What is compressor surge and stall, and how are they prevented?

Compressor stall occurs when blade angle of attack exceeds the stall limit, causing local flow separation and reduced compression. Surge is a global instability where the entire compressor flow reverses momentarily, causing loud bangs and potential damage. Causes include rapid throttle changes, inlet distortion, foreign object ingestion, and operating at extreme conditions. Prevention methods: Variable stator vanes adjust flow angles across operating range, Bleed valves dump excess air at low speeds, Inlet guide vanes control flow direction, Surge margin maintained through control laws, and Multi-spool designs allow shafts to operate at independent optimal speeds.