A jet engine is a gas turbine engine. A gas turbine engine, like all good ideas is really pretty simple. Here's how you do it. Get yourself three things:
  • A compressor-any arrangement of blades that when spun will take inlet air and compresses it into a high pressure and temperature. The higher pressure creates higher yields from combustion.
  • A combustion chamber-this is where you squirt your fuel into and it will combust. Once you start a jet engine, fuel is injected and combusted constantly, so you'd better make it a good one, and you'd better make sure it can contain the combustion without blowing up the engine. Within the combustion chamber, there is a fuel source injecting fuel into the compressed air, and a constant flame front, so as fuel is injected into the air and ignited by the the fuel burning in front of it, and combustion occurs continuously until the engine is shut off.
  • A turbine-a set of blades that will spin as the ignited, expanding air from the combustion chamber moves through them. The turbine is connected to the compressor so that the engine compresses using the energy from combustion.
  • A final drive turbine-another set of turbines connected to a drive shaft. These can spin helicopter rotors, turbofans, propellers, etc.

Obviously jet engines aren't simple, or everyone would have one, but the concept is fairly simple. The trick is that jets are spun at very high rpms and high temperatures for long periods of time. This means that special bearings and drives must be made, epecially since the shaft connecting the compressor and the turbine runs through the center of the combustion chamber. The other reason that jet engines aren't common for most applications is that they are difficult to throttle. They make good power at a certain speed, but have trouble making power over a range, something a piston engine excels at. Another interesting thing is that a jet engine is an external combustion engine, unlike a piston engine.