FAA Powerplant Written Practice Test

What is the role of the diffuser in a centrifugal flow compressor?

1. To accelerate airflow

2. To reduce air velocity and increase pressure

3. To mix air and fuel

4. To cool the compressed air

The correct answer is: To reduce air velocity and increase pressure

The role of the diffuser in a centrifugal flow compressor is to reduce air velocity and increase pressure. As air is drawn into the compressor, it is accelerated by the impeller, which imparts kinetic energy to the air. Once the air exits the impeller, it enters the diffuser section, where its velocity decreases due to the expanding passage. This reduction in velocity allows the kinetic energy to be converted into pressure energy, resulting in increased static pressure of the compressed air. This process is fundamental in ensuring that the compressed air can be properly directed into the combustion chamber or into subsequent stages of compression. By effectively performing this role, the diffuser ensures efficient operation of the centrifugal flow compressor, which is critical for maintaining the performance and efficiency of the overall engine system.