Increasing Pulse Energy Recovery of Radial Turbocharger Turbines by 3D Inverse Design Method

Abstract

Most radial turbines have a peak efficiency at around U/Cis (velocity ratio or jet speed ratio) of 0.7. It is a well-known fact that it is beneficial for radial turbocharger turbines to have a higher efficiency at low U/Cis region, since the pulsating engine exhaust gas at low U/Cis region (with high pressure and temperature) carries more energy compared to that at high U/Cis region (with low pressure and temperature). The improvement of Total to Static efficiency at low U/Cis region will help the turbine extract more energy from the exhaust gas and thereby increase the turbine cycle-averaged Total to Static efficiency. In the past there has been some attempts to move the peak U/Cis to lower values by using conventional or direct design approach on mixed flow impellers. But this approach usually results in reduction of stage performance. In this paper, a methodology is presented to control and move the radial turbine peak efficiency U/Cis to lower values by using a 3D inverse design method. The stage performance is measured by using steady CFD analysis. Furthermore detailed stress and vibration analysis are presented on the mechanical performance of the new design.