### 8.2.1. Aerodynamics Tab

Figure 8.1: Aerodynamics Tab

Frame 1: Operating conditions

This frame contains the basic flow parameters at the design point:

- Inlet stagnation temperature

- Inlet stagnation pressure

- Mass flow rate

- Expansion ratio t-t

- Rotational speed

- Blade speed ratio (U/C t-t)

Frame 2: Efficiencies

This frame contains two sub-frames:

- Stage

  The stage isentropic efficiency options are Correlation and User specify.

  The default option is Correlation for which either the `Suhrmann` or `Baines` correlation can be chosen to calculate the stage efficiency. If User specify is selected, you must enter the total-total stage efficiency in the text box.

- Nozzle

  You must enter the total-static efficiency of the nozzle. The nozzle efficiency is defined as:

  Where is the inlet stagnation temperature and and are the static and isentropic static temperatures at the nozzle exit, respectively. The default value of 0.9 for the nozzle efficiency is representative in many cases.

  Here the term ‘nozzle’ refers to the part of the geometry that is upstream of the impeller and that controls the flow direction at the impeller inlet. This geometry could be a set of inclined blades, a bladeless inlet scroll, or a combination of both.

Frame 3: Fluid properties

This frame contains the gas property options.

To define the fluid properties, you can either input fixed values of gas constant (R), specific heat at constant pressure (Cp), or request that the program find its own values. The latter facility is selected by clicking either the Air or the Air fuel ratio option. The program will then compute Cp at each station through the turbine from a polynomial expression in terms of local temperature (and, if selected, air-fuel ratio) for pure air or for a combustion products mixture defined by the air-fuel ratio. The program also then provides a value for gas constant.

Frame 4: Flow Angles

This frame contains the Inlet Angle and the Exit Angle frames.

- The Inlet Angle frame contains the Zero relative inlet angle option which indicates zero incidence at the leading edge. When this option is selected the absolute inlet angle must be specified.

  The inlet angle can either be specified as a relative or absolute value, except when the Zero relative inlet angle option is selected.

- The Exit Angle frame enables you to specify the exit angle in either relative or absolute terms unless Zero relative inlet angle is selected. In this case, the exit angle is calculated by the code.

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