This feature creates a new blade relative to an existing (main) blade such that the new blade (or splitter) shares the same flow path, tip clearance, and blade count, and is generally assumed to be part of the same blade row. The Reference Blade of this feature is the selected Blade feature; only one Blade feature can be selected per Splitter feature.
The Splitter feature can have 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 are discussed:
A cloned splitter shares the same blade shape as the main blade, but is offset in theta from the main blade.
The feature properties are as follows:
|
Details of [Feature Name] | |
|
Splitter |
[Feature Name] |
|
Operation |
[ Add Material | Add Frozen ] |
|
Reference Blade |
[Blade feature selection] |
|
Type |
Clone |
|
Offset |
[Angle | Pitch Fraction] |
|
Pitch Fraction or Angle |
[Value: 0-1]
[Value] |
If your case involves features other than the Blade/Splitter, you can set the Operation feature property to "Add Frozen" to reduce computational time while you are designing the Blade/Splitter. However, with the "Add Frozen" option, bodies other than the Blade/Splitter will not be updated in response to changes in the Blade/Splitter. If you have other features that are dependent on the Blade/Splitter, you should set the Operation feature property to "Add Material" to allow the other features to be affected by the Blade/Splitter.
The Offset specifies how the splitter will be offset relative to the main blade. If "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 * π / n
where n is the number of main blades.
An independent splitter can have a completely different shape than the main blade (except that the blade clearance properties are inherited from the main blade). An independent splitter shares the same blade count as, 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] | |
|
Splitter |
[Feature Name] |
|
Operation |
[ Add Material | Add Frozen ] |
|
Reference Blade |
[Blade feature selection] |
|
Type |
Independent |
|
Offset |
[Angle | Pitch Fraction] |
|
Pitch Fraction or Angle |
[Value: 0-1]
[Value] |
|
Offset Reference (Only for "Offset" set to "Pitch Fraction") |
[Hub at Leading Edge | Hub at Trailing Edge] |
|
... (The remaining properties are similar to those of the Blade feature selected for the Reference Blade.) | |
If your case involves features other than the Blade/Splitter, you can set the Operation feature property to "Add Frozen" to reduce computational time while you are designing the Blade/Splitter. However, with the "Add Frozen" option, bodies other than the Blade/Splitter will not be updated in response to changes in the Blade/Splitter. If you have other features that are dependent on the Blade/Splitter, you should set the Operation feature property to "Add Material" to allow the other features to be affected by the Blade/Splitter.
The interpretation of the Offset is different for an independent splitter than for the cloned splitter. If "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:
An offset reference meridional location is calculated at the intersection of the hub contour and the splitter leading edge contour.
For the offset meridional location, the main blade theta value is calculated from the main blade cambersurface.
The reference theta is then calculated by adding the angular offset (from the pitch fraction or specified angle) to the main blade theta value.
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:
An offset reference meridional location is calculated at the intersection of the hub contour and the splitter trailing edge contour.
For the offset meridional location, the main blade theta value is calculated from the main blade cambersurface.
The reference theta is then calculated by adding the angular offset (from the pitch fraction or specified angle) to the main blade theta value.
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.
An independent splitter (as opposed to a cloned splitter) has its own CamThkDef sub-features if its Reference Blade is a (main) blade that is defined using CamThkDef sub-features (as opposed to blade section (airfoil design mode) sub-features). The properties of a CamThkDef sub-feature of an independent splitter are the same as those of a CamThkDef sub-feature of a main blade (described in Camberline/Thickness Definition Sub-feature), with the following exceptions:
The Angle Definition property has an extra option, From Reference Blade, that causes the angle data to become the same as that of the main blade for the length of the splitter camberline. You can select From Reference Blade then User Specified if you want to make the angle definition editable but initialized from main blade data.
The Thickness Definition property has a corresponding extra option with similar behavior.