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chinleng • Dec 28, 2012

How does aircraft gas turbine works?

Hi all

Would like to know about how does aircraft gas turbine engine work.
I have watch you tube video and google on it. But seem to have some doubt.
From my understanding, air is being suck into the compressor, which increase the pressure of air. Some percentage of compress air will pass through the combustion chamber and some will get into the combustion chamber. There will have a fire to ignite the compress air to let it increase in temperature. where lead to the turbine to rotate and also rotate the compressor fan blade. and the rest of air is use as thrust to drive the aircraft to be in the air.
My question is: 1) why does temperature increase help to increase the thrust of the aircraft. 2) what is the purpose of fuel in aircraft? is it constantly supply to maintain the fire in the combustion chamber?
zaveri • Jan 5, 2013
1) temperature increases the energy of the flowing gas, and hence it has more velocity.

this velocity leads to a rise in kinetic energy, and hence the more the kinetic energy, the more speed the turbine blades will rotate with.
G.D • Jan 12, 2013
hi,
# you are right about the working, but compressed air from compressor goes to combustion chember where fuel is added to air and it is ignited(ignition is only at the beginning after that flame is self sustaining, you don't need the igniter anymore); combustion takes place.
# combustion increases temp to the large extent.
# high pressure high temp combustion gases in turn rotate the turbine which in turn rotates the compressor and is power house for other auxiliary systems.
# after passing through turbine; hot gases go to nozzle, where because of its shape, their velocity(Cj) increases.

basically thrust of an aeroplane is;
F=m(Cj-Ca)
where,
m= mass of air
Cj= exit velo.
Ca= airplane velo.

# after the compression in the compressor, the pressure rise is not upto the level to drive turbine and to produce required thrust. only fuel combustion can produce that.(otherwise we wouldn't require fuel at all).
# more is the temperature, more is the velocity at the exit but we need to limit the temp from turbine blade considerations(they cannot withstand very high temp and get damage).
G.D • Jan 12, 2013
if you have any further deep doubts, please ask freely. will be happy to satisfy you.😀