Compressing Air: The Foundation of Thrust
A turbojet ingests ambient air and compresses it through multiple axial compressor stages, raising pressure by a factor of 15 to 45. This compression requires enormous power — in a large engine the compressor absorbs up to 50 MW, all extracted from the turbine downstream. The simulation models ideal compression with an isentropic relationship, showing how pressure ratio directly determines the cycle's theoretical efficiency ceiling.
Combustion and the Temperature Limit
Fuel is sprayed into the compressed air and burned at nearly constant pressure, raising gas temperature to 1400-1900K. This is the hottest point in the engine and the primary design constraint. Higher turbine inlet temperature means more energy available for thrust, but the turbine blades must survive thousands of hours in this environment. Modern blades are single-crystal castings with labyrinthine internal cooling channels.
Turbine and Nozzle Expansion
The high-pressure, high-temperature gas first passes through the turbine, which extracts just enough energy to drive the compressor. The remaining enthalpy accelerates through a convergent (or convergent-divergent) nozzle to produce a high-velocity exhaust jet. Thrust equals the mass flow rate multiplied by the velocity increase from inlet to exit.
Flight Speed and Ram Effect
At flight Mach numbers above 0.3, the inlet acts as a diffuser, slowing incoming air and converting kinetic energy into additional pressure — ram compression. At Mach 2, ram compression alone provides a pressure ratio of about 7.8, significantly supplementing the mechanical compressor. The simulation shows how thrust and efficiency change across the subsonic and supersonic flight envelope.