Effects of noise, magnitude saturation, and rate limits on rotating stall control

Operability enhancement is one of the major goals for active control of rotating stall and surge in axial compression systems. Using a reduced order model derived by Moore and Greitzer (1986), we show that the operability enhancement achieved by bleed valve actuation is seriously limited by fluid noise, and actuator magnitude and rate limits. By approximating the attracting saddle-sink connections, we reduce the 4D model to a 2D system. Algebraic formulas relating the operability enhancement to the actuator limits, the fluid noise, and the shape of the compressor characteristic are obtained by approximating the stable manifold of a saddle fixed point for the reduced system. Finally, the reduction and approximation techniques are shown to be viable by numerical simulations for a model of a low speed rig with a fast valve and a slow valve.