What are the successive changes imposed on air flowing through an axial engine?

The correct answer outlines the key processes that air undergoes as it moves through an axial engine. Initially, air enters the engine during the intake phase, where it is drawn into the engine by the forward motion of the aircraft. Once inside, the air is compressed by the axial compressors, which increase its pressure and temperature. This compression is essential for efficient combustion, as higher pressure leads to better fuel-air mixing and more efficient burning of the fuel.

Following compression, the next phase is expansion, which occurs in the turbine section of the engine. Here, the high-pressure, high-temperature air expands as it passes through the turbine blades, converting thermal energy into mechanical energy. This energy is then used to drive the compressor and support the operation of the engine.

Finally, once the air has expanded and given up its energy, it exits the engine in the exhaust phase. This expulsion of exhaust gases creates thrust that propels the aircraft forward. This cycle from intake through compression, expansion, and exhaust is critical to the functioning of axial flow engines, making the correct answer a fundamental aspect of jet propulsion.