Active Control of Rotating Stall in a Low Speed Axial Compressor

The onset of rotating stall has been delayed in a low speed, single-stage, axial research compressor using active feedback control. Control was implemented using a circumferential array of hot wires to sense rotating waves of axial velocity upstream of the compressor. Circumferentially travelling waves were then generated with appropriate phase and amplitude by “wiggling” inlet guide vanes driven by individual actuators. The control scheme considered the wave pattern in terms of the individual spatial Fourier components. A simple proportional control law was implemented for each harmonic. Control of the first spatial harmonic yielded an 11% decrease in the stalling mass flow, while control of the first and second harmonics together reduced the stalling mass flow by 20%. The control system was also used to measure die sine wave response of the compressor, which behaved as would be expected for a second order system.