriate input files and get this to converge.

3.

Run RTZTtoGEO for the next blade row.

4.

Edit the .geo file of the first blade row to include the additional information for the downstream blade row, as follows:

5.

1.

Change the title section as appropriate (section 1).

2.

Add new quasi-orthogonals in section 3 (copy from the .geo file of the next blade row and add to the .geo file of the first blade row). This may require modifications by hand in the duct region between the blade rows because the quasi-orthogonals have to step smoothly from inlet to outlet and not overlap. Usually this means deleting some quasi-orthogonals downstream of the first blade row and upstream of following blade row where the domains would overlap. Note that the numbering of the quasi-orthogonals does not have to be changed because the program does not read this information. The numbering of each quasi-orthogonal can then be left as originally output by the RTZTtoGEO program. Be careful in this process not to add any extra empty lines to the .geo file between the different lines or to take any away. Note that the type and orientation of the blade row should be correct automatically (with i_type 2 for stators and 3 for rotors) and that the number of upstream and downstream quasi-orthogonals can be modified so that this process is easier.

3.

Do the same for the blade definition section (section 4), whereby only those lines within the blade row need to be copied in.

4.

At the end of the .geo file, the details in section 5 need to be modified to give throat areas for the blade row that has been added (which is actually zero because the ,rtzt file does not provide this information. Thus if there are two blade rows each defined with five sections then there would be 10 lines at the end of the .geo file. These extra lines can also be cut and pasted from the .geo files for the appropriate blade row if you want.

5.

Count the number of quasi-orthogonals that are left and change this in section 2. If you are lucky and have not had to delete any quasi-orthogonals, this is straightforward.

Edit the .cor file of the first blade row to include additional downstream blade row losses, deviation, and blockage data, noting that the location of the deviation is related to the number of the quasi-or-

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Vista TF thogonal and not the blade row. Note that the aerodynamic and control data files (.aer and .con) do not usually need to be changed in this process. 6.

Delete the restart .rst file because the restart capability only works if there has been no change to the number of quasi-orthogonals. Vista TF recognizes this and recreates a new restart file automatically.

7.

Run Vista TF, and repeat from step 3 for each additional blade row. Note that experienced users might manage to make the modifications to the .geo file and the .cor file for several blade rows together in 1 step, but doing it step-by-step gives better control of where any errors have been introduced.

Description of the RTZT File This section describes the generic RTZT data file format for BladeGen. The file is an ASCII file that uses space separation between values.

Note Angular values must be in radians. Example file: text enclosed in {} is a data item text enclosed in () is a comment text enclosed in [] is optional {number of blades} {number of splitters} (0 is main blade only) (for each blade, main and splitter) {pitch fraction} (Ignored for main blade) {number of layers} [N] [T] (Normal or Tangential Thickness Flag) (for each layer) {span fraction} {number of points} [a][t][b] (for each point) {r} {theta} {z} {thickness} : :

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Index

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