Integrated control of rotating stall and surge in aeroengines

Aeroengines operate in regimes for which both rotating stall and surge impose low flow operability limits. Thus, active control strategies designed to enhance operability of aeroengines must address both rotating stall and surge as well as their interaction. In this paper, a nonlinear control strategy is designed based on an analytical model to achieve simultaneous active control of rotating stall and surge in an axial flow compression system with relevant dynamics representative of modern aeroengines. The controller is experimentally validated on a 3-stage low-speed axial flow compression system. This rig is dynamically scaled to replicate the interaction between rotating stall and surge typical of modern aeroengines, and several experimental results are presented for this rig. For actuation, the control stategy utilizes a single plenum bleed valve with bandwidth on the order of the rotor frequency. For sensing, measurements of the circumferential asymmetry and annulus-averaged unsteadiness of the flow through the compressor are used. Experimental validation of simultaneous control of rotating stall and surge with minimal sensing and actuation requirements is viewed as an important step towards applying active control to enhance operability of compression systems in modern aeroengines.