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In a gas turbine engine, a diffuser is used to reduce the velocity of gas entering the combustion chamber, to...
  • A
    reduce the gas pressure and ensure that the combustion does not stop.
  • B
    increase the gas pressure and ensure that the combustion does not stop.
  • C
    increase the gas velocity through the combustion chamber.
  • D
    reduce gas temperatures and decrease the risk of overheating the combustion chamber.

Learning Objective 021.11.02.02.21: Describe the function of the diffuser.


DIFFUSER
The diffuser is the divergent section of the engine after the compressor and before the combustion chamber. The diffuser increases the cross-section of the duct, for a constant mass flow, the velocity drops. This increases the static pressure of the air. Additionally, it decelerates the approx. 350 m/s flow to an approx. 50 m/s flow before fuel injection in some engines. This deceleration is crucial for optimal fuel burning conditions. It prepares the air for entry into the flame burning area of the combustion section at a lower velocity (and with much higher pressure) so that the flame of combustion can burn continuously. If the air passed through the flame area at a high velocity, it could extinguish the flame.

Therefore, it stops the flame being extinguished by the high dynamic pressure of the air, by turning a lot of that into static pressure.

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