Research on Effect of Endwall Contouring of Vane Diffuser on Stable Operating Range of Centrifugal Compressor

Abstract

Abstract The present investigation seeks to comprehensively analyze the impact of diverse endwall contouring strategies on the operational stability of a singular high-pressure ratio centrifugal compressor stage. Employing numerical simulation techniques, this study systematically examines the implications of contoured wall positions, specifically convex profiles at the pressure side and/or concave profiles at the suction side, as well as asymmetric endwall contouring, on both performance metrics and internal flow dynamics within the centrifugal compressor stage. And the stability enhancement mechanism of endwall contouring is clarified. The results demonstrate that employing full circular contoured vaned diffusers on the hub-side wall can achieve a maximum improvement in stall margin of 15.10%. Additionally, the diffuser featuring solely convex profiles at the pressure side on the hub-side wall exhibits an augmented stall margin by 8.39%, coupled with a reduction in performance loss at low flow rate conditions. The application of an asymmetric endwall contouring scheme improves stall margin by 8.39%, and mitigates the performance loss across the entire operating range. At the near-stall point, the contoured endwalls redirect fluid towards the suction side, thereby mitigating the incidence at the vane leading edge and attenuating the interaction between the impeller trailing edge vortex and the diffuser leading edge vortex. Moreover, concave profiles at the suction side serve to accelerate the fluid on the suction side along the flow direction, thereby suppressing the corner separation to weaken the passage blockages. Simultaneously, contoured endwall increases the negative static pressure rise within the flow channel away from the volute tongue. The advantages of endwall contouring in vane diffusers extend to the improvement in the circumferential nonuniformity of flow fields and the enhancement in diffuser stability. Consequently, this research lays the foundation for optimizing the flow control method of endwall contouring on the centrifugal compressor.