### 5.2.2. Geometry Tab

Figure 5.7: Geometry Input Tab

Annulus dimensions:

Outer diameter, Hub/tip rotor in and Hub/tip rotor out.

These values specify overall annulus geometry. An outer diameter that is too small for the duty will give loadings that are too high and DeHaller numbers that are too low. Equally an outer diameter that is too large for the duty will produce too much swirl and associated pressure loss.

The hub/tip ratios at inlet and outlet are often the same, although it can be an advantage to have a higher outlet hub/tip ratio than that at the inlet in order to accelerate the axial flow and prevent stall. Machines with a low hub/tip ratio commonly have a high hub loading and may require adjustments using the hub loading parameter.

IGV:

Aspect ratio, Number of vanes and Profile trim.

The aspect ratio is defined as the blade height/hub chord. Acceptable values for aspect ratio are between 0.5 and 10, although values between 3 and 5 are more common.

The number of vanes is simply the number of IGV vanes in the bladerow. Acceptable values for the number of vanes are between 3 and 100, although values between 10 and 30 are more common.

The profile trim is defined as the chord at the tip chord/hub chord. Acceptable values for profile trim are between 0.2 and 1.8. Often the profile trim for a rotor will be < 1, reducing the chord with increasing span, and the corresponding IGVs and OGVs will have a profile trim > 1 in order to maintain a constant gap between bladerows.

Entries for Rotor and OGV are similar to those for IGV. The entries for IGV and OGV will be disabled accordingly depending on the machine configuration.

Machine configuration:

Check boxes indicating whether an IGV and/or OGV will be included in the calculation.

Units:

Option buttons to select either SI or Imperial units. This impacts both input data and results and may be switched at any time with immediate effect.

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