Chamber non-premixed combustion pressure
 

Hello.

I am explaning my case, I have a combustion happening in the combustion chamber of a rocket. This combustion is supposed to happen at 34 bars, and then the gaz is exiting through the nozzle, where the exterior is 1bar.

The problem being that, for my combustion, I define the combustion pressure to be 34 bar ( Operating condition ) , and define my outlet to be -34 bar ( gauge ) pressure.

The problem is, when i do my simulation, the results give me that the combustion chamber is at 1.7e04 PA (absolute) and the exit pressure is n at 0 bars

How can I do, so the pressure are met ?
Thank you !