gsphelp  Propeller

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gsphelp  Propeller

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AC_Propeller

 

The propeller model component can not only be used to model both fixed pitch as constant speed propeller applications using a specific propeller map format, but also can be used if no propeller map characteristics are available.

 

Propeller type can be specified

Prescribe efficiency
The 'Prescribe efficiency' model uses the ideal (or actuator disc) propeller model to calculate maximum total efficiency (i.e. propulsive efficiency) at which any user specified value exceeding it is truncated. For conceptual design studies where the propeller design has not yet been defined fully (and no map is available), using the ideal propeller model is often the best option. For the ideal propeller theory, refer to the technical (TM) GSP manual. Specify a propeller efficiency to represent a reasonable loss, both for in-lfight and static (Vt=0, and so advance ratio J=0) conditions.

Map / fixed pitch
With a fixed pitch propeller with known D and pitch angle, use a propeller map and manually specify the propeller pitch (beta) angle and also the design point in the map. For map scaling, often it is best to specify DP at in-flight conditions. Note that setting up a model where the power turbine is configured with a power balance equation, power setting Wf as free state and power turbine / propeller speed is user specified is the preferred model setup. In this model setup, the model finds the required power level to maintain propeller speed. In fact, now fixed propeller speed is the power setting input variable in this configuration. Although alternative configurations are possible (i.e. propeller speed as free state instead of Wf) these usually are much less stable and not recommended.

Map / pitch control
With a variable pitch ('constant speed') propeller, use a propeller map and use a propeller control to specify propeller pitch (beta) angle. Make the propeller control input a free state and configure the power turbine with the power balance equation. Power setting input is Wf or TIT (TT4). The propeller pitch angle will then be found corresponding propeller torque and power matching the power turbine delivered power. Set OD propeller speed by adapting power turbine speed. For map scaling, often it is best to specify DP at in-flight conditions, such as 1000 m / Ma 0.2 in this example model configuration.

 

Warning:

Note that the Prescribe efficiency propeller model option has been introduced and added on top of the existing propeller options in version 11.4.4.0! One may need to update propeller component data from older/existing models.