Simulation And Analysis Of Bearing Lubrication State And Dynamic Strength Of Diesel Engine

The crankshaft is one of the most important compoments of diesel engine, which endures complex loads, it directly affect the performance reliability, economical and the whole life of the engine. It has important significance when making research of the crankshaft bearing lubrication and dynamics strength. Through the muti-body system dynamic analysis, we can predict the vibration, lubrication and strength of crankshaft system, to lay the foundation of optimal design of crankshaft system.The traditional analyze methods are so simply that they can not be satisfied with the actual demands. A method that combined finite element method with multi-body dynamies simulation is applied to carry on dynamics analysis simulation on the 6L16/24 diesel engine crankshaft system in this article. First, establishes reasonable diesel engine crankshaft system dynamic model, complete the simulation in an action cycle. According to the result of torsional displacement and speed motion and so on, proves the crankshaft system models are reasonable. Second, carry on the lubrication calculation of crankshaft bearing of diesel engine, work out its bearing force, film pressure, film thickness, friction loss power and orbital path in an working cycle, the lubrication condition of main bearings is analyzed. It considers the elastic deformation of the bearing wall, shell, and the surface roughness of the journal and the shell while dynamic simulation. Makes a coupling analysis of oil film thickness, oilfilmpressure, elastic deformance, surface roughness when using the finite difference method and the finite element method. Mean while, when considering the bearing clearance, oil temperature, oil supply pressure parameter on the engine crankshaft bearings, the paper makes a detailed EHD study. The results show that these parameters are significant effect to the bearing lubricatlon properties. It can be contributed to the optimizational design of bearings if these factors are considered adequately.Finally, extract the dynamic load that is obtained by the dynamic simulation, proceed the data recovery by NASTRAN, then carries on the transient analysis of the crankshaft. The data recovery method avoid dealing with complicated dynamic boundary condition by traditional method. The results indicate that, the maximums stress of the ankshaft is within its allowable seope, the rigidity of crankshaft is enough and the distortion is slight. The maximum stress of different time interval is all oceurred on the knuckles of main journal and rod journal. There for the knuckles are important points in the struetural design and optimimization. Combined the finite element method with nonlinear multi-body dynamics simulation software EXCITE to research the dynamic strength of crankshaft system, considering the coupling effect of bending and torsion, the crankshaft's dynamic stress was computed in the whole operating cycle. Based on the dynamic stress, the fatigue strength was computed. Comparison with the traditional finite element method, the crankshaft's flexible affect cound not be neglected when the crankshaft calculation of bearing lubrication and strength was conducted. The fatigue strength analysis method based on the dynamic stress was more convincing than the conventional strength analysis method.