Compressor Head Performance Curves
(Adiabatic, Polytropic, and Actual Head Curves)
A head performance curve describes the relation between the compressor head and the actual inlet volumetric flow rate. This curve may be supplied on an adiabatic, polytropic, or actual basis. The supplied head can be either on length or Sp.Energy (Energy/Mass) basis. At least two sets of values at different flowrates are required for PRO/II.
Fan Laws are applied to modify the head performance curves when the operating speed of the compressor is different from the reference speed. The Fan Law's exponent has a default value of 2.0 and can be changed if needed.
Usage
From the Compressor Main Window...
1. Select the desired head performance curve (adiabatic, polytropic, or actual) and push the Enter Curve button. The Head Performance Curve Window will be displayed.
2. Select the Head Basis length or sp.energy. Default is Length.
From the Head Performance Curve Window ...
2. Enter values for volumetric flowrate and the corresponding head developed in the table. At least two pairs of values at different flowrates must be entered. These values cannot be referenced using the Define system.
3. Change the Fan Law's exponent if required.
4. Click OK to accept the entered values or Cancel to cancel the operation. The Compressor Main Window will be displayed.
From the Compressor Main Window ...
5. If the compressor's operating speed is different from the reference speed, enter the values for Reference and Operating Speed parameters.
Usage (Multiple RPM)
From the Compressor Main Window...
1. Select Multiple Compressor Head Performance Curves to enter data at multiple RPMs and click the Enter Curve button. The Multiple Head Performance Curve window will be displayed.
2. Select the Head Basis length or sp.energy. Default is Length.
From Multiple Head Performance Curves Window …
3. Enter a value for RPM and click Enter Curve button. The Multiple Head Performance Curve Data window will be displayed.
From Multiple Head Performance Curves Data Window …
4. Enter values for volumetric flowrate and the corresponding head performed by the compressor in the given table. At least two pairs of values at different flowrates must be entered. These values cannot be referenced using the Define system.
5. Surge and Stonewall Points are optional. The volumetric flowrate and the head corresponding to the number entered here will be considered as these points.
6. Click OK to accept the entered values or Cancel to cancel the operation. The Compressor Main Window will be displayed.
See Editing Tabular Data for additional information on editing operations for the head curve table.
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