gsphelp  Specifying transient simulation input

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gsphelp  Specifying transient simulation input

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Quick start basics - Your first simulation session .

 

For transient simulations, input parameters need to be specified as a function of time. The engine response to that input change is then calculated. In GSP the input-time functions are specified using time-input tables in the input specification windows.

Again, let's take the fuel flow to determine the response in time. Assume the engine response on the following fuel flow vs. time function is desired:

a fuel flow change from 0.38 (max. thrust) down to 0.1 in 1 second (deceleration),

a 5 seconds stabilisation at this fuel flow,

a fuel flow increase to 0.38 again (an acceleration) in 1 second

finally followed by 5 seconds stabilisation again.

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To obtain this input, do the following:

1.Click in the project tree panel on the ReferenceModel node (configuration model) to load the original configuration. Now add a new case model (name it "Transient case") and set the case type to Transient (confirm to save changes).
2.Enter the Fuel Control input dialog window (double-click the icon). Click the Transient tab sheet.

Here the time-function table for fuel flow is visible. At the top row at time 0.000 the design fuel flow is already specified.

3.Click A to add a line and enter 1 as the time value.

When analyzing transient performance, an engine response calculation is usually started after a short period of running steady state, in this case 1 second at the design steady state operating point.

4.Enter 0.38 in the fuel flow column Wf[kg/s] in the last row (click on it to edit).
5.Continue steps 3 and 4 to obtain the table shown in the figure below. Edit the time-fuel flow table using the navigation controls ButtonTransientNav to go to the first line, previous line, next line or last line or to add, insert or delete a line in the table, or to delete the entire table. Note that fuel flow changes in infinite short times are invalid: a gas turbine engine control system would never be able to realize it and GSP will likely not be able to simulate it. So make sure you enter time values with reasonable (not too small) positive increments between the rows.

Table Transient Fuel

6.Optionally click Graph to view the transient input curve.
7.Check if transient input activated is checked and click OK (put a check mark in Active checkbox to activate the series).

 

Hint: you may want to Reinitialize the model prior to a steady-state series simulation in order to bring the model state back to Design point before new input is specified.