Jet engine propulsion works on the principles of Newton’s third law of motion where every action has an equal or opposite reaction. In this case in order to ensure the engine attached to the aircraft is moving forward, you need to have a counter force to move in the opposite direction which in this case is the “combusted air” exiting the engine through the exhaust. There so many more intricate details like cold exhaust and different types of combustion chambers etc that makes the modern jet engine so interesting.
In the area of combustion, to simplify it fuel and air is combusted which causes a rapid expansion of air that then exits the exhaust to generate thrust. A quick google search would contain many great pages, articles and documents on this.
This is a little more complicated as you have so many moving components to simulate an entire jet engine. So I would assume the only conceivable way to do so would be to simulate the individual sections of the engine, inlet duct, fan, compressor, diffuser and then save each of those data points before inputting that into the combustion chamber to generate further data. Simulation of just the combustion portion is totally viable and has been done, in fact some of my fellow coursemates are performing such analysis as for their projects, albeit for a smaller engine.
Hope this helps and if you’re planning to run a simulation on a combustion chamber that would be pretty cool!