Compressor surge

Compressor surge is an unstable, oscillating flow reversal in a turbocharger’s centrifugal compressor when mass flow falls too low for the pressure ratio, crossing the surge line on the compressor map. It produces loud pulsations, heavy thermal and mechanical loading, and can wreck the rotor. It shows up during fast load shedding, fouled turbines, or running too far off the matched point; the surge margin between the operating point and the surge line is the design safeguard.