Explain compressor surge and how the surge margin is maintained.

Explain compressor surge and how the surge margin is maintained.

• A. Surge is flow reversal due to high pressure; margin maintained by over-bleed.
• B. Surge is a stall in the compressor blades causing noise; margin maintained by thicker blades.
• C. Surge is flow reversal due to low pressure; margin maintained by staying within compressor map, using bleed air, and scheduling.
• D. Surge is a combustion instability phenomenon.

Answer: (C)

Compressor surge is a flow instability in which the compressor cannot sustain the required pressure rise at the current mass flow, causing the flow to reverse briefly through the stages and create large oscillations. The surge margin is the distance on the compressor map between the operating point and the surge boundary. Maintaining margin means keeping the engine operating inside the stable region, away from the surge line. This is achieved by staying within the map, using bleed air to reduce the pressure rise and stabilize the flow, and scheduling—adjusting throttle/spool speed, fuel/air flow, and bleed schedules during transients—to prevent crossing toward the surge limit.

Compressor surge is a flow instability in which the compressor cannot sustain the required pressure rise at the current mass flow, causing the flow to reverse briefly through the stages and create large oscillations. The surge margin is the distance on the compressor map between the operating point and the surge boundary. Maintaining margin means keeping the engine operating inside the stable region, away from the surge line. This is achieved by staying within the map, using bleed air to reduce the pressure rise and stabilize the flow, and scheduling—adjusting throttle/spool speed, fuel/air flow, and bleed schedules during transients—to prevent crossing toward the surge limit.