| The automotive torque converter directly connects the engine to the transmission shaft and hence any performance improvement of the converter can significantly have influence on the car performance. In order to improve the converter performance, a detailed understanding of the internal flow structure and its effect on the key performance parameters is essential. Previous researches adopted too many simplified models. 1-D and 2-D theoretical methods were often applied. Now it's not easy to have experimental investigation on the inner flow. In recent years CFD studies are reported to be effective in the field. So, the internal flow fields of W305 torque converter used in certain military vehicles were calculated by CFD. The flow fields are interpreted for future improvement and the overall performances of the converter were calculated from the flow data. There are five chapters in this paper. In the first chapter, the project background is introduced. Numerical studies on the torque converter can be practically used to improve the torque converter performance. Computational studies in the fields are introduced. Main experimental methods of flow fields are introduced briefly. At last, the meaning and purpose of this paper are given. In the second chapter, Basic control equations of CFD are provided. Main 3-D torrent models are systematically introduced. Their features are analyzed. Numerical method structures are provided. Several numerical methods are compared. Basic theory of finite volume method used in STAR-CD, discrete solutions, and velocity-pressure coupling methods are introduced. Theoretical Basics are laid for STAR-CD applications. The main contents of the third chapter are to build computational modes of flow passages and provide boundary conditions. Firstly, Assumptions of torque converter flow fields are made. 3-D models of flow passages are made by UG.. These models are imported to ICEM-CFD for grid generations. In order to choose most suitable models and numerical solutions, different samples are set. The results are compared. k ?εTurbulence models, SIMPLE algorithms and Upwind Differencing (UD) scheme are chosen. Suppose the inlet boundary condition of the flow passage is velocity, and suppose outlet is pressure boundary condition, and suppose others are No-slip wall boundary condition. In the end the boundary condition values are provided. The convergence principles are set as the numerical ending standards. A flow chart is used to describe the flow calculation process. In this paper steady state simulations were performed for a range of speed ratios from 0.0 to 0.8 while maintaining an impeller speed of 2500 rpm. In the forth chapter, the numerical calculation and experimental results of the overall performance of the torque converter are compared. The flow data are interpreted and compared with those obtained experimentally. The followings are conclusions: In the numerical studies on torque converters, SMPLE algorithm has better convergence and is steadier, with satisfied accuracy. High-order discrete schemes can not improve accuracy in great degree. One order discrete scheme can have satisfied accuracy and steady state. Compared with overall performance experimental results, numerical results of commercial software STAR-CD are effective. The use of STAR-CD reduces the development time of torque converter. Great scope of circulation appears in the inside of the pump passage, and reverse flow appear on the working face around the inlet. the shell and the working face appear off flow, so does the intersect of the shell and the non-working face appear around the outlet. The phenomenon is mainly caused by the impact of the flow to the non-working face on the pump inlet in the inside of the pump passage. At the low velocity ratio, there are off flow and circulation. in the front part of the turbine passage,and large velocity grads on the section of the flow. In the condition of the most efficiency, velocity distributions are equality on the section of the flow. Only a low velocity section in the front part of the flow where curvature changes largely and no off flow and circulation. The outlet flow is equality and steady. The flow character in the turbine is mainly for the shape of the turbine passage. In the front part of the flow curvature largely changes, so the flow character is complex. The outlet of the flow has short curve, so the flow is steady. the stator flow passage is short and the angle largely changes ,so it can change...
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