Unsteady aerodynamic response of the rotor blades of an axial flow compressor operating under conditions of circumferential inlet distortions and rotating stall

Abstract

The aim of this work is to study the unsteady response of rotor blades of a lightly loaded single stage axial flow compressor experiencing inlet flow distortions in forms of circumferential pressure distortions and rotating stall . Recent developments in pressure transducer and microprocessor technology have enabled the research scientist to study the aerodynamic behaviour of rotor blades . Two rotor blades of the axial flow compressor have been instrumented with sixteen miniature pressure transducers , eight of which are on the pressure surface of one of the blades , while the remaining eight are on the suction surface of the other blade . An on-line microprocessor based data acquisition system has been developed to record simultaneously , measurements from each blade . Four different circumferential wire mesh screens of different extents and densities were employed at a distance of one chord length upstream from the blade leading edge to generate circumferential square wave pressure distortions . Also the compressor was run under conditions in the rotating stall regime . Flow parameters ahead of the rotor have been measured by using high response 3-hole cylindrical probes and a conventional 3-hole wedge probe . The values of the dynamic normal force coefficient were derived from instantaneous wall static pressure measurements on the two blade surfaces . The results obtained from the experiments were compared with the theoretical predictions.