Effects of volute’s asymmetry on the performance of a turbocharger centrifugal compressor

The effects of the volute’s asymmetry on the performance of a turbocharger centrifugal compressor were studied using steady simulations and theoretical analysis. According to the steady simulation results, it is found that the volute’s asymmetry has significant influence on the performance of the centrifugal compressor. The variation of the stage efficiency due to volute’s asymmetry is up to 4%. Meanwhile, the volute’s asymmetry restricts the compressor stable flow range by imposing a distorted outlet pressure condition and forcing some certain impeller passages to suffer from a worse flow than the others. These certain passages are likely to stall first and trigger the surge, as the stage flow rate further decreases. In other words, the local stall triggers the surge. The relevant flow mechanisms were given to explain the effects based on the three-dimensional flow field, and a new model was developed to demonstrate how the local stall induced by the volute’s asymmetry triggers the system instability.