FAA Powerplant Written Practice Test

Which component of a centrifugal flow compressor performs work similar to the rear stator vanes in an axial flow compressor?

1. Compressor rotor

2. Diffuser

3. Inlet guide vanes

4. Compressor housing

The correct answer is: Diffuser

The correct answer is the diffuser. In a centrifugal flow compressor, the diffuser plays a crucial role in converting kinetic energy from the high-velocity airflow that exits the impeller into pressure energy. This process is similar to the function of rear stator vanes in an axial flow compressor, which also serve to efficiently convert the kinetic energy of the moving air into pressure. The design of the diffuser creates a larger cross-sectional area that allows the fluid to slow down and increase in pressure. As the air moves through this component, its speed decreases, which raises the static pressure of the air, making it more suitable for the combustion process in a gas turbine engine. In contrast, the other components mentioned do not serve the same function as the diffuser. The compressor rotor is responsible for imparting energy to the airflow, increasing its velocity rather than converting kinetic energy to pressure. Inlet guide vanes adjust the airflow entering the compressor but do not contribute to the pressure increase after the impeller. The compressor housing primarily encloses and supports the compressor components rather than playing an active role in energy conversion.