Effects of pump blade cutting on the performance of a hydraulic torque converter

This study aims to investigate the impact of different cutting schemes on the internal flow field and external characteristics of the impeller blade in the hydraulic torque converter pump. A systematic analysis was carried out to explore the evolution of vortex structure and energy conversion. The internal flow field was also numerically simulated in the automotive punch-welded hydraulic torque converter under different cutting schemes using computational fluid dynamics and stress-blended eddy simulation (SBES). The accuracy of the simulation was verified using external characteristic experiments. A full channel model was established after that. The weights of blades were cut by 10%, 20%, and 30% than before in the hydraulic torque converter pump. The optimal threshold was selected to reconstruct the three-dimensional vortex structure using Q-criterion vortex identification. The feature extraction was also performed on the internal three-dimensional vortex structure in the pump wheel flow channel under different cut schemes. The multi-scale vortex dynamics were qualitatively analyzed in this case. The two-dimensional flow field was intercepted at different spatial positions. The flow map was then quantitatively extracted from the flow velocity field, in order to reveal the spatiotemporal evolution of the multi-scale flow field. Qualitative and quantitative interactive analysis was used to clarify the influence of the cut degree of the pump impeller blade on the internal/external characteristics of the hydraulic torque converter. The results show that the torque ratio of the pump impeller blade gradually increased after three cuts of 10%, 20%, and 30% on the pump impeller blade, particularly from 1.77 of the prototype hydraulic torque converter to 2.33 of the 30% cutting. By contrast, the torque coefficient of the pump wheel significantly decreased, from 5.51 of the prototype torque converter to 3.39 of the 30% cutting. Once the pump impeller blade was cut by 10%, the torque ratio of the hydraulic torque converter only increased by 4.34%, but the torque coefficient of the pump decreased by 10.73%. A better performance was achieved to reduce the torque coefficient of the pump. When the pump blade was cut by 20% and 30%, the torque ratio of the hydraulic torque converter increased by 16.78%, and 7.81%, respectively, whereas, the torque coefficient of the pump decreased by 18.88% and 15.08%, respectively. Furthermore, the area and thrust of pump impeller blades, and the kinetic energy of the fluid decreased, as the cutting degree of pump impeller blades increased, indicating the weak trend of multi-scale vortex motion. Some changes were found in the vortex structure in the middle of the flow channel, with the gradual weak merging of multi-scale vortices. There was also the weak high-energy small-scale vortex shedding at the outlet of the pump impeller flow channel. In the two-dimensional flow field, the outlet velocity of the impeller channel decreased with the increase of blade cutting degree, from 23 m/s in the prototype to 19 m/s in the impeller blade cutting of 30%. The inlet flow velocity of the pump impeller channel remained basically unchanged, while there was the slight reduction in the high and low flow velocity area at the turbine channel inlet. The low flow velocity area of the suction surface was reduced in the stator, where the average flow velocity decreased from 22 m/s of the prototype to 16 m/s when the pump impeller blade was cut by 30%. The flow velocity of the channel changed significantly under blade cutting, resulting in a decrease in the torque coefficient of the pump impeller. This finding can provide some guiding suggestions for the design and performance optimization of hydraulic torque converter blades.