How does a Jet engine work?

[Mark77]

I watched some stuff on youtube and read some also. I understand that it compresses the air and therefore give thrust. But I don`t exactly understand what drives the compressor or the fan blades? And how does the process start? and how can it be ajusted, or made more effective? Maybe I missed something or maybe I am just plain stupid :doh But some enlightment would be nice :-)

[Holden_C04]

google is your friend: How a Jet Engine Works (http://inventors.about.com/library/inventors/blhowajetengineworks.htm)

[Joel_MD]

The expanding hot gasses spin a turbine before they exit the exhaust nozzle. The turbine turns a shaft that is connected to the compressor fan blades toward the front of the engine.

[imported_themightytimmah]

What he said, plus some of the bigger engines need an external cart (with a 454 v8 in some cases) to get them started up. Jet engines are notoriously inefficient at startup since not much air wants to flow in.

[imported_smprince1]

Google search produced this easy to understand explanation:



There are 4 parts and this is what they do:



1. The compressor which is used to increase the pressure (and temperature) of the inlet air.



2. One or more combustion chambers in which fuel is injected into the high-pressure air as a fine spray and is burned creating heat the air. The temperature in the chamber rises during combustion, so the hot air needs to occupy a larger volume than it did when cold, so it expands through the turbine.



3. The turbine which converts some of this temperature rise to rotational energy. This energy is used to drive the compressor.



4. The exhaust nozzle which accelerates the air using the remainder of the energy added in the combustor, producing a high velocity jet exhaust.



See a video of how all this happens courtesy of GE here-



Engines 101 (http://www.geae.com/education/engines101/)



And just like your car engine, a starter motor is used to get it all started.

[miahman98]

I always thought it was magic. Thanks a lot guys. :cry:

[gmblack3]

The "starter motor" is an APU or Auxiliary power unit.



Auxiliary power unit - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Auxiliary_power_unit)



Most aircraft have them in the tail section.

[imported_Devilsown]

Dont forget the good ol Start carts they use on B-52`s and the Aircarts. Also HowStuffWorks - Learn How Everything Works! (http://www.howstuffworks.com) I`ve killed many hours there.

[Mark77]

That GE link was very helpful, thank you all

[wannafbody]

I think hundreds of hamsters spin the turbine:spit: