Influence of the Core Geometry of a Flat Torque Converter on Internal Flow and Loss

Passenger car torque converters have been designed with an increasingly lower profile in recent years for the purpose of achieving weight savings and a more compact size. However, flatter designs have tended to result in reduced hydrodynamic performance. The major cause of this performance deterioration is the pump, where relatively higher loss occurs at the core and suction surfaces. In this study, the internal flow characteristics of four torque converters having pump impeller passages with different contraction ratios were investigated numerically using a CFD code. The results show that there existed an optimum contraction ratio of the pump meridional passage in terms of efficiency. The four torque converters were then manufactured and tested in order to evaluate the change in their overall performance relative to the contraction ratio. The measured overall efficiency and visualized flow patterns tended to coincide well with the computation results.