Stability Improvement of Turbocharger Centrifugal Compressor by Asymmetric Vaneless Diffuser Treatment

The asymmetric flow field induced by the volute has considerable influence on the performance of a turbocharger centrifugal compressor, especially through its effect on the stability. In this paper, a novel asymmetric vaneless diffuser treatment with a circumferentially non-axisymmetric diffuser width distribution was firstly developed to enhance the stability of a centrifugal compressor for turbocharger. Design principle of the asymmetric diffuser was proposed based on the asymmetric flow in the compressor. The objective of the asymmetric vaneless diffuser design is to alleviate the flow asymmetry in the diffuser, which requires that the phase of the maximal diffuser width is coincident with the phase of the minimum static pressure in the diffuser. The results of the numerical simulation showed that the designed asymmetric diffuser was able to decrease the magnitude of the pressure distortion induced by the volute and therefore alleviated the negative effect of the volute on compressor stability. Experimental results showed that the designed asymmetric diffuser extended the stable flow range by 28.3% at designed speed compared to the prototype with symmetric diffuser.