Stress-blended eddy simulation and visualization validation of unsteady viscous oil cavitation in hydrodynamic torque converter

As hydrodynamic torque converter developing towards higher power density, leading to severe cavitation in the internal viscous oil, which adversely impacts performance and energy efficiency. This study introduces a novel borescope observation technology for visualizing cavitation in hydrodynamic torque converter. Utilizing this visualization approach alongside numerical calculation method, the research investigates transient cavitation phenomena within the torque converter, with a particular focus on the stator flow field. The development of a stress blended eddy simulation model for cavitation flow allows for an in-depth examination of the interaction between cavitation and vortex within the 3D enclosed flow field, elucidating the transient mass transfer process. Visualization successfully captures attached cavitation at the stator blade leading edge revealing a decrease in cavitation extent with increasing speed ratio. CFD simulations incorporating cavitation accurately predict the hydrodynamic performance, highlighting the significant impact of cavitation on performance metrics such as capacity factor and torque ratio. Identifying the critical cavitation number for torque converter underscores the adverse effects of cavitation on performance below this threshold. This comprehensive analysis, combining visualization and simulation, offers valuable insights into cavitation dynamics within hydrodynamic torque converter, laying a foundation for further optimization of flow mechanisms and performance improvement.