FAA Powerplant Written Practice Test

What characterizes a double entry centrifugal compressor?

1. Vanes located on one side only

2. A single entry point for air

3. A compressor with vanes on both sides of the impeller

4. Multiple impellers arranged in series

The correct answer is: A compressor with vanes on both sides of the impeller

A double entry centrifugal compressor is characterized by having vanes located on both sides of the impeller. This design allows the compressor to draw in air from two sides, which enhances its efficiency and increases the volume of air that can be compressed. By integrating vanes on both sides, the compressor can balance the aerodynamic forces acting on the impeller, resulting in a smoother operation and higher performance. This configuration also contributes to a more compact design while allowing for a higher flow rate compared to compressors that only have a single entry point. In contrast, a configuration with vanes on one side would limit airflow, and a single entry point would be typical of simpler compressor designs. Multiple impellers arranged in series refer to a different arrangement known as a multistage compressor, which is not indicative of the double entry characteristic. Thus, the presence of vanes on both sides of the impeller is what distinctly identifies a double entry centrifugal compressor.