Hydraulic Design Optimization of a Torque Converter



The client is one the leading manufacturers of torque converter in automotive industry. In this project they asked ADT to perform a hydrodynamic design optimisation of a torque converter using the inverse design code TURBOdesign1.

The design objectives were to minimise the hydrodynamic loss generation in all components of the torque converter, i.e. pump, turbine and stator.


Fig. 1. Flow in the Torque Converter


The design targets were to improve the hydraulic performance of the torque converter and reduce its power consumption at various speed ratios.

The client provided ADT with the geometry of the existing torque converter and its operating conditions. ADT performed a CFD simulation in one flow channel through the torque converter. CFD results indicated that there was a clear mismatch between adjacent blade rows at the operating speed ratio which results in very high incidence on the turbine and stator blades and consequently large flow separation regions occurred in the stator and turbine channels.

Redesign of all three components of the torque converter was then performed using TURBOdesign1, including both the meridional shape and blade shape. Each component was individually designed, however the effect of the upstream conditions were accurately simulated in TURBOdesign1 by extracting the outflow condition of one component and applying it as the inflow boundary condition of the subsequent component.

By redesigning the geometries of three components of the torque converter i.e., pump, turbine and stator, we have seen up to 12% reduction in torque converter power consumption at design speed ratio and significant improvement at off-design.

TURBOdesign1 also allows for a non uniform (non-free vortex) specification of spanwise work distribution for each component. This feature was used effectively to reduce the blade loading near the core and increase it near the shell of the converter, as the blades near the core have a much smaller chord length comparing to the shell.



CFD analysis of the redesigned torque converter shows an increase of about 4% in the flow rate through the machine due to improvement in the hydraulic performance and 12% reduction in the overall converter power consumption. Figure 1 shows the flow streamline in the pump, turbine and stator of the redesigned torque converter.



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