Performance and stalling behavior of an axial-flow compressor subjected to three circumferential inlet distortion levels

Abstract

The performance and stalling behavior of an axial-flow compressor subjected to several different inlet distortion patterns was investigated. The effect of inlet distortion on overall compressor performance was determined through the measurement of compressor characteristics for each inlet flow condition. Dynamic pressure transducers were employed to investigate rotating stall cell behavior during the inception of stall. Rotor blade response to distorted inflow was measured in the form of average blade pressure profiles by using a scanning valve. Results indicated a substantial reduction in total pressure rise capability for distorted operation. A 25 per cent loss in stall pressure rise was observed for the most severe distortion level. The stall cell was found to rotate in the direction of rotor motion, but at one-half the rotor speed. The cell encompassed the rotor blade tip region down to approximately midspan. During the onset of stall, the circumferential extent of the cell was observed to vary from 60 to 80 degrees. At the rotor blade tip the stall cell relative pressure fluctuations indicated zero flow through the cell. The amplitude of the stall cell was attenuated in the distorted flow region due to the lower air velocity behind the distortion screens. Rotor blade suction side pressure measurements indicated that increasing the circumferential extent of distortion above some "critical" value induced blade stall at higher flow rates. For the low speed compressor used, it appears that the critical angle phenomena is a function of compressor design and is independent of distortion level.