In a dual-spool compressor, the low speed compressor seeks...

In a dual-spool compressor, the low speed compressor seeks...

• A. Its own best operating speed
• B. The engine idle speed
• C. The high-speed compressor speed
• D. Maximum thrust speed

Answer: (A)

In a dual-spool engine, each compressor (low-pressure and high-pressure) has its own performance map and speed range. The control system aims to operate the low-pressure compressor at its own best operating speed—the point on its map where it can deliver the required pressure rise with the highest efficiency and adequate surge margin for the current flow and turbine speeds. This separation lets the two spools interact to meet thrust demands without one being forced to follow the other’s speed, which would reduce efficiency and risk instability. Chasing the high-speed compressor’s speed or running at idle or maximum thrust would pull the low-pressure stage away from its optimal point, increasing fuel use and the chance of surge. So the low-speed compressor seeks its own best operating speed.

In a dual-spool engine, each compressor (low-pressure and high-pressure) has its own performance map and speed range. The control system aims to operate the low-pressure compressor at its own best operating speed—the point on its map where it can deliver the required pressure rise with the highest efficiency and adequate surge margin for the current flow and turbine speeds. This separation lets the two spools interact to meet thrust demands without one being forced to follow the other’s speed, which would reduce efficiency and risk instability. Chasing the high-speed compressor’s speed or running at idle or maximum thrust would pull the low-pressure stage away from its optimal point, increasing fuel use and the chance of surge. So the low-speed compressor seeks its own best operating speed.