Characterizing the Effects of Air Injection on Compressor Performance for Use in Active Control of Rotating Stall

Abstract

Previous work has developed an air injection controller for rotating stall based on the idea of a shifting compressor characteristic and the Moore-Greitzer three state compressor model. In order to demonstrate this form of control experimentally, a series of open loop tests were performed to measure the performance characteristics of a low speed axial flow compression system when air is injected upstream of the rotor face. The position of the air injection port relative to the hub and the rotor face and the angle relative to the mean axial flow were varied. The tests show that the injection of air has drastic effects on the stalling mass flow rate and on the size of the hysteresis loop associated with rotating stall. The stalling mass flow rate was decreased by 10% and the hysteresis loop was completely eliminated under some conditions. The results of the open loop parametric study were then used to implement a closed loop control strategy based on a shifting characteristic.