Numerical Analysis of Flow through High Pressure Ratio Centrifugal Compressor Impeller and Effect of Varying Diffuser Exit Width on Performance

Abstract

This paper carries out a comprehensive numerical investigation of turbocharger high-pressure ratio centrifugal compressor impeller. The aim is to study the effect of varying mass flow rate on the pressure ratio and efficiency from stall to choke using (3D) numerical simulations. The transonic SRV2 compressor developed by DLR (German Aerospace Center) has been used as the test case in this study. Numerical simulations have been performed using Reynolds Averaged Navier-Stokes (RANS) based k-ɛ model to predict turbulence. Y-plus is kept 35 for the structured mesh near the boundaries. In first part, calculations were carried out for design speed of 50,000 1/min to study the suitability of ANSYS CFX in the design procedure and compared the results with experimental data and four other (3D) solvers. The numerical simulations showed that ANSYS CFX over predicts the experimental data by 9% in this compressor. The second part describes the effect of vaneless diffuser exit width on performance parameters of centrifugal compressor at design high rotational speed, which shows that decreasing vaneless diffuser exit width increases pressure ratio, isentropic efficiency and operating range from stall to choke. Keywords— Centrifugal compressor, Diffuser Exit width, Numerical simulations, Entropy generation, Transonic, Pressure, Efficiency, Performance, Pressure ratio