By means of pseudo lumped-blade simulation method (PLSM), the blade torque vibration in the torque converter under different speed ratios is extracted and analyzed. The result indicates that the wheel torque pulsation is induced by flow fluctuation, while the mechanism of this flow fluctuation lies in the continuous switch of the blade position of pump and turbine related to the stator.

There are mainly two states for stator flow channel: “pass” and “block”. In the “pass” state, the upstream flow channel is aligned to the downstream inlet. Besides, due to the influence of the wake transmitted from the upstream wheel and the vortex vortex arisen from the suction surface of the blade, the blade torque would be relatively larger in the “pass” state. The successively switch between the two states leads to the fluctuations of the blade torque, so as to its wheel torque, which which is the sum of all blade torques. However, due to the inconsistent relative position of the different wheel blades, the “offset” effect leads to the fact that the fluctuation of wheel torque is much smaller than that of the blade torque. In addition, by applying FFT transformation on the transient torque data, the frequency distribution of the blade surface pressure is obtained. It was found that rotation frequencies and interaction frequencies with both upstream and downstream components are significant, and the dominant frequency is always the interaction frequency at different speed ratio, which reveals that the successively switch of the turbine blade position related to stator are the main cause of its flow induced vibration, and this vibration can be transmitted downstream the flow channel, and affect the flow field of other components downstream.

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