Research On Effect Of Manufacturing Methods On Performance Of Hydrodynamic Torque Converter

The previous studies on performance differences caused by different manufacturing methods of hydrodynamic torque converter are mainly depend on a large number of external tests, which are not easy to be implemented due to their high costs and impossible to compare the difference conditions of their flow field. In order to get a better understanding of the differences between foundry hydrodynamic torque converter and stamping welded hydrodynamic torque converter and their contributing causes, this paper, based on the CFD method and three-dimensional flow theory, made a deep study on the internal flow characteristics of hydrodynamic torque converters with the two different manufacturing methods, compared and analyzed the regular patterns of effect of the two different manufacturing methods on the performance of hydrodynamic torque converter. Thus it enable us to choose different manufacturing methods on torque converter according to different applications and situations so as to improve the performance and efficiency of torque converter.On the basis of a lot of readings about related references, this paper made a contrast analysis on the performance theory of stamping welded hydrodynamic torque converter and foundry hydrodynamic torque converter and got the conclusion that the difference between the two different hydrodynamic torque converters was caused by the thickness distribution of blades in pump and turbine. The blades which in pump and turbine of stamping welded torque converter are of the same thickness; the core, the shell and blades are stamped and welded by steel plate. The blades in pump and turbine of foundry torque converter are streamlined and the core and the shell are also designed by aluminum castings. The stators of the two torque converters are casted, and blades are also streamlined. Based on the data parameters of YJH340 hydrodynamic torque converter, two kinds of hydrodynamic torque converters with different manufacturing methods are designed. These two hydrodynamic torque converters have same number of wheel blades; same inlet, outlet angle and same geometry but with different thickness distribution of pump and turbine blades. Through the use of three-dimensional modeling software, this paper established the physical model of the two torque converters and divided this computational fluid model into mesh. Based on the numerical simulation method of sliding mesh, this paper made the flow field simulation in the stamping welded hydrodynamic torque converter and foundry hydrodynamic torque converter and sorted the results, thus got the original characteristics of the two torque converters.According to the transient numerical results simulated by three-dimensional flow field, the internal distribution characteristics of stamping welded hydrodynamic torque converter and foundry hydrodynamic torque converter were achieved. Through the comparison between the flow fields of these two hydrodynamic torque converters, the result that the overall distribution of pressure and velocity in stamping welded hydrodynamic torque converter was not as uniform as that of foundry hydrodynamic torque converter was achieved. Under the low speed ratio, the high pressure area which distributed in the foundry's pump and turbine were smaller than that of stamping welded hydrodynamic torque converter, but the distribution was uniform. The high speed distribution area was bigger than that of stamping welded hydrodynamic torque converter, and the change of stator was not significant, but the velocity of foundry hydrodynamic torque converter decreased. Under the high speed ratio, the overall pressure and velocity in foundry hydrodynamic torque converter was lower than stamping welded hydrodynamic torque converter, but the distribution was more uniform, and the low pressure area of pump and stator was reduced, the pressure difference of turbine was also decreased, which lead the secondary flow of deterioration decrease accordingly. Due to the same thickness of blades of stamping welded hydrodynamic torque converter, the flow in pump and turbine was not totally realized and there existed a certain range of low-speed flow area, flow separation and higher velocity gradient in the central region of the flow channel where the curvature change of blades remain largest. The irregular distribution of the speed which can consume the main areas'energy transfer was also one of the major factors which affected the converter efficiency. However, because of the blades in foundry hydrodynamic torque converter were streamlined, the working medium in the flow channel was more fluent and the flow channel of each wheels can totally work, especially in the biggest area which curvature change occur largest, the phenomena of current deterioration reduced, the efficiency was promoted, thus good performance was relatively achieved.According to the numerical solution of pressure and velocity, the performance of stamping welded hydrodynamic torque converter and foundry hydrodynamic torque converter was calculated. Through the contrastive analysis of the performance, the macro external characteristics of these two hydrodynamic torque converters were achieved. Through the four aspects of flow rate, torque coefficient, torque ratio and efficiency, the performance of these two torque converters with different methods was compared. The flow rate of working medium in stamping welded hydrodynamic torque converter was bigger than that of foundry hydrodynamic torque converter, besides, under the whole condition, the torque coefficient of pump was also higher than that of foundry hydrodynamic torque converter, which got its maximum difference in the medium speed ratio condition, this indicates that when the external characteristics of engines keep the same, the torque capacity of stamping welded hydrodynamic torque converter was larger, the size of torque converter's which match the engine can be smaller. However, stall torque ratio of foundry hydrodynamic torque converter was 5% lower than that of stamping welded hydrodynamic torque converter, but with the increase of speed ratio, the foundry began to close to the stamping welded, and when at i=0.75, the foundry hydrodynamic torque converter was a little higher than the stamping welded one. Through the comparison of efficiency, it can be concluded that the stamping welded was better than foundry one when under the low speed ratio condition, but with the increase of speed ratio, the foundry hydrodynamic torque converter with streamlined blades was better and be more efficient in the area of high speed ratio conditions.