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I was doing research about jet engines, and they seem really difficult to fully understand. So, can anyone explain it in a simple way?

Jet Engine Image

How do jet engines work?

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I gotta say, that engine doesn't seem to be terribly well tethered. I guess those two longer guy wires and the short turnbuckle (per side) are sturdier than they look. – FreeMan Jan 9 '15 at 16:19
Could anybody (OP ?) source the image ? – kebs Jan 9 at 18:37
up vote 13 down vote accepted

In the simplest of terms:

  • Suck - Air is sucked into the turbine. For efficiency reasons, most aircraft let some of that just pass through the outer part of the fan, rather than through the whole engine.
  • Squeeze - The compressor squeezes that air together to a high pressure. This helps with ignition.
  • Boom - Fuel is injected and ignited. As the air gets hot, it expands.
  • Blow - The hot air drives the low-pressure turbine (driving the whole shaft holding the engine together), sucking new air in, and is itself blown out the back.


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There's a great interactive animated GIF at NASA's K-12 page on jet engines. – egid Mar 26 '14 at 18:44
if some of the air bypasses the engine it is called a turbofan engine. but that is semantics – ratchet freak Mar 26 '14 at 19:05
the "suck" part is in effect only at startup/on ground. During cruise is the motion of the aircraft w.r.t. the air that makes the air enter the engine. The fan effectively pushes the air towards the back. – Federico Mar 27 '14 at 13:43
@ratchetfreak I'd always heard that a "low-bypass" jet engine was still a turbojet and not a turbofan, but other definitions refute that. Some specialized engines, like those for the SR-71, had variable bypass; they were technically turbojets up to Mach 2, then the bypasses were opened and air flowed directly to the afterburners. – KeithS May 27 '15 at 2:56
@KeithS Federico is right, engines only "suck" in air when they are at no or very low speed. I think Federico was not commenting on the fact that in order to suck in air the pressure in the inlet has to be lower than the ambient pressure. This means there is a pressure gradient from high ambient pressure to low static pressure in the intake. During cruise flight this is not the case anymore, then the ambient static pressure gradient reverses. – rul30 Jan 8 at 8:31

A jet engine is an overcomplicated ramjet with extra turbines to let it work at lower speeds.

A ram jet works by igniting compressed incoming by mixing it with fuel and providing a spark.

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hmmm... a ramjet lacks (moving) compressor stages, which are an essential component of a jet engine, and there is no bypass component and most of the time no supersonic flow. So perhaps more distant relatives than siblings? – yankeekilo Mar 26 '14 at 19:32
@yankeekilo that's why I said overcomplicated :) – ratchet freak Mar 26 '14 at 19:38
LOL, but then a barrel of fuel and some matches may also claim commen ancestry :D – yankeekilo Mar 26 '14 at 19:44
A ramjet is almost totally different from a turbojet (and its derivatives). It lacks a fan/compressor and a turbine, so it would only confuse people to compare them. Once you have a turbojet down, you can look at pulsejets, ramjets, scramjets, and other more esoteric forms. – Phil Perry Mar 26 '14 at 22:49
I don't see why you say it's "overcomplicated" -- it seems that a jet engine is exactly as complicated as it needs to be for its intended operating environment. – Johnny Mar 26 '14 at 23:43

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