Lubrication Analysis And Optimization Of Main Bearing Of Diesel Engine Based On Multi-body Dynamics

Crankshaft main bearing is one of the most critical friction pairs in internal combustion engine.Its lubrication performance is directly related to the reliability and durability of internal combustion engine.The technical requirements of high reliability,high power and low fuel consumption of high-power marine diesel engine make the enhancement indexes of maximum combustion pressure and average effective pressure continuously improve,and put forward higher requirements for lubrication performance of main bearing.The coupling analysis of dynamics and tribology of bearing system by multi-body dynamics method can accurately predict the lubrication performance of bearing and reduce the risk of product development.In this paper,the main bearing of a marine diesel engine crankshaft is taken as the research object.The AVL-EXCITE software is used to establish the main bearing elastohydrodynamic lubrication analysis model considering the factors such as the filling rate of the lubricating oil,the elastic deformation of the bearing surface and the surface morphology of the bearing.In order to verify the correctness of the modeling method,a sliding bearing test rig was established,and oil film pressure and friction measurement tests were designed under different rotational speeds and oil supply pressures.The relationship between oil film pressure and oil supply pressure,friction and rotational speed was obtained.The AVL software is used to simulate and analyze the experimental platform.The validity of the modeling method is proved by comparing the experimental results with the simulation results.Applying the main bearing elastohydrodynamic lubrication analysis model established in this paper,the main bearing is lubricated and analyzed,and the oil film thickness,oil film pressure,axial trajectory,friction loss and oil film pressure distribution under dynamic load are obtained.Through the analysis of the calculation results,it is found that a large asperity contact pressure occurs at the edge of the main bearing tile,that is,the bearing bush is eccentrically worn.In order to reduce the eccentric wear of bearing bush,this paper designed a ten-factor three-level orthogonal test to study the influence of oil supply pressure,oil groove width,lubricant type,surface roughness,alloy layer thickness of bearing bush,radius clearance and double conical bush on the lubrication performance of bearing.The results show that the radial thinning amount of the bearing bush has a significant influence on the minimum oil film thickness,the maximum oil film pressure and the maximum asperity contact pressure.The influence of the lubricating oil type,the oil supply temperature and the radius gap on the friction loss is highly significant.On this basis,a bearing modification design scheme aiming at reducing friction and loss is proposed,which provides theoretical guidance for bearing optimization design.