Research On Mathematical Model, New Design Methods And Internal Flow Field Of Hydrodynamic Torque Converter

Hydrodynamic torque converters are widely used in car, bus, construction machinery, military vehicle etc. and greatly improve these vehicle's traction performances. However, an obvious disadvantage of a hydrodynamic torque converter is that its efficiency is not high enough. Because of the extreme complexity of hydrodynamic torque converter flow field, myriad problems have not been solved yet. Therefore, it is necessary to profoundly investigate the design theory and design method.In this thesis, the mathematical model, design method, modeling technique and internal flow field of three-element centripetal turbine hydrodynamic torque converter are investigated. After widely collecting and profoundly studying large amount of domestic and overseas literatures, various approaches are used for the investigation, such as establishing mathematical models, deriving equations, developing program codes, drawing curved lines and three-dimensional solid objects, numerically simulating flow filed, testing etc.In order to describe the flow field of a hydrodynamic torque converter, a new three-dimensional coordinate system, generalized torus coordinate system, is proposed. The complicated particle movement is decomposed into a meridional component and a torus component. A universal meridional streamline equation is derived. According to the relation between the converter wheel velocity polygon and its blade angle, a torus streamline differential equation is established. By integral calculus, torus streamline equation of each wheel is obtained.Subsequently, the influence of streamline bending inertia force on power loss is investigated. The theoretic derivation result shows that as long as the velocity magnitude and the path scroll angle are given, the accumulation effect is a constant and independent of the intermediate path. An important conclusion drawn is that the maximum inertia force rather than its accumulation effect plays a predominant role in the power loss. As a result, the reasonability of the circular torus is verified. In addition, Ejiri E and Kubo's testing result, overall performance deteriorates if the flatness ratio is reduced to less than 0.2, is explained reasonably.The design methods of hydrodynamic torque converter are investigated as well. Three kinds of new design methods are put forward: torus streamline design method, double circular arc design method and plane streamline design method. On the other hand, an analytic streamlined blade thickness function is given. Finally, blade camber line equation, blade surface equation and three-dimensional streamline equation are obtained.In order to simlate the filed of hydrodynamic torque converter, automatically modeling technique is put forward. After the flow passage geometry of hydrodynamic torque converter is fully considered, 5-face revolving element, 8-face revolving convex element and 6-face revolving element are used to construct passage models. Their performance characteristics are found.In the course of flow field simulation, 8-facet convex elements are used to construct pump and stator passage models, while turbine passage model is constructed by solid object slicing. The models are successfully loaded in Gambit. Therefore, the flow filed simulation is performed.A turbine, designed by using plane streamline design method, was tested, so as to verify the philosophy of plane streamline design method. The test result is analysized.In summary, because of the research result of this thesis, the difficult flow description problem of hydrodynamic torque converter is solved and a new analytical research and design system has been established. On one hand, the result deepens the research theory of hydrodynamic torque converter. On the other hand, the result renews the design method of hydrodynamic torque converter and the traditional conformal mapping method, which has been applied for decades, can be abandoned. Therefore, the research result is of engineering application value. In addition, the various formulas established in this thesis make program code design more convenient and lay a solid fundation for the design software development of hydrodynamic torque converter.