【作者】 刘春宝；

【导师】 马文星；

【作者基本信息】 吉林大学 ， 机械设计及理论， 2009， 博士

【摘要】 本文结合浙江省科技厅重大科技专项项目“轿车扁平化液力变矩器研制”(2008C01036-4),基于三维流动理论及计算流体动力学(CFD)对轿车扁平化液力变矩器相关问题进行深入研究,在研究过程中定义更能反应整个循环圆形状变化的扁平率,设计环量变化更为合理的叶轮叶片,计算扁平变矩器性能,分析扁平率对扁平变矩器性能影响规律,提出扁平变矩器性能优化方法,目的是设计出性能优良、更好的满足车辆性能要求的扁平化液力变矩器。主要研究内容如下。1.提出新的扁平率定义和基于椭圆的扁平率循环圆设计方法,设计过流面积变化更为合理的不同扁平率的液力变矩器循环圆。针对不同叶轮叶片采用不同的二次函数环量分配规律进行设计,以得到叶形更为合理的不同扁平率的变矩器叶片。2.研究多流动区域耦合算法,主要有多运动参考系法、混合平面法和滑动网格法。针对液力变矩器多叶轮共同工作的特点,选择滑动网格法对轿车扁平液力变矩器瞬态复杂流场进行数值模拟。研究基于变矩器内流场数值解预测其性能的计算方法,并对变矩器进行台架实验,将计算得到的原始特性与实验结果进行了对比分析。3.深入分析不同扁平率液力变矩器内部流动结构及流场特性,研究不同扁平率下流场变化情况,对其流动结构和一些流动现象的成因进行分析。4.计算不同扁平率液力变矩器外特性和原始特性,分析不同扁平率下原始特性变化情况,总结扁平率变化对性能的影响规律。通过将泵轮叶片沿旋转方向由内环向外环倾斜的方法优化扁平液力变矩器性能,设计出性能满足车辆燃油经济性与动力性要求的扁平液力变矩器。更多还原

【Abstract】 The hydrodynamic torque converter is a kind of turbo machine which is widely used in today’s automatic transmissions for passenger cars. Its functions include damping of engine torque fluctuation, damping of noise and vibration in the drive line, and automatic amplification of torque according to the difference in rotational speed between the input and output shafts without requiring any external control. It also has great impact on the dynamical and fuel economy of passenger cars. Although the torque converter has existed for a century, there have been tremendous changes in the most recent decade. It has undergone continuous refinement through the years that have paralleled the development of the automobile, and these improvements continue. Most passenger cars with small and medium displacement engines have adopted a front-wheel-drive layout in recent years. Torque converters accordingly have been designed with an increasingly narrower profile for the purpose of achieving a smaller axial size, which also translates into weight savings. The research on the flat torque converter for the passenger car has been carried out early in abroad, but related research is in the blank in domestic. In this paper, the modern design method of the flat torque converter has been carried out for the purpose of developing better performance flat torque converter which could meet or exceed similar foreign products.1. Design of the flat torque converterThe shell is first determined in tradition design method of circulatory circle, and then, core and middle flow line are found out by means of flow section area. Using tradition design method often need modify several times to obtain satisfactory results. Tradition flatness ratio of the circulatory circle is defined as the ratio of the width to effective diameter that causes the change of the flatness ratio can’t completely reflect the change of the whole circulatory circle. To dissolve above two problems, considering the development of the CNC machining technology, the bran-new flat circulatory circle design method is put forward, and the shape is ellipse. Flatness ratio is defined as the ratio of short axial to length axial. So the better flat circulatory circle can be designed. By compared result of the new method with actual result, both of them have close magnitude and well agreement with. It shows that the new method is more correct and effective. The new method can be used in design of the flat circulatory circle. The three circulatory circles with different flatness ratio are designed by using new method.The blades of the torque converter are designed by momentum distribution method. The rules of momentum distribution decide blade shape, finally influence the performances of the torque converter. To find out the reasonable rule of the momentum distribution and get good blades, how the distribution affects the performances of torque converter is researched. The design method of the flat torque converter blade based on quadratic function distribution of momentum is put forward. Quadratic functions for each impeller are different to design better blades.2. Numerical simulation of the flow field and performances predictionWith the development of computer technology and Computational Fluid Dynamic (CFD) theory, numerical simulation of the torque converter flow field has been used in engineering practice. So the internal flow performances of the flat torque converters are investigated by numerical analysis using CFD software. Based on the numerical solution, the performances of the flat torque converter are predicted. As soon as figuring out the performances, the prediction results can be analyzed and compared with the test results. Then the correctness of numerical simulation of the flow field and performances prediction can be testify.Coupling algorithms for the multi-flow regions, which mainly include Multi Rotating Reference Frames model, Mixing Planes model, and Sliding Meshes model, its specific application in the hydrodynamic components are discussed. Sliding Meshes model is used in the numerical simulation of the unsteady flow field and which is transient method. Published available literature at home and abroad show that the transient calculation of unsteady flow field appears is first time.The control equations of the fluid mechanics are explained. For the incompressible viscous flow, the continuity equation and momentum equation are called as Navier-Stokes equations, short for N-S equations. Many turbulence models are established to make the equations closed. Among them, the RNG k ?εtwo-equation model is more precise, and the control equations include N-S equations and RNG k ?εturbulent equations. After comparison to different methods, such as, Finite Difference Method (FDM), Finite Element Method (FEM), Finite Volume Method (FVM), FVM is chosen to solve the equation. Up wind method is the way to accomplish the space discretion. SIMPLE method is used for coupling the pressure between continuity equation and momentum equation. The boundary conditions are such as‘grid interfaces’for interactive faces and‘wall’for others. The rotational velocity of each impeller is defined as same as the test to facilitate the performances comparison. The performances prediction method based on the numerical solution is also find out .The torque in each impeller of the torque converter D245 is figured out, then the performances is predicted. The results of performances prediction are analyzed and compared with the experimental results, both of them have close magnitude and well agreement. Then it comes to the conclusion the numerical simulation method and performances prediction for the flow field of the flat torque converter is correct and effective.3. Analysis of the transient flow fieldThe transient flow field of the flat torque converters which have different flatness ratio under speed ratio 0 and 0.81 conditions is investigated and analyzed for the purpose of learning the distribution rules of the pressure and velocity. The character of the flow field in pump, turbine and stator is analyzed in detail. At the same time, some statistical parameters are studied in depth. Through the analysis, several valuable conclusions are educed.4. Research on influence of the flatness ratio of the torque converter on hydrodynamic performanceBased on the analysis of internal flow field and numerical solution, the performances of the flat torque converters which are designed by both new and traditional torus design method are predicted. Then firstly, by comparing with the performances of the same flatness ratio torque converters designed by both new and traditional torus design method, it comes to the conclusion former is better. Next, by comparing with the performances of different flatness ratio torque converters designed by same method, the influence of the flatness ratio of torque converter on hydrodynamic performance is found out. Finally, the performances of the flat torque converter are advanced by changing the structure parameters, the results of characteristics prediction are compared with that of original torque converter. It shows that the performances of optimization torque converter are significantly improved.更多还原