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In which part of a gas turbine engine are high temperature requirements most critical for the materials used?
  • A
    The last part of the HP compressor and front part of the HP turbine.
  • B
    The turbine and exhaust nozzle.
  • C
    The combustion chamber and front part of the HP turbine.
  • D
    The combustion chamber and exhaust nozzle.

Combustion chambers, the first turbine stage (HP), and their associated parts are very prone to deterioration because of the high stresses and temperatures to which they are subjected. A deteriorated combustion chamber has various cracking and buckling that will distort the flame pattern and eventually burn the outer case, causing a flow disruption.

To control and minimize the stress on the combustion chamber’s components and avoid high-temperature stress over the HP turbine, some of the compressed air from the HP compressor is ducted via a secondary path for cooling of the inner casing. Considering that combustion occurs at around 2000°C, the supply of cooler air could drop the temperature at the outlet of the combustion chamber down to 1000°C -1500°C, which would be within the limits for the HP turbine. Additionally, turbine blades can be film cooled by passing a small film of cold air over the surface of the blades, or internally cooled where cold air passes inside the turbine blades through several ducts.

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