Simulation And Experimental Study On The Drag Torque Losses Of Large-size Multi-plate Wet Clutch

Wet clutch has many advantages,such as large capacity of transmission torque,smooth engagement and uniform wear.Especially for the wet clutch which has large-size friction plates,is widely used in crawler vehicles because of its greater torque transmission capacity,smaller heat generation per unit area and longer service life.In this paper,the outer diameter of the large-size friction plate in the wet clutch selected for research is 428.5mm,far greater than other vehicles'outer diameter,that is not exceeding 150mm generally,which is of great research significance.At the same time,the research shows that,when the wet clutch is idling,the oil between the frictio n pair produces the belt-row torque due to the shearing stress.On the one hand,it will generate heat and cause the buckling deformation of the friction plate;On the other hand,it will cause drag losses.Therefore,reducing the torque generated during idling is crucial to improve the performance of a wet clutch.The main contents are as follows:(1)Study the relevant equations of hydrodynamics,the boundary conditions of flow field model and the calculation method of convective heat transfer coefficient.In Solidworks,create three-dimensional models of wet friction plates with four different typical oil groove structures,complete necessary simplification.Import the models into fluent software,and then generate mesh and set the boundary conditions.Carry out the dynamic simulation.Meanwhile,dynamic simulation also be carried out on the actual oil flow field.(2)On the basis of the traditional mathematical model of drag torque,consider the influence of lubricant flow rate and centrifugal force on the drag torque,and the relationship between the radial velocity of lubricant and the relative rotation speed of friction pair,obtain the oil film equivalent radius,and establish another new drag losses model.Present three mathematical model with different typical oil groove structures.(3)Aiming at the phenomenon of oil film shrinkage,study the air-oil two-phase flow characteristics inside the wet clutch.Take one of the friction plates as an exanple,simulate and analyze the drag losses in the process of idling.On the basis of this,study the effects of the lubricating oil flow rate,lubricant viscosity,clearance of friction pair and friction plate groove structure on the drag torque.The sensitivity of the above parameters to the drag torque is calculated,and the greatest influential one is found out.(4)Setup a "high-speed friction element drag torque testing system",write control and data acquisition program based on the LABVIEW language,and then conduct the test analysis of the process of idling.The test results are compared with the simulation results to verify the correctness and validity of the simulation model.