How do the different jet engines work on aircraft—the turbojet, the turbofan, and the turboprop?
All three engines start with a turbojet engine. In a turbojet engine, a stream of air is first compressed by a rotary compressor. The air is then mixed with fuel and the mixture is burned. Finally, the hot burned gases are allowed to expand through a rotating turbine and they flow out of the back of the engine at very high speed. To understand how all of this works, let’s follow the flow of energy through the turbojet engine. Assuming the plane is moving forward, the air is moving fast when it encounters the engine’s inlet duct. This inlet duct slows the air down substantially and the change in its speed causes the air’s pressure to rise—an effect observed by Bernoulli. The air’s energy doesn’t change, but its kinetic energy (energy of motion) is partially converted to pressure potential energy. The now pressurized air is further pressurized by its passage through the rotary compressor at the front of the turbojet. The compression process adds energy to the air by doing mechanical work
