The compressor exit Mach number control theory presented here will enable improved control of transient compressor working point trajectories of a turbine engine. This will allow the steady working line to be raised towards the surge boundary with the advantage of increased thrust and reduced specific fuel consumption. This new control method can replace the rigid acceleration and deceleration limiters of the fuel control loop, and achieve superior surge avoidance performance. This paper documents the theoretical and practical study of Mach number controllers designed for implementation with a simplified fuel pump system and the subsequent testing of the controllers on an aeroengine in the sea level test bed in DERA Pyestock. The new controller incorporated two Mach number dynamic limiting control loops (one each for acceleration and deceleration) besides the NH controller. Several designs were tested successfully and demonstrated not only Mach number control from idle to full power, but also surge avoidance. Engine start control was also tested in the latest engine test.

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