### 6.2.3. Geometry Tab

Figure 6.3: Geometry Tab

Frame 1: Inducer

This frame contains the parameters relating to the impeller inlet section. It is separated into three sections: Hub, Shroud, and Leading edge.

- The Hub frame enables you to specify the Diameter, Vane inlet angle and Vane normal thickness. The Vane inlet angle is optional. The radial distribution of beta angles may be calculated using either a tangent or sine formula.

- The Shroud frame contains geometry data for the inducer at the shroud. You can specify the Diameter and the Vane normal thickness. The Diameter has the following three settings:

  - You can specify the shroud diameter value directly.

  - You can specify the Vane inlet angle and have the program calculate the appropriate diameter accordingly.

  - You can select Optimise diameter where the program calculates the appropriate diameter to achieve a minimum inlet relative Mach number.

- The Leading Edge frame accepts the following geometry data for the leading edge of the impeller: Location on shroud and Angle of inclination.

  The Location on shroud option allows you to specify where the leading edge of the impeller begins expressed as a percentage of the meridional length along the shroud (0 to 100 percent).

  The Angle of inclination option allows you to specify an angle between 0 and 90 degrees inclusive to account for the inclination of the leading edge. An angle of 0 degrees represents a leading edge that is radially aligned while an angle of 90 degrees represents a leading edge that is axially aligned. Alternatively, the leading edge can be defined to be perpendicular to the hub curve in the meridional view by selecting Normal to hub.

  The Location on shroud and Angle of inclination features can be used to accommodate impeller designs for more industrial, lower specific speed compressors where the leading edge is typically placed farther downstream in the radial section of the impeller and is often axially aligned.

Frame 2: Diffuser

Vaned or Vaneless may be selected. Vaneless activates an empirical correction to the baseline stage efficiency obtained from correlations.

Frame 3: Impeller Shroud and Clearance Geometry

Unshrouded or Shrouded impeller may be selected. The Axial Tip Clearance can either be given as a fraction of the vane height, or directly as a specific value.

Frame 4: Axial Length Ratio

Automatic or User specify may be selected.

Frame 5: Other Impeller Geometry

This frame contains other miscellaneous geometry data required for the calculation, specifically the following:

- Main Vanes

- Intervanes

- Backsweep Angle

- Rake Angle

- Vane Roughness (choices of Machined Finish or Cast Finish)

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