Rotor-stator aerodynamic interaction of centrifugal compressor at pulsating backpressure conditions

Abstract

The performance of a centrifugal compressor is strongly influenced by pulsating backpressure condition, but little knowledge of the mechanism has been obtained. This study investigates aerodynamic interaction between impeller and volute at pulsating condition via experimentally validated numerical method. Results show that the features of volute-induce distortion at impeller exit are closely coupled with pulsating backpressure at different operational conditions. Specifically, the volute-induce pressure distortion varies out-of-phase with the mass flow rate near surge condition (OP2), but in phase near choke condition (OP1). The circumferential flow distortion at the impeller outlet manifests a notably unsteady effect at pulsating conditions for both OP1 and OP2. Comparing with the quasi-steady cases, the magnitude of the distortion is alleviated maximally by 2.3% and 2.7% for OP1 and OP2, respectively. The evolution of secondary flow patterns in the impeller show that an array of vortex tubes appears in the shroud region of the inducer downstream the main blade leading edge. It is resulted from the rolling-up of vortex sheet due to the K-H instability. The pulsating backpressure can profoundly depress the development of the vortex street. Therefore, the blockage effect by the vortex street in the inducer is alleviated.