Surge is a kind of abnormal amplitude that occurs when the air compressor capacity is reduced to certain level. Centrifugal compressor is a type of engine compressor, which can be seriously damaged by the surge.
For centrifugal compressor, the typical phenomena of surge are: 1. The inlet pressure of compressor increases in the beginning and then abruptly decreases. This is accompanied with periodic fluctuations; 2. The air compressor capacity rapidly decreases and is accompanied with fluctuations; 3. The current and power meter of the engine that drives the compressor will appear unstable. This is accompanied with periodic fluctuations; 4. The engine has strong amplitude while having abnormal airflow noise.
There are three methods that are commonly used to solve the surge issue. 1. Add bleed valve on the compressor to discharge the superfluous gas; 2. Use twin or triple rotor compressor; 3. Use adjustable blades. When the airflow inside the centrifugal compressor and pipeline system is reduced to the minimum amount, periodical airflow oscillations will be found in the system because the compressor air path suffers from serious airflow separation and the intersection of the pipeline and compressor performance curves is within the boundary of surge. If the pipeline capacity is bigger, the surge amplitude will be bigger and the frequency will be lower; if the pipeline capacity is smaller, the surge amplitude will be smaller and the frequency will be higher. Surges can intensify the noises, damage the blades, vibrate the unit, damage the bearing and ultimately results in serious accident.
※ Cited from the article of “Ren Ren” website.