Experimental Study on Flow in a Supersonic Centrifugal Impeller

Abstract

An impeller of a supersonic centrifugal compressor was tested in a casing without a diffuser so that the flow range was not limited by the diffuser. Regarding the impeller, emphasis was placed on critical conditions such as inducer stall and surge. Experimental data were examined based on a one-dimensional analysis and a quasi-three-dimensional analysis. Furthermore, the variation of shroud pressure with respect to time at many locations was utilized to guess the details of flow behavior between impeller blades near the shroud, and the contour of isobars was compared with that predicted by a quasi-three-dimensional analysis. When the inlet relative velocity was supersonic, a detached shock wave and a shock wave in a blade channel were recognized, but the compressor operated efficiently, although such condition existed only in a narrow flow range limited by surge and choke.