FAA Powerplant Written Practice Test

What is the primary advantage of an axial flow compressor over a centrifugal flow compressor?

1. Lower weight

2. Greater pressure ratio

3. Higher efficiency at lower speeds

4. Simpler design

The correct answer is: Greater pressure ratio

The primary advantage of an axial flow compressor over a centrifugal flow compressor is indeed its ability to achieve a greater pressure ratio. In axial flow compressors, air flows parallel to the axis of the rotor, allowing for multiple stages of compression without significant stall issues often encountered in centrifugal flow compressors. This design means that axial compressors can compress air more efficiently and effectively at higher ratios, making them ideal for high-performance applications such as jet engines. Additionally, the construction of an axial flow compressor enables continuous acceleration and diffusion of air as it moves through the stages, which contributes to this higher pressure ratio. This characteristic differentiates it from the centrifugal compressor, which typically has a more limited pressure rise per stage due to its design and operation. These features make axial flow compressors better suited for applications requiring high-speed operations and significant changes in pressure, such as those found in commercial aviation and large gas turbine engines.