how to modify the jet engine model?

I need to modify the simscape model(ssc_turbojet) to thrust control if I could identify where the fuel rate equations affect the engine model (I would need to add some Simulink blocks to simscape that make the mass flow rate a PI function of Current Thrust-Desired Thrust). Does anybody have an idea how to do it?

Thanks.

Answer 1

[Sebastian Castro]

Looks like in the example, the fuel rate isn't manipulated at all. The control input to the burner is simply the burner temperature T4.

If you look at the source code of the block inside the "Performance" subsystem, you'll find that the fuel/air ratio is calculated using the temperature difference between compressor (T3) and burner (T4) and the calorific value of the fuel (QR), which is a parameter of this Performance block.

Fa == ((T4/T3)-1)/(QR/(c_p*T3) - T4/T3);

So I think what you need to do is take that relationship and invert it such that you input the fuel/air ratio and use that to compute the actual burner temperature T4. If you do this, you can then control the fuel rate based on thrust.

- Sebastian