Question

1.What is the purpose of the diffuser section of a gas turbine engine, and under what principle does it operate?

2.Why do some axial flow gas turbine engines use multiple compressors?

3.What happens in a compressor stall?

4.Why is a variable exhaust nozzle required in an engine equipped with an afterburner?

Answer 1

1. Diffuser is positioned before the compressor section, slow the velocity of incoming air and convert it into pressure. It also changes the radial air flow direction to longitudinal flow before directing it into the combustion section.to maximize the Air flow in a Streamlined Direction

Principle of Diffuser

• diffuser is "a device for reducing the velocity and increasing the static pressure of a fluid passing through a system”. Diffusers are used to slow the fluid's velocity while increasing its static pressure. ... Both mass flow rate and Bernoulli's principle are responsible for these changes in pressure, and velocity.
• An average, single-stage, centrifugal compressor can increase the pressure by a factor of 4. A similar average, single-stage axial compressor increases the pressure by only a factor of 1.2. But it is relatively easy to link together several stages and produce a multistage axial compressor. In the multistage compressor, the pressure is multiplied from row to row (8 stages at 1.2 per stage gives a factor of 4.3)
• A compressor stall will result in a loss of thrust and is likely to produce a "backfire" like sound due to reverse airflow. It may also be accompanied by flame from either or both of the engine inlet and engine exhaust. A sustained compressor stall can result in engine damage and can lead to engine failure
• nozzles have a variable geometry to give different exit areas to control the operation of the engine when equipped with an afterburner .this is because to increase the combustion efficiency and specific thrust of the engine