Research On Numerical Simulation And Casting Technology Of Hydrodynamic Torque Converter Impeller

Casting is the main and common method in production of hydrodynamic torqueconverter impeller. The structure continuity of foundry hydrodynamic torqueconverter is good, and its impeller is made up of different thickness streamlinedblades, that can reduce the phenomenon of flow deterioration of working medium.Foundry hydrodynamic torque converter has advantages like large braking modetorque coefficient, wide high efficiency range, higher efficiency etc. At present,studies on hydrodynamic torque converter were mainly focused on the structureimproving, the flow field analysis, power matching etc, but very few reports weredevoted to the study on casting process of hydrodynamic torque converter, andmethods were also old. With the application field of hydrodynamic torque converterexpanding, requirements on casting quality, precision, reliability, economy andenvironmental protection become higher and higher. Therefore, it is necessary toadopt advanced numerical analysis method to make systematic and in-depth researchon casting process of hydrodynamic torque converter, so as to optimize the foundrytechnology and improve the casting quality. In this thesis, systematic studies onhydrodynamic torque converter were carried out in terms of casting processsimulation, casting defect prediction, the influence of process parameters on castingprocess and different casting methods comparison. The research work and conclusionsare listed as follows:1、Casting system design of hydrodynamic torque converter impeller andestablishment of the grid modelCasting systems of hydrodynamic torque converter which circulatory circlediameter was335mm were respectively designed according to technologicalcharacteristics of gravity casting, low pressure casting as well as centrifugal casting.Meanwhile, the sheetbody structures of assembled casting system were divided into finite element grids. With this method the match degree between casting and mouldgrid models could be enhanced, and grid errors such as overlapping surface, bad unitwere reduced. The efficiency and accuracy of meshing were improved, and theconvergence of numerical calculation and the accuracy of analysis results could beguaranteed.2、Filling and solidification process simulation and casting defect predictionThe filling and solidification processes of gravity casting and low pressurecasting as well as centrifugal casting of hydrodynamic torque converter were real-timeobserved with the application of casting process simulation software. Flowcharacteristic and regularity of the liquid metal in the mould cavity were in-depthresearched. During solidification process, the influence of temperature gradientchange on casting quality was analyzed. An accurate and scientific prediction ofcasting defect had been gotten. The research result shows that the flow stability ofliquid metal during filling process and solidification sequence of casting duringcooling process would produce crucial impact on casting defects like shrinkage cavityand porosity.3、The influence of different process parameters on casting process and castingqualityDifferent casting methods have their own main process parameters. Contraposinggravity casting, low pressure casting and centrifugal casting process of hydrodynamictorque converter impeller, the influence of pouring temperature and pouring speed,filling pressure, rotational velocities on casting process and formation quality hadbeen researched respectively. The research result shows that without changing theoriginal structure of impeller or external cooling condition, parameter adjustment thatcan improve filling capacity of melting metal would cause a certain degree expansionof shrinkage cavity and shrinkage porosity. On the premise of ensuring casting formed,pouring temperature, pouring speed, filling pressure and rotational velocities shouldbe chosen as low as possible in the process of actual production.4、 Characteristics and application scope of different casting methods ofhydrodynamic torque converter impeller Casting technological characteristics about these three casting methods ofhydrodynamic torque converter impeller were contrastively analyzed. Gravity castingis simple and convenient. It is a flexible and low-cost production method but withpoor product quality and low production efficiency. The mechanization level of lowpressure casting is higher, and casting quality is much better, but the additional cost isslightly higher. The forming process of centrifugal casting is very rapid. Theintroduction of centrifugal force field is beneficial to filling and feeding of moltenmetal. But the centrifugal casting process of hydrodynamic torque converter impelleris still in the exploratory stage and not very mature at present. In the actual production,appropriate casting method should be selected according to the batch of products,application field, the quality requirements and other factors in order to achievemaximal value of production.