A Coupling Optimisation Strategy for Improving Flow Stability and Aerodynamic Performances of Turbocharger Centrifugal Compressors

Improving flow stability is one of the key tasks for turbocharger centrifugal compressors design, ported shroud casing treatment (PS-CT) is usually employed to enhance the flow stability, but it normally causes penalties to compressors' aerodynamic performances. The traditional optimisation methods of PS-CT cannot remove the penalties of aerodynamic performances while improving the flow stability. This study tries to resolve the problem by two steps. First, the design space of a turbocharger centrifugal compressor is extended to include both PS-CT and impeller-diffuser, this makes the optimal solution that can improve both flow stability, and aerodynamic performances physically exist. Second, based on the extended design space, a coupling optimisation method is developed for the compressor by integrating the random forest meta-model, the gradient mutation hybrid optimisation algorithm and the Sobol sensitivity analysis, making the optimal solution can be found and explainable. The results show that the coupling optimisation has successfully improved the compressor's aerodynamic performances over the whole characteristic curve while enhancing the flow stability. Specifically, the isentropic efficiencies at the design point and the near-stall point are raised by 0.90% and 2.90%; the stable operating range is extended by 9.94%. This is infeasible for the previous optimisations.