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

A compressed air engine is basically like a steam engine; it works, but the fuel storage requirements are high. Airplanes wouldn’t be viable; you wouldn’t have enough compressed air to go very far.

Gasoline engines, and similarly jet engines, release and use the huge amounts of chemical energy “trapped” in gasoline / jet fuel. To understand the amount of extra power, let’s use the gasoline engine as an example: with 4 cylinders, at any time, one is sucking in air and fuel, one is pushed to compress that air/fuel to an extremely high pressure, one is releasing the burnt smoke and carbon dioxide, and one cylinder is in the process of conflagrating (it’s not quite a military-grade explosion) the air/fuel *and creating power*.

That one cylinder produces enough power to not just compress air and otherwise “overpower” the other 3 cylinders, but also run the oil and water pumps attached to the motor, the alternator (generator) for recharging the battery, and your air conditioning system, with enough power left to peel tires or go 0-60 in a few seconds.

There are a number of jet engine designs, but in all of them the combustion overpowers air compression and other “ancillary” systems attached to the engine, so basically without the energy released by combustion it just wouldn’t work.

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