Influence of volute distortion on the performance of turbocharger centrifugal compressor with vane diffuser

As the geometry of the volute of turbocharger compressor is non-axisymmetric, it causes a distortion at the outlet of the diffuser and influences the upstream components. A distortion model in which a pressure distortion was applied as outlet boundary condition was established to simulate the distortion induced by the volute. It turned out to be sufficient to impose a circumferentially asymmetric pressure distribution at the outlet of the diffuser to replace the volute. Based on the distortion model which was verified, the influence of the amplitude of the distortion on the performance of centrifugal compressor was studied in detail. The results show that the distortion severely harms aerodynamic stability of the investigated compressor. The larger the amplitude of the distortion, the worse the performance of the compressor. The distortion induced by asymmetric volute propagates to upstream components and causes local flow separation at part of diffuser and impeller, and then causes the compressor surge. When the amplitude of the volute distortion is 10%, the stable flow range of the centrifugal compressor decreases to near zero. To authors' knowledge, the relationship between the compressor performance and distortion amplitude is first obtained quantitatively, which provides evidence to improve the performance of turbocharger compressor by decreasing the distortion induced by asymmetric volute.