ACTIVE STABILIZATION OF ROTATING STALL IN A 3-STAGE AXIAL COMPRESSOR

A three-stage, low-speed axial research compressor has been actively s tabilized by damping low-amplitude circumferentially traveling waves, which can grow into rotating stall. Using a circumferential array of h ot- wire sensors, and an array of high-speed individually positioned c ontrol vanes as the actuator, the first and second spatial harmonics o f the compressor were stabilized down to a characteristic slope of 0.9 , yielding an 8 percent increase in operating flow range. Stabilizatio n of the third spatial harmonic did not alter the stalling flow coeffi cient. The actuators were also used open loop to determine the forced response behavior of the compressor. A system identification procedure applied to the forced response data then yielded the compressor trans fer function. The Moore-Greitzer two-dimensional stability model was m odified as suggested by the measurements to include the effect of blad e row time lags on the compressor dynamics. This modified Moore-Greitz er model was then used to predict both the open and closed-loop dynami c response of the compressor. The model predictions agreed closely wit h the experimental results. In particular, the model predicted both th e mass flow at stall without control and the design parameters needed by, and the range extension realized from, active control.