| With the development of computers,fluid mechanics and various fluid dynamics analysis software (CFD) techinology in recent years, At the same time, the cognition of flow field is the core of modern design methods in torque converter , it effects the performance of forecast analysis directly, it is the theoretical foundation of improving comprehensive-performance of torque converter and reducing R & D cycle. according to the requirements of national defense-research project "light off-road vehicle traction control technology", take W305 torque converter in "TC + AMT"system as prototype,reasearching on internal flow optimization technology,take staring condition as example,making a preliminary study on optimization method of the pressure difference between inlet and outlet by using Sculptor. Following five parts are main contents.1. Describing the surrounding of the project and explainning that numerical investigation is an important way to make research on the internal flow of the torque convert and improve the performance. Then, introduce the working principle of torque converter and status on domestic and overseas research and developing tendency.2. Introduced the basic theory of computational fluid dynamics, so as to have knowledge of the basic principles of software FLUENT and lay a theoretical foundation for later analysis by using FLUENT. First, the continuity equation and the basic fluid dynamics equations-N-S equation is derived by three fluid conservation equations, and then discussed the turbulence simulation model and the characteristics of these models; put key focus on k–εmodel which is suitable for torque converter. Following this, introduced the unified form control equation and derived out that Control equation is special form of convection - diffusion equation on the unity of the form of equations. Finite volume method is popular for solving convection - diffusion equation. Adopting velocity-pressure couple algorithm for solving the pressure between continuity equation and momentum equation, which contains two different kinds of strategies , PISO and SIMPLE.Compared the two different algorithms ,choosing later.3. Building calculation model of flow passage and define boundary conditions. Introduced the basic program structure and characteristics of software FLUENT, and then put forward some assumptions to the flow of torque converter to simplified the flow field. On the basis of this, divided the numerical simulation of the torque converter into three parts, pre-treatment, solution calculator , post-processing. pre-treatment contains building model,how to choosing flow passage, mesh dividing and setting boundary conditions.At the beginning, establish the three-dimension model of the flow passage with UG software and put it into the GAMBIT for mesh dividing, then define boundary conditions. Suppose the inlet boundary of the flow way to velocity boundary condition, and outlet to pressure boundary condition, no-blade surface as periodic conditions and and other to wall boundary, mixing plane has been used between neighbor zones. Solving calculator is choosing the algorithm, turbulence model, and the initial conditions of and the convergence criteria for solving N-S equations.Post-processing is that selected several cross-sections for analysis after simulation.4. Making relatively comprehensive analysis to the start situation (velocity ratio i = 0 ) ,(velocity ratio i=0.4) and the most efficiency situation(velocity ratio i=0.8)and conclude that:The pressure distribution in the pitch plane is becoming more proportional to the radius with the rising speed ratio in pump. Since the shock of entrance flow, there are strong secondary flow field in the section of inlet and shell, and at the beginning, the direction of flow is to pressure side, within incurved core, there are separation and counter flow in pressure side and core near inlet .when it comes to half section of pump ,the flow switched from pressure side to suction side, so the flow is relatively steady and the velocity of suction side have increased.At the low Low-speed ratio, a large region with low velocity and vortex is found in the front part of the turbine passage and the flow situation is very unstable. Along with speed ratio is rising, the low velocity region is vanished. The field around turbine outlet has a uniform and consistent in most part of flow passage ,except small low velocity region appears in the section of core and suction side. When the speed ratio is high, the velocity is very high and the flow is stable compared to low-speed ratio,but there are counter flow near outlet and shell.The length of turbine is short, and the incidence angle of stator changes in a wide range. When the speed ratio is low, the fluid rushes at the pressure side of stator blade, and a high-pressure region with low velocity is produced at the same position. When speed ratio is high, the fluid don't rush to the pressure side of blade completely, some rushes to the suction side and a wake region with low velocity appears at the pressure side and suction side. In stator, the flow is approximately developed in the span plane. There is no strong secondary flow on spanwise direction. Except for shock loss is high , the hydraulic loss has a uniform distribution from middle to outlet.5.On the basis of flow analysis , choosing starting conditions of torque converter to optimize with Sculptor. Optimization objective is the average pressure of inlet and outlet, creating control groups are constraint variables. After optimization, pressure field have changed a lot.High-pressure and maxium pressure difference have been slowed.At the same time, High-pressure region increases and low-pressure region decreases.As to velocity field,change tendency doesn't change much except some of the high-speed region disappear in pump and turbine.since stator has changed a lot,low-pressure region exist in later_half part and suction side near to inlet,and correspondly,high-speed fuild appears too.6. As the summary of the paper, the sixth part expounded all the work and research results and make prospective to future work.
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