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How a Jet Engine Works



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Like all good inventions, the jet engine is a simple design. It was an invention inspired by Sir Isaac Newton's third law of motion, which states that 'for every action, there is an equal and opposite reaction'. This can be demonstrated by an inflated balloon. When the nozzle of the balloon is released, the 'action' of escaping compressed air results in the 'reaction' of the balloon's movement in the opposite direction.

To get a clear idea of how a jet engine works it's useful to remember four words: suck, squeeze, bang and blow. Air is 'sucked' into the engine by a fan; it is then 'squeezed' by a multi-bladed device called a compressor; this compressed air then moves into a combustion chamber where fuel is added and the mixture is ignited; the resulting 'bang' leads to rapidly expanding gases which 'blow' through a turbine and are then expelled through the rear of the engine. As the gases exert equal force in every direction, and as they have only one escape route, the reaction (or thrust) propels the engine forward. The spinning turbine operated by the exhaust gases creates energy that is used to operate other parts of the engine such as the fan and the compressor, resulting in a continuous process.

A jet engine is an internal combustion engine, just like the engine in your car. In both engines the air is drawn in, compressed and ignited, and the expanding gases produce power. But unlike your car engine, which produces combustion in a series of separate explosions and transmits the power by means of pistons and cranks, a jet engine produces continuous combustion and the power is generated by the escaping exhaust gases. This makes for a simpler design. As the jet engine developed, it was found that by mixing fuel with the exhaust gases, additional thrust (after-burn) could be produced. Afterburner sections were added to high-performance aircraft to allow quick surges of thrust when needed, such as during take-offs and fast climbs, but they are used sparingly due to high fuel consumption.

Since their development in WWII, jet-powered aircraft have revolutionized travel. The incremental increases in speed that were being achieved by the 1950s meant that a new generation of airliners could be designed that were able to link continents, and people could travel with a speed impossible before the invention of the jet engine. Rapid international travel is now commonplace, and although concerns are being raised by the environmental impact of mass airline flights, there is no doubt that the invention of the jet engine has been one of the key developments in the history of technology.


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