Cm. Vanschalkwyk et al., ACTIVE STABILIZATION OF AXIAL COMPRESSORS WITH CIRCUMFERENTIAL INLET DISTORTION, Journal of turbomachinery, 120(3), 1998, pp. 431-439
This paper describes the first experimental validation of transfer fun
ction modeling and active stabilization for axial compressors with cir
cumferential inlet distortion. The inlet distortion experiments were c
arried our in a three-stage low-speed compressor. Theory-experiment co
mparisons of steady performance, unsteady stall precursor, and forced
response (transfer function) data were all used to assess a control-th
eoretic version of the Hynes-Greitzer distorted flow model. The tests
showed good agreement between theory and data and demonstrated that a
priori predictions, based on geometry and steady-state performance dat
a, can be used to design control laws that stabilize rotating stall wi
th inlet distortion. Based on these results, active feedback control h
as been used to stabilize the inlet distortion induced instability ass
ociated with rotating stall onset. The stabilization allowed stall-fre
e operation to be extended below the natural (distorted flow) stall po
int by lip to 3.7 percent for a 0.8 dynamic head distortion. For a 1.9
dynamic head distortion 40 percent of the mass flow range lost due to
inlet distortion was regained through active control. The paper eluci
dates the difficulties associated with active control with distortion,
and introduces a new control law that addresses many of these challen
ges.