Performance improvement and flow field investigation in hydraulic torque converter based on a new design of segmented blades

Abstract

Hydraulic torque converter is of lower efficiency in the powertrain, particularly at low speed ratio, which is crucial for vehicles due to its ability of torque multiplication. Therefore, torque converters should be taken into account with both higher start-up acceleration and transmission efficiency. Inspired by the fact that the multi-airfoils of the aircraft can improve the lift, a new design of segmented turbine blade in torque converter is presented to improve the transmission efficiency and start-up acceleration. To ensure reproducibility and popularization, the camber line and shape of blades are extracted to obtain the expression in the Cartesian coordinate system. A scale-resolving simulation setting, large eddy simulation with kinetic energy transport, and refined hexahedron meshes, which were verified by our studies, are applied to simulate the three-dimensional transient flow numerically. According to the results of computational fluid dynamics analysis, the new design eliminated the ultra-high vorticity of the near-wall boundary layer to reduce the flow loss, which further improves fuel economy. The pressure difference in the segmented turbine blade is significantly higher than that of the original model, causing the improvement of powertrain performance. As a result, the torque ratio and nominal torque increase by 6.7% and 7.7%, respectively, at stalling speed ratio; meanwhile, the maximum efficiency increases by 1.1%. This research, using a new design of segmented blades, has many advantages, such as high starting torque ratio, large adjusting range, and greater fuel economy, and shows great potential to apply in the manufacturing process.