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Effect of high temp. compressor

  1. May 30, 2005 #1
    If the compressor in a turbojet is at high temperatures, it will heat up the air while compressing it.
    Does it have a negative effect on propulsion? If so, then is it because it reduces the efficiency of the burner as well as hampers the intake of air by increasing its pressure delivering greater resistance to the fluid flow into the inlet?
  2. jcsd
  3. May 31, 2005 #2
    Yes...you are correct. You do not want to use the compressor to heat the gas because you are producing friction and putting some resistance on your compressor. You want to let the burner do the work here because you get energy much more effeciently from the chemical reaction as opposed to trying to REALLY REALLY REALLY compress the air. Remember, we do have a temperature limit. The gas is the hottest at the burner exit and the turbine blades must be able to withstand these temperatures. Thus too hot of a burner exit temperature is not desirable. The thermal effeciency the ratio of the useful power to the total power input. Thus we need to reduce the wasted power. The best way to do this is for the exhaust gas to be expanded down as close to its inlet enthalpy as possible. In this situation the turbine could essentially indefinitely power the compressor alone and all the power added in the combustor would be transferred into thrust.
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