How does combustion happen in a JET ENGINE?



How does combustion happen in a JET ENGINE?

In: Engineering

Perpetually. When the compressed air is halfway through the turbine, it meets many nozzles that are fixed on the shell of the turbine and spray kerosene vapor into this burn chamber. Because everything is so hot, this kerosene combusts almost immediately and produces more heat which exhausts through the rear of the engine

In a normal engine, the combustion is contained within the cylinder; the metal of the cylinder, piston, and seals keep the gases and the fire inside the cylinder.

In a jet engine, the combustion is “contained” by the huge quantities of air that’s sucked in the front and forced to move towards the back. The speed of this air moving through the jet engine is faster than the speed of burning of the jet fuel, so the flames and the expanding gases have no choice but to push out the back of the engine, and not out the front. Think of it as a cylinder that’s made of a wall of air, rather than of metal.

Compression plus ignition, the fans compress the air/fuel mixture and it combusts due mainly to the compression, it is more of a burn than an explosion. That turns the turbine which pulls compressed air in, which is combusted, more air comes in etc and the reaction continues until you cut the fuel out. The actual turbine is behind the compression/combustion stages, so the turbine is rotated by the rapidly expanding gases, this is connected to a shaft that turns the compressor blades in the front. Since the blades in the turbine are at an angle relative to the speeding gases, they rotate and generate torque. There is a type of jet engine called an orbiting combustion nozzle jet where the whole combustion chamber rotates with the turbine and compressor blades. The rotating energy caused by traditional jet engines is typically just lost, in this case you allow that energy to add to the torque on the shaft. The twisting power in that type of jet is both due to the expanding gases hitting the turbine fan blades *and* the rotating force caused by the combustion.

In traditional turbojets the escaping gases is the mode of propulsion, in bypass turbofans it is actually the big fan up front pushing air through the bypass.