Numerical Simulation Analysis Of Torque Converter's Internal Flow Field

The thesis is based on an existed mature hydraulic torque converter ,using similarity principle and the other principles ,and also with the help of commercial software such as CATIA and FLUENT to calculate and analyze the flow field of the torque converter.At last summarizes the portraits and the influence factors of the flow field .The main content of the thesis is as below:(1) First introduces the practical significance of the research contents ,Then ,the hydraulic torque converter is necessarily introduced, such as its structure, classification, working principle and its advantages and disadvantages, and also introduces the theory basis on the process of research, Finally, introduces the present research of the hydraulic torque converter's internal flow field , mainly introducing some advanced measuring technology ,the important software FLUENT and the contents and methods of the torque converter experiment.(2) Introduces the basic knowledge of hydraulic transmission. First, it is the four similar laws established according to the similarity principle .Then, introduces the three main fluid motion equation including: flow equation, Bernoulli equation and Euler equation with the general form .Then, introduces the basic knowledge of the three-dimensional flow field of the torque converter, mainly including the sticky fluid's motion differential equation, Reynolds equation and the calculation method of turbulence, The last is the three-dimensional flow field numerical analysis method, the finite volume method is mainly introduced, which is used in this paper as the numerical analysis method.(3) The model building and some conditions setting before the numerical analysis. First, use the similarity principle, with the help of CATIA, to build a new model. Then, with the help of GAMBIT, build the model grid. In order to facilitate the numerical simulation analysis, there are some hypothesis, Then, give some concrete condition settings to the meshed model in the software FLUENT, which is crucial to the accuracy of the results, for example: the import surface is set as speed import boundary condition, export surface as pressure export boundary condition, the turbulence model is set asκ-εmodel, coupling model for speed is set as SIMPLE ,which is suitable for the thesis research, the discrete form is set as first-order windward format, which is correct. And also there is correct setting for the convergence. Finally summarize the process of calculation and analysis in the form of diagram.(4) It is about numerical simulation and analysis of the three-dimensional fluid field, which is the core of the paper. To pump wheels, turbine and stator, there are detailed analyses about the pressure and velocity field in three conditions (i=0.00, i=0.4, i=0.8). Through the analyses, we have a deep understanding of the distribution of the internal flow field.The conclusion is as follows:(a) Pump wheelPressure field: Generally speaking, the pressure from import to export is gradually reducing. At any condition, the distribution of pressure in the same plane is uneven, which is also the same between the different planes. The pressure distribution under the middle speed ratio and efficient condition is similar, but these two conditions have big difference from the starting conditions, mainly because in the starting condition the pump rotates alone without having the influence from the turbine.Velocity field: The distribution of velocity vector between the two conditions (i= 0.4, i=0.8) is almost the same. But these two conditions are different from the i=0.00 condition, the reason is the same as the above. There are reasons like the existence of blades camber and machining precision, so, inside the pump, the places like secondary flow, vortex and reverse current exist. These areas will greatly affect the pump efficiency, so we should pay more attention to it, trying to reduce their existence ranges.(b) TurbinePressure field: The pressure fields between the two conditions (i=0.00, i=0.4) is almost the same, because under these two conditions the pump flow field has little changes, and when the speed ratio is 0.40, the speed of turbine is very low. But the pressure distribution is very even on the whole when the speed ratio is 0.8, because the fluid flows into the turbine without impact which greatly improves the flow condition.Velocity field: In the first half of the passage, the flow speed is very high at the non-working plane. While in the second half, with the rotating speed increasing, the distribution of velocity vector is more and more even. There is no obvious difference between the two conditions (i=0.00, i=0.4).But at the highest efficient condition, the internal flow field distribution of velocity vector is very even, the reason is as same as the pressure field's. The curvature change of inner surface is the biggest one in the turbine, so at this place the phenomena, such as secondary flow, reverse current and so on, are serious. In the outer surface there are also such areas, the appearance of these areas have greatly reduced the hydraulic efficiency of turbine, therefore, we should further optimize turbine leaf in order to reduce the loss of energy.(c) StatorPressure field: From the working surface to non-working surface, the pressure is reducing gradually. Because the pressure's and the velocity's distribution on the turbine export surface changes very little, and also the stator is always in stillness, under these three conditions, the pressure distribution in the internal flow field changes very little. Velocity field: The sector of the non-working surface near the import surface is the low speed area, while the sector of the export surface near working surface is the high speed area. The sector of inner surface near the working surface is also high velocity vector area; the velocity vector distributions of internal flow field, under the three conditions, are almost the same, the reason is as the same as the pressure field's.(5) The summary of the whole thesis, including the content of papers, research conclusions and existed deficiencies in the thesis.