### 10.3.3. 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. 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.

Blade profiles can be defined in two ways:

- By referring to angle and thickness definitions (CamThkDef sub-features: see Blades made using Camberline/Thickness Sub-features) to define the blade profiles, or

- By referring to blade sections and their theta positions (Blade Section sub-features: see Blades made using Blade Section (Airfoil Design Mode) Sub-features).

#### 10.3.3.1. Blades made using Camberline/Thickness Sub-features

When using the Camberline/Thickness blade design mode, the blade shape is defined on flow path layers according to angle and thickness definitions.

In the tree view, when using the Camberline/Thickness blade design mode, CamThkDef sub-features appear as sub-nodes of the Blade feature (or Splitter feature, if the Splitter is of Type “Independent”). For details on CamThkDef sub-features, see Camberline/Thickness Definition Sub-feature.

When using the Camberline/Thickness blade design mode, the feature properties of the Blade/Splitter feature are as follows:

Details of [Feature Name]
Blade | [Feature Name]
Operation | [ Add Material | Add Frozen ]
Blade Design Mode | [ Camberline/Thickness | Airfoil ]
Flow Path | [FlowPath selection]
Type | [Rotor | Stator]
Number of Blade Sets | [Integer Value]
Surface Construction | [General | Ruled Element | Flank Milled | Radial Element]
Blade Extension (%) | [Value] [a]
Shroud Tip Clearance | [None | Layer] This property also affects any and all splitter blades.
Shroud Tip Layer (Only for “Shroud Tip Clearance” set to “Layer”) | Layer number at which to make a blade tip (at the shroud end of the blade). This property also affects any and all splitter blades.
Flank Milled Extension (for flank milled only) For details, see Flank Milled Blades.
Hub Layer | [ 0 < Value < 1.0, 0.1 ]
Shroud Layer | [ 0 < Value < 1.0, 0.1 ]
Leading Edge Details
LEContour | [Sketch selection]
Type | [Ellipse | Cut Off | Square] [b]
LE Ratio at Hub (for Ellipse only) | [Value]
LE Ratio at Shroud (for Ellipse only) | [Value]
Trailing Edge Details
TEContour | [Sketch selection]
Type | [Ellipse | Cut-off | Square] [c]
Ellipse Ratio at Hub | [Value]
Ellipse Ratio at Shroud | [Value]
Advanced Properties (Hidden by default)
Number of Points Along the Blade (for all blades but flank milled) | [Int Value]
Total Number of Points (for flank milled only) | [18 <= Value, 100] This is the total number of defining points for a layer (including points in the flank milled extension, if applicable).
Number of Points for LE (for Ellipse only) | [ 6 <= Value, 25 ]
Number of Points for TE (for Ellipse only) | [ 6 <= Value, 25 ]
Camberline/Thickness Definitions: [number]
Layer 1 | Yes
Layer 2 | [Yes | No]
... | [Yes | No]
Layer n | Yes

[a] If the topology on the shroud end cap of the blade does not match the shroud topology (shroud contour edges), the blade has not been trimmed cleanly. In order to correct the trim, increase the Blade Extension.

The same applies for the hub end cap topology as compared with the hub topology (hub contour edges).

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

[c] 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).

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 (e.g. fillets) 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 first Type property specifies whether the blade is a rotating or stationary component.

Before constructing the blade surface via lofting, BladeEditor interpolates lines that connect corresponding points on blade profiles. Each blade profile is governed by a CamThkDef sub-feature that defines a camberline, thickness distribution, and data controlling the number of profile points. In this section of the documentation, the term camberline refers to CamThkDef sub-feature.

The angle and/or thickness data of one profile may or may not be dependent on such data of another profile, depending on the Angle Definition and Thickness Definition settings of each camberline. Furthermore, the Angle Definition and Thickness Definition settings may be constrained to have particular values depending on the Surface Construction option.

The Surface Construction options are:

- `General`

  If the Surface Construction property is set to `General`, then no dependencies are enforced. Each camberline may be specified independently of the others.

- `Ruled Element`

  If the Surface Construction property is set to `Ruled Element`, then you must use exactly two camberlines: one on the hub layer and one on the shroud layer. No other camberline is allowed.

  For the camberline on the hub layer, both Angle Definition and Thickness Definition are software-enforced to be User Specified.

  For the camberline on the shroud layer, each of Angle Definition and Thickness Definition can be User Specified or Interpolated.

- `Flank Milled`

  Flank milled blades represent a special case of blade geometry definition where the blade pressure and suction surfaces are described by only two layers, typically one at the hub and one at the shroud (or tip).

  For details, see Flank Milled Blades.

- `Radial Element`

  If the Surface Construction property is set to `Radial Element`, then (by definition) all camberlines have the same theta value at any given axial coordinate. In such a blade, angle data is set only for the camberline on the hub layer.

  Figure 10.5: Contour plot of theta (θ) versus radial (R) and axial (Z) coordinates on a blade defined with `Radial Element`

  The Angle Definition for the camberline on the hub layer is software-enforced to be User Specified, whereas the Angle Definition for each of the other camberlines is software-enforced to be Interpolated.

  To ensure adequate interpolation accuracy (for the angle data) you should use at least five camberlines when using the `Radial Element` option.

  In cases where the axial coordinate range of the camberline on the hub layer does not encompass the axial coordinate ranges of all other camberlines, the software will issue a warning message and might produce a faulty geometry. In such cases, you should consider using a different Surface Construction option.

  In cases where the hub curve is tangent to a plane of constant axial coordinate, the blade geometry is over-specified near the hub. In such cases, the software might produce a faulty geometry.

When a curve in the angle or thickness view is modified, the properties displayed for the corresponding CamThkDef sub-feature are updated simultaneously, but the graphics view will not be updated until you regenerate the Blade.

##### 10.3.3.1.1. Adding/Removing CamThkDef Sub-features

When a new blade or splitter is created, CamThkDef sub-features are created automatically for the Hub and Shroud layers. When a new layer is added to the flow path, the layer will appear in the Camberline Definitions group, but will be marked as 'No' to indicate that it is not a defining layer.

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 might fail. Adding additional camberline definitions (especially where the leading/trailing edge curve deviates the most from the blade shape) should fix this problem.

Whenever the Camberline Thickness Definition Layer property is set to ‘No’, no CamThkDef sub-feature exists under the Blade/Splitter for this layer. Also in this case, no information is displayed in the Angle, Thickness, or Auxiliary Views for this layer.

When a Camberline Thickness Definition Layer property is switched from 'No' to 'Yes', a CamThkDef sub-feature will be created for the Blade or Splitter, and the data will initially be interpolated from the existing blade data. The Angle Definition and Thickness Definition properties of the CamThkDef sub-feature will both be set to ‘User Specified’ so that the angle and thickness data is editable (otherwise it would remain interpolated from the existing blade data, but would be uneditable).

When a layer that was used for a CamThkDef sub-feature is removed from the flow path, the Blade or Splitter feature will generate an error. The error can be corrected by inserting a new layer in the flow path at the same layer index, or by switching the Camberline Thickness Definition Layer property for that layer to 'No' (therefore deleting the associated CamThkDef sub-feature). In the latter case, the layer will be removed from the list. If you insert more than one layer into the flow path after deleting a layer, the CamThkDef should be reconnected automatically to the layer with the closest average span value.

##### 10.3.3.1.2. Flank Milled Blades

In BladeEditor, you can create Flank Milled blades. This option is applicable only to blades with one cut-off end.

Flank milled blades represent a special case of blade geometry definition where the blade pressure and suction surfaces are described by only two layers, typically one at the hub and one at the shroud (or tip). During manufacture, the milling tool cuts the full depth of the blade passage at once, whereby the milling tool path is implicitly described by the milling lines on the surface of the blade. These milling lines give the surface a ‘ruled’ shape between the two defining layers. The milling lines extend beyond, and do not need to be parallel to, the cut-off end. For this reason the cut-off is typically created as a separate machining step.

The milling machine will enforce some limitations on the rate of orientation change that is acceptable between adjacent milling lines, but otherwise you are free to adjust the distribution of milling lines to achieve the desired blade shape.

Flank milled blades are available for Blade and Splitter features that use the "Camberline/Thickness" blade design mode. To begin making a Flank Milled blade, set the Surface Construction property to "Flank Milled".

The Flank Milled Extension properties (namely Hub Layer and Shroud Layer) control the lengths of profile extensions for the blade: one on the hub layer, the other on the shroud (or shroud tip) layer. The extensions allow ruling lines to be defined slightly beyond the cut-off edge (see Figure 10.6: Flank milled blade extension). Each extension length is interpreted as a fraction (between zero and one, default: 0.1) of a base length. All blades (including any splitter blades) use the same base length, which is the average meridional length of the main blade (the arithmetic average for the two defining layers).

Figure 10.6: Flank milled blade extension

You can adjust the (per layer) total number of defining points and the number of points that define the elliptical edge.

Under the View menu, there is an option to turn on the visibility of the ruling lines, called Blade Ruling Lines.

Requirements For Flank Milled Blades:

- There must be two defining layers: one at the hub and one at either the shroud tip or shroud. Both layers must have angle distributions; one or both have thickness distributions; no other layers can have angle or thickness definitions.

- Either the leading edge or trailing edge must be elliptical; the other edge must be cut-off. The elliptical edge must be straight as viewed in the axial-radial plane.

- Blade lofting is in the streamwise direction.

Limitations:

- There can be no gap between the blade and the hub.

- Blade Design Mode must be set to "Camberline/Thickness", not "Airfoil".

#### 10.3.3.2. Blades made using Blade Section (Airfoil Design Mode) Sub-features

When using the Airfoil blade design mode, the blade shape is defined by a stacked sequence of airfoil sections. The airfoil sections are defined on the flow path layers, as with the Camberline/Thickness mode. The basic topology of each blade section (the set of edges that describe the shape of the airfoil) is defined by the section template, which is shown in Figure 10.7: Blade Section Sketch Template.

In the tree view, when using the Airfoil blade design mode, Blade Section sub-features appear as sub-nodes of the Blade feature . For details on Blade Section sub-features, see Blade Section (Airfoil Design Mode) Sub-feature.

When using the Airfoil blade design mode, the feature properties of the Blade feature are as follows:

Details of [Feature Name]
Blade | [Feature Name]
Operation | [ Add Material | Add Frozen ]
Blade Design Mode | [ Camberline/Thickness | Airfoil ]
Section Orientation | [ Positive | Negative ]
Flow Path | [FlowPath selection]
Type | [Rotor | Stator]
Number of Blade Sets | [Integer Value]
Surface Construction | [General | Ruled Element]
Blade Extension (%) | [Value] [a]
Shroud Tip Clearance | [None | Layer] This property also affects any and all splitter blades.
Shroud Tip Layer (Only for “Shroud Tip Clearance” set to “Layer”) | Layer number at which to make a blade tip (at the shroud end of the blade). This property also affects any and all splitter blades.
Meridional Stacking Definitions
Stacking Method | [LE/TE Contours]
Section Reference Location | [Section Origin | Airfoil Centroid | LE Camberline Point | TE Camberline Point | Chord Midpoint | Throat MidPoint ]
LE Contour | [Sketch selection]
TE Contour | [Sketch selection]
Location | [Inside Contours]
Section Definitions [number]
Section1 on Layer1 | [Yes]
Section2 on Layer2 | [Yes | No]
... | [Yes | No]
Sectionn on Layern | [Yes]
[a] If the topology on the shroud end cap of the blade does not match the shroud topology (shroud contour edges), the blade has not been trimmed cleanly. In order to correct the trim, increase the Blade Extension. The same applies for the hub end cap topology as compared with the hub topology (hub contour edges).

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 (e.g. fillets) 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 Section Orientation property specifies how the blade section is oriented with respect to the Theta direction. The choices are as follows:

- Positive - makes the suction side of the blade face the low-Theta direction.

- Negative - makes the suction side of the blade face the high-Theta direction.

When you make a change to the Section Orientation property, the section input data is preserved so that the section shape is effectively mirrored.

The FlowPath selection is the reference to the FlowPath feature, which is mandatory.

The Type property specifies whether the blade is a rotating or stationary component.

You can turn defining sections on or off from an existing airfoil design mode blade feature. This gives you flexibility in controlling the blade shape without having to recreate the blade feature.

You control which sections are defining sections in the details view for the blade feature. The blade property group Section Definitions lists all available sections. The property value for each section has a `Yes` or `No` value depending on whether it is a defining section (`Yes`) or not. When the blade feature is first created, all sections are marked as defining sections. The hub (Layer1) and shroud (Layern) are always defined.

If the flow path layers are modified, updating the blade feature shows any added sections in the blade Section Definitions. Newly added sections are marked as not defining sections unless you change the property value. Existing defining sections remain unchanged.

You cannot delete a flow path layer if a section is defined on it. If a section definition is switched from `Yes` to `No`, the section data will be preserved (including save/resume) until the flow path layer is deleted. Therefore, you can switch it back to `Yes`, keeping the previous data, as long as the layer still exists. The hub layer and shroud layer are always defined.

In the details view, each section name includes the number of the layer on which the section is defined (for example, Section1 or Section2). In the tree view, under the blade feature, the only section sub-features listed are the defining sections; their names correspond with the names in the details view.

Note that Airfoil Design mode is not compatible with the following features:

- Throat Area

- Export Points (meanline)

- Stage Fluid Zone

- Vista TF Export

- Splitter Blades

- Radial Element Blades

Release 18.2 - © ANSYS, Inc. All rights reserved.