Research On The Flow-state Of The Flow Field In The High-speed Cylinder Of Wet Clutch Of Heavy-duty Off-road Vehicles

In recent years,the heavy-duty off-road vehicles gradually develop to the direction of high-power,and the performance demand of the transmission system under high-power conditions is constantly increasing.As a key part of the transmission system,the wet clutch has the characteristics of large transmission torque and long service life,and is used in heavy-duty off-road vehicles widely.In the process of connection and separation,the coordinated drive of a high-speed cylinder system is needed.Therefore,the research on the flow field characteristics of high-speed cylinder of the wet clutch was conducted to improve the performance of the wet clutch and transmission system.The paper mainly researched the shifting and oil-filling characteristics and the steady-state characteristics of the high-speed cylinder in the wet clutch using the method of computational fluid dynamics simulation.The results provide a substantial theoretical basis for precise control of the oil-filling process and the structure design of the high-speed cylinder.The specific research work of the paper is as follows:?1?The theoretical model of high-speed cylinder system in the wet clutch was established,and the theoretical research on the inlet passage,the main cylinder,the return cylinder and the piston in the high-speed cylinder system was conducted to obtain the piston-driving equation of the high-speed cylinder system and optimize the simulation model according to the theory.?2?The fluid domain model of the high-speed cylinder in the wet clutch was established,and was divided into three parts:the static region,the inlet passage and the main cylinder,and then meshed with hexahedral grids.Based on the grid model,completed the transient simulation of the flow field in the high-speed cylinder in the process of shifting and oil-filling using the dynamic mesh technology.And then analyzed simulation results from four aspects:the change of oil volume fraction,the change of outlet flow rate,the change of pressure and the law of piston motion to further explore the oil-flow state of the high-speed cylinder in the process of shifting and oil-filling the clutch.?3?Based on the fluid domain model of standard size high-speed cylinder,12 fluid domain models with different structure sizes?inner diameter R₂,outer diameter R₄ and axial width b?were established to complete the steady-state simulation.Based on the steady-state simulation results,the influence mechanism of inlet pressure,cylinder speed and structure sizes on the fluid pressure field and velocity field were studied.In addition,the centrifugal oil pressure in the internal flow field was studied,and the concept of the lag coefficient was proposed.The relationship between the lag coefficient and inlet pressure,cylinder speed,structure sizes was studied through simulation.Inlet pressure has no effect on lag coefficient.Lag coefficient is positively correlated with outer diameter.Lag coefficient is negatively related to inner diameter,axial width and cylinder speed.Based on the simulation data,the quantitative relationship between the lag coefficient and cylinder speed,cylinder structure size is further determined,and the calculation method of correcting centrifugal oil pressure was put forward.?4?The test verification is carried out on the comprehensive performance test device of the high-speed cylinder was set up,and the high-speed cylinder test piece was designed.The fluid domain of the test piece was extracted and the fluid simulation was carried out to obtain the simulation data of the pressure and flow.Designed the test scheme of the pressure and flow characteristics,completed the comprehensive performance test of high-speed cylinder according to the scheme.The rationality and correctness of the research method in the paper were fully verified by the comparative analysis of test data and simulation data.