Influence of the Flatness Ratio of an Automotive Torque Converter on Hydrodynamic Performance

Abstract

Automotive torque converters have recently been designed with an increasingly narrower profile for the purpose of achieving a smaller axial size, which also translates into weight savings. Four torque converters with different flatness ratios were manufactured and tested in order to evaluate the change in their overall performance, including efficiency, stall torque ratio and torque transmission capacity. The experimental results show that the overall performance deteriorates when the flatness ratio is reduced to less than about 0.2. The internal flow characteristics of the torque converters were also investigated by numerical analysis using a CFD code. The computational results indicate that the main cause of this performance deterioration is a reduction in pump efficiency, which is attributed to increases in shock loss in the inlet region, separation loss in the fore half region, and friction loss in the exit region.