[alepal]

Hi, I am doing a jet engine simulation where I am mostly interested of getting the suction and exit-temperature of jet engine correct. The simulation is a steady state simulation.

I know the delta pressure of the engine and the massflow of fuel into the engine. For the compressor pressure increase I have made a subdomain with a general momentum source with deltaP/LengthCompressor.

For the combustion I have a second subdomain where I put an energy-source term with the fuel energy based on the massflow fuel in.

Have I forgot something? Because I can not get the solution to converge, the residuals does not reach acceptable levels (I want it down to at least RMS 1xe-4). I have tried relaxation-methods (Local timescale factor=5), mesh refinement etc. Is there something that I should keep in mind?

Thanks in advance

[D.B]

1) Have you simulated the turbine for pressure loss ?
2) Are you ensuring your cycle parameters like all component exit and inlet temperatures are maintained
3) What about mass flow rate ?

Check if you basic cycle is maintained, if all that is done, see in which region are the residuals going high, or where the parameters first go haywire and way beyond the cycle limits, that should help you out.

-D.B

[alepal]

No I have not simulated the pressure loss in the turbine, when I tried to do that I encountered strange moving flow where the flow started to flow backwards...

I am simulating the engine in an ambient domain with ambient temperature for that height, so the only temperature I control is the combustion chamber temperature.

When adding a continuity source it asks for velocity of the massflow which I dont know. I do know the thrust which it gives so I am trying to make the model give me this thrust...

Where the paramaters go haywire? Do you mean to keep a look on the iteration where everything goes nuts? What does that tell me if I don't know exactly where that is?

[D.B]

See, you need to know a mass flow rate.

Let me put it in another way.

1) What is exactly your domain ? Can you put a rough sketch here ?
2) What are your inputs, maybe put them in the picture?

The reverse flow might be due to excessive back pressure, whatever happens you need to put a turbine.

3) How are you planning to put a turbine ?
4) There should be a nozzle at the aft, what about that ?
5) There should be a nozzle exit bc, what is it ?

If you give me more details maybe I can answer in a much better manner.

[alepal]

In the picture you can get a rough picture of what I am doing. I create a pressure increase in the compressor domain but if I do it in the turbine at the same time everything explodes...

The deltaP input is 5 times the ambient pressure (which is 1 atm).

Nozzle exit bc? The flow should just expand freely in the flow, otherwise I haven't done any nozzle exit bc. Except an outlet in the main domain with a relative static pressure of 0.