Abstract: Taking a low-speed axial contra-rotating compressor as the research object, a high frequency dynamic pressure sensor array arranged at the tip of the front and rear rotor is utilized to capture the stall initiation disturbance characteristics under different speed configurations and distortion conditions. The results obtained by analyzing the pressure waves collected at stall condition show that the stall type at the design speed is rotating stall when the inlet flow is uniform, and the propagation direction is consistent with the rear rotor rotation direction The maturely developed stall is fixed at a circumferential position and does not rotate circumferentially when the speed ratio is 1.40. With further increase in the front and rear rotor speed difference, the type of stall disturbance at speed ratio of 1.52 changes again to rotating stall. But the stall disturbance propagates in the same direction as the front rotor rotation due to the reduced suction effect of the rear rotor on the front rotor wake. The stall disturbance characteristics at different speed ratios are all consistent with a uniform inlet when the compressor incoming flow is changed to be circumferential inlet distortion. However, the distortion will cause different amplitude fluctuations in the pre-stall pressure sequence at different circumferential positions. The empirical mode decomposition-local mean de-composition (EMD-LMD) method is employed to capture the small pre-stall perturbations that gradually accumulate energy over time.

Key words: contra- rotating compressor, experiment, speed ratio, inlet distortion, stall type