FAA Powerplant Written Practice Test

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

1. Compressor impeller

2. Diffuser

3. Compressor housing

4. Air filter

The correct answer is: Diffuser

In a centrifugal flow compressor, the diffuser plays a crucial role analogous to the rear stator vanes found in an axial flow compressor. While the compressor impeller is responsible for accelerating the air, the diffuser is essential for converting some of that kinetic energy into pressure energy. As the high-velocity air exits the impeller, it enters the diffuser section, where the design typically causes the air to decelerate. This deceleration results in an increase in static pressure, which is the primary function of the diffuser. Essentially, while the axial flow compressor uses stationary stator vanes to achieve a similar conversion of energy, the centrifugal flow compressor relies on the diffuser for this purpose. The other options, such as the compressor impeller, primarily focus on imparting energy to the airflow rather than converting kinetic energy to pressure. The compressor housing serves as a casing for the components but does not perform work on the airflow. Lastly, the air filter has no role in the compression process itself but rather functions to clean the air entering the compressor. Thus, the diffuser is the component that shares this specific function with the rear stator vanes of an axial flow compressor.