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How a Jet Engine Works



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"How a Jet Engine Works"
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Jet engines work by burning some sort of fuel in an oxygen rich atmosphere to produce heat forcing an increase in a differential pressure. The jet turbine works by forcing air into a combustion chamber, the air has to be compressed by a series of fans to achieve a high enough level of compression to be efficient and effective. Once the air is at a high enough density there are small nozzles that release the fuel into the air mix at a highly controlled rate according to the required power and the available oxygen. The air fuel mix is usually continuously ignited but there are some forms off jet engines such as the primitive pulse jet engine which have a resonant frequency of operation and works on pulsed ignitions. They are a bit of a lost art because they are incredibly simple to build but far too inefficient and underpowered for any real applications. Back to the real jet engine, in the ignition chamber the gasses expand as the fuel burns in the oxygen creating a tremendous increase in pressure. Then the exhaust pushes another series of fan blades which are usually directly connected to the blades of the compressor. Thus the exhaust will drive the compressor when the proper compression ratio is achieved. The energy can be captured in many forms, you can take as much energy as possible out of the exhaust and directly tap the rotor for power as in a helicopter type situation. Or you can use the kinetic energy of the gasses leaving the engine for thrust, like on a jet fighter or passenger plane. A passenger plane type huge engine has an additional front compressor blade set as scientists have found that a single fast moving stream of air coming out the back of the jet engine generates less thrust than when it has some of the power moved to the outer surrounding of the stream, thus the exhaust is tapped to move the extra set of blades. This works by transferring more of the fuel energy to the air directly in the immediate tail end of the engine. The thrust is generated by the expansion of the gas as the chemical energy in the fuel and the oxygen in the air is released to increase the kinetic energy of the molecules which increases the temperature and thus the pressure, therefore we have a pressure differential across the engine which 'pushes' the engine forward, and allows them to power the airplane. On a jet fighter an afterburner can generate additional thrust by injecting more fuel into the exhaust, the idea is that the particles are colliding with or pushing on the back end of the engine and particles not pushing as hard on the front.

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