Cavitation simulation of automotive torque converter using a homogeneous cavitation model

To understand the flow mechanism of cavitation and its effect on the performance of automotive torque converter, numerical simulation considering cavitation is carried out at various turbine-pump speed ratios from 0 to 0.8. Since the cavitation in working fluid of torque converter is rather gaseous than vaporous, the partial pressure of air is applied to the cavity pressure in the simplified Rayleigh Plesset cavitation model used in the present simulations. It is found that, for the lower speed ratios (<0.4), the cavitation starts to occur firstly at the stator with the decrease of the ambient pressure, which seems to significantly block the stator passage. The mass flow circulating in the torque converter gradually decreases, which results in the gradual decrease of the pump torque. On the other hand, for the higher speed ratios (>0.6), the cavitation occurs at the pump inlet simultaneously or earlier than that at the stator. Once the cavitation occurs at the pump, the pump torque seems to drop suddenly.