Experimental investigations on effects of the self-circulation casing treatment on acoustic and surge characteristics in a centrifugal compressor

Self-recirculation casing treatment is an effective technique to improve centrifugal compressor surge margin. This paper experimentally investigates the impacts of casing treatment on a centrifugal compressor using experimental methods and focuses on aerodynamic performance, surge trigger, surge cycles, and inlet acoustic characteristics. The measuring data were obtained from fast dynamic pressure transducer and microphones, and temporarily and spectrally analyzed to show surge inception and noise variation. The experimental results lead to the conclusions that (1) two separate phenomena trigger compressor to surge with different surge frequencies in the compressor with and without the casing treatment, and (2) the casing treatment suppresses the broadband noise sources but enhances the discrete frequency noise sources during surge cycles.