An Experimental Investigation of Unsteady Flow from Interaction between Impeller and Diffuser on Centrifugal Compressor

Abstract

Flow measurements, hot wire and pressure patch, were taken in an unshrouded centrifugal impeller to investigate the effects of impeller-diffuser aerodynamic interaction on the flow field. Experiments were carried out using three different diffusers, vaneless diffuser, vaned diffuser with 1% radial gap, and 5%, for three different flow rates corresponding to near stall angle, nearly zero incidence angle and negative angle. The tip leakage vortex on the casing wall was discharged from radial to circumferential, as the flow rate was reduced. At the inlet of diffuser for the near stall flow rate, the wake region spreaded over the casing wall near the suction surface, especially when the impeller blade was close circumferentially to the diffuser.