Numerical Study On Lubrication Performance Of Crosshead Bearing Of Marine Two-stroke Diesel Engine

The working conditions of crosshead bearing in marine low-speed two-stroke diesel engine are very bad,and the operation safety of diesel engine and even the whole ship power system are affected by its working reliability.In addition,with the continuous development of marine two-stroke diesel engine towards high power density,the working conditions of crosshead bearing become more demanding.Therefore,it is of great practical significance to study and optimize the lubrication performance of crosshead bearings.In this paper,the crosshead bearing of marine two-stroke diesel engine is regarded as the research object,and the influence of surface roughness,elastic deformation and temperature are considered in the thermo-elastic fluid mixed lubrication study of crosshead bearing.The purpose of this paper is to confirm and optimize the lubricating performance of crosshead bearings under the rated condition.Firstly,according to the extended Reynolds equation and the contact theory of micro-convex peak,a thermos-elastic hybrid lubrication model for crosshead bearings is established.Then,the lubrication numerical study of crosshead bearing is carried out by means of multi-body dynamics simulation based on finite element theory to confirm the lubrication performance and working state of crosshead bearing under rated working condition.Finally,the effects of three related factors on the lubrication performance of the bearing are analyzed,such as oil supply characteristics,radius gap and oil bearing structure,and then the optimization scheme is put forward by using orthogonal experimental design method,and the optimization scheme is verified by calculation.The results show that the existence of circumferential oil groove result in the discontinuity of oil film thickness distribution,and cause the double peak phenomenon of oil film pressure and oil film temperature separated by oil groove at the same time.At the edge of the oil groove,the contact pressure is high,the contact time is long,the area is large,so the lower bearing is easy to wear.The minimum filling ratio of lubricating oil leaps from 0.05 to 1 in a short time and there is a large oil film pressure change rate,which leads to cavitation erosion of the lowering bearing easily.The optimum scheme proposed in this paper is as follows:oil supply pressure 1.4 MPa,oil supply temperature 55?,radius gap 0.1mm,oil groove position 90°?140°and 220°-270°(the corresponding oil hole position 115°and 245°),oil groove size 32mm(the corresponding oil hole size 40mm).After optimization,the oil film thickness,oil film pressure and oil film temperature are uniformly distributed,the contact pressure at the edge of the oil groove is eliminated and the minimum filling rate is increased obviously,and the wear and cavitation erosion of the lower bearing are reduced.As the conclusion,the research in this paper not only determines the lubrication performance of the crosshead bearing under rated condition,but also puts forward an optimized scheme and achieves the purpose of improving the lubricating performance of crosshead bearing.It provides a useful reference for the structure design of oil groove of crosshead bearing and the daily management of diesel engine lubrication system.