Why do jet engines need a combustion chamber?

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Couldn’t the compressed air by itself make a plane fly? Or does it need that extra energy from the combustion chamber to make a plane fly?

In: Engineering

4 Answers

Anonymous 0 Comments

What energy do you use to compress the air? Compression of air requires energy and it cant come out of nowhere.

A jet engine has a compressor in the front, the combustion, and then a turbine that is used to drive the compressor. If the compressor drives the turbine the best you could evet get is the same amount of energy and you put into the compressor so no energy to propel the aircraft. In practice, none of them are 100% efficient so it would just stop.

You can compare it to if you use an electric motor to drive the generator that power it. There is losses and it would just stop.
The combustion increases the temperature and the speed of the gas when it passes over the turbine so you have a net increase in energy that can drive the compressor and push out the exhaust to propel the aircraft.

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