Test and analysis of internal flow field in turbine of hydrodynamic torque converter based on particle image velocimetry

Abstract: The hydrodynamic torque converter is a major component of an automatic transmission. It transfers power from the engine to the transmission gearing system. The hydrodynamic torque converter has been applied in numerous automatic transmissions such as passenger cars, trucks, buses and trains. The external performance of hydrodynamic torque converter is affected by its internal flow characteristics. In order to study the internal flow characteristics of hydrodynamic torque converter, the internal flow field of hydrodynamic torque converter was tested based on particle image velocimetry (PIV) technology. As a powerful optical technique, instantaneous measurement of flow velocity at several positions in a plane can be tested by PIV. Instead of measuring at only one point in the flow field, such as laser doppler velocimetry and hot-wire anemometer, PIV has the ability to capture the spatial velocity distribution for a whole field simultaneously with high resolution. The technique is non-intrusive and no probe disturbs the flow. These features have made PIV a very useful technique in the characterization of unsteady and turbulent flow fields. PIV measurement can be performed in combination with other optical measurement methods to increase the understanding of complex phenomena. In order to capture high-quality flow images, hydrodynamic torque converter of transparent type was manufactured in imitation of the actual hydrodynamic torque converter, and plexiglass was chosen as the manufacturing material. In order to improve the transparency of experimental prototype, surface polishing was carried out several times. Aluminium powder was chosen as tracer particle, and distilled water was chosen as flowing medium. High speed camera was applied to capture flow images with different particle diameters and different particle concentrations under different working conditions. The shooting speed of charge-coupled device (CCD) was 1 000 frames per second. The velocity field and vorticity field of radial section in turbine were acquired through images preprocessing and cross-correlation calculation of 2 successive frames. A contrastive analysis of flow field distribution and complex flow phenomenon in flow area was done. It was found that flow parameters recognized and extracted in flow area were much richer when the concentration of particles was higher (2.4 g particles input to 1 500 ml distilled water) and the diameter of particles was smaller (10 μm). At this time, the information of velocity field and vorticity field was more reliable. Complex flow phenomena, such as multi-scale vortex and reverse flow, were caused because of distribution structure of high-gradient flow field and inhomogeneous distribution of velocity field. And also, the energy loss of internal flow in hydrodynamic torque converter was caused. As the speed ratio increased, the structure of internal flow field became more disciplinary and the energy loss became lower. It has important engineering significance for structure optimization and performance improvement of hydrodynamic torque converter through the analysis of experimental measurement results.