FAA Powerplant Written Practice Test

What is the compression ratio of an axial flow compressor primarily a function of?

1. Blade design

2. Number of compressor stages

3. Air temperature

4. Fuel type

The correct answer is: Number of compressor stages

The compression ratio of an axial flow compressor is primarily influenced by the number of compressor stages. Each stage within the compressor typically includes a rotor and a stator, which work together to compress the air as it flows through. As the air passes through additional stages, each stage increases the pressure of the air, leading to a higher overall compression ratio. The design and configuration of the blades in each stage do play a role in the efficiency and performance of the compressor, but it is the number of stages that directly allows for greater compression. Therefore, if more stages are added, the air can be compressed to a higher ratio before exiting the compressor. Other factors, such as air temperature and fuel type, do impact the overall performance of the engine and may affect operating conditions, but they do not fundamentally determine the compressor's compression ratio as the number of stages does.