Effect of inlet strut length on the stalling characteristics of an axial-flow compressor

Abstract

A low-speed single-stage axial-flow compressor rig was configured for tests with variable-length upstream casing struts. Two axial strut lengths were tested for their effect on the inlet flow field and stalling characteristics of the compressor under clean and distorted inlet conditions. Data were obtained from one stationary and six blade-mounted high-response pressure transducers, and from a circumferentially- traversed directional probe. The distorted inlet flow field was changed significantly by the longer struts, which effectively sectored the inlet. Deep stall was not observed for this configuration. Rather, the stalling characteristic was changed to what is termed progressive rotating stall, in which six stable stall cells and significant increases in static pressure rise were noted. A new technique for determining the number of rotating stall cells from the frequency content of stationary and rotating reference frame signals is presented. Blade pressure response as a function of aerodynamic loading is detailed.