What phenomenon occurs when flow reverses in a compressor?

The phenomenon that occurs when flow reverses in a compressor is referred to as surge. Surge is a condition where the airflow through the compressor drops below a certain level, leading to an unstable operating condition. During surge, the flow can actually reverse direction, causing vibrations, pressure fluctuations, and potential damage to the compressor. This typically happens at low flow rates when the compressor is unable to maintain the necessary pressure differential to keep the air moving in the intended direction, leading to a drop in efficiency and effectiveness of the compressor's operation.

Surge is a critical consideration in the design and operation of compressors, as avoiding this condition is essential for the reliable performance of many systems, such as jet engines and various industrial applications. Understanding surge helps engineers and operators ensure that their compressors operate within safe limits to prevent such damaging reversals in airflow.