gsphelp  How to...

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gsphelp  How to...

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This section contains descriptions of a number of GSP tasks which usually are performed very frequently. Either use the help index or the contents section to find help on how to perform a specific task not listed below.

 

Q:        How do I calculate a steady state point at a specified gas generator speed?

A:        In case of a manual fuel control component: Set the fuel flow as a free state in the component options, set the compressor speed to 'Externally controlled' and set the gas generator turbine model option to "Power balance at rotor speed'. Specify the required turbine rotor speed.

In case of a governor or custom fuel control component model, use the 'Fully trimmed steady state (no droop)' option to have GSP find the fully stabilized steady state operation point for the specific control input (input PLA determined demanded rotor speed).

 

Q:        How do I calculate power and/or torque output of a turboshaft engine?

A:        The best way is to add a Load Control component for flexible control of the turbine load, also as a function of time. Activate the Shaft Power PW and SFC check boxes in the Output Options|Global Output Parameters tab sheet to get the typical primary turboshaft power output data. Alternatively the Net power/torque output option in the Load control component output tab sheet may be used to obtain power and torque output for the Load Control only (which usually equals total load).

 

Q:        I get unexpected off-design results, results deviating from the design point where they should not. Wat causes this behaviour?

A:        A cause may be inadvertent settings of off-design operating conditions such as ambient/flight conditions or deterioration. Make sure all these are set correctly (initially/usually equal to design settings) in all components.

Note that the 'Auto reset input to design' General model option automatically resets all of these back to design during a design calculation. With this option off, all off-design inputs remain, even during design point calculation.

Finally, make sure any inadvertent transient inputs do not require unreasonable operating conditions: deactivate the transient inputs in the transient tabsheets if they have more that a single row but are not to be used.

 

Q:        GSP cannot find a steady state (or transient) operating point (Error message: 'Number of steps exceeded limit of ...'). How do I fix this?

A:        Although GSP has a very powerful solver, due to the very non-linear nature of gas turbine characteristics there are cases (complex models/control laws/operating conditions) where GSP cannot find the operating point. The best approach to avoid GSP from getting 'stuck' somwhere is to start calculating points in small steps from the design point onwards, using the steady state series or transient modes. Also manually one can adapt fuel flow for example in small steps starting at the design value.

If the above message appears it is often best to recalculate the design point again and proceed from there with small steps.

The error may also indicate there is no solution at all (for example: with a very low fuel flow, there may not exist a steady state operating point at all).

Another cause may be inadvertent settings of off-design operating conditions such as ambient flight conditions or deterioration. Make sure all these are set correctly (initially/usually equal to design settings) in all components.

Note that the 'Auto reset input to design' General model option automatically resets all of these back to design during a design calculation.

Finally, make sure any inadvertent transient inputs do not require unreasonable operating conditions: deactivate the transient inputs in the transient tabsheets if they have more that a single row but are not to be used.