Characteristic Analysis Of Four-Stroke Diesel Engine Crankshaft Lubrication Based On Multi-body Dynamics

Internal combustion engine is a kind of heat engine that can change the chemical energy of fuel into mechanical energy.As an important internal combustion engine,diesel engine is widely used in ships,automobiles and other equipment.Crankshaft is an important part of the diesel engine.The action of crankshaft is to turn the reciprocating motion of the piston into the rotation motion,then to collect and output the power of each cylinder and so on.In this thesis,the lubrication characteristics of a four-cylinder diesel engine crankshaft-bearing model were analyzed by the finite element theory and the multi-body dynamics theory combined with the simulation means.Firstly,the three-dimensional model of crankshaft-bearing was established according to the structural characteristics of crankshaft-bearing of diesel engine,and then the mesh dividing and dynamic reduction were carried out.Then,the multi-body dynamics model of crankshaft bearing was established.A working cycle of diesel engine is taken as the research object;the lubricating characteristics of the diesel engine under rated speed and normal working condition were analyzed.The important parameters such as maximum oil film pressure,minimum oil film thickness,average total friction power consumption,peak contact pressure and axial trace were obtained,and the accuracy of the crankshaft-bearing model was verified.At the same time,the influence of the parameters such as crankshaft bearing clearance,oil supply pressure and temperature and lubricating oil groove width on the crankshaft lubrication characteristics is analyzed by combining the average flow model and Greenwood/Tripp theory.The characteristics of the crankshaft-bearing lubrication under different parameters are obtained.The appropriate parameters are selected to optimize the fourth main bearing of the diesel engine.On the basis of the above research,the dynamic coupling between the thermo-elastic fluid and the lubricating oil film was considered.The simulation model of the crankshaft multi-body dynamics is established,and the lubrication characteristics and influencing factors of the main bearing of the diesel engine were analyzed.This provides some technical support for the optimization design and model improvement of diesel crankshaft-bearing.