Study On The Lubrication Performance Of Surface Textured Journal Bearings

Journal bearing is an important supporting part in a mechanical system,and its performance has an essential influence on the efficiency and service life of the whole unit.Therefore,the study of hydrodynamic lubrication simulation about the bearing is important theoretically and practically.In recent years,as an effective means to improve lubricant conditions and reduce friction,surface texture has been attracting researchers'attention.Introducing surface texture into journal bearings and researching the tribological performance of textured bearings provide a new method for bearing design,as well as improve bearings' working performance.In this thesis,a steady-state journal bearing lubrication model which takes thermal effects into consideration was developed.The model was discretized by finite difference method.In addition,Newton-Raphson method and the sequential scan method were used to get pressure and interfacial temperature respectively.Results showed that the pressure and interfacial temperature distribute symmetrically about the middle section in width,and the maximum amplitude obtains in the middle section;the pressure at the bearing boundary and end faces is equal to ambient pressure,while interfacial temperature is higher than ambient temperature.Then,based on the model of steady-state bearing lubrication,a transient bearing lubrication model was developed with a dynamic analysis of connecting rod small end under piston's reciprocal working conditions.Bearing eccentricity,minimum oil film thickness and maximum oil film pressure were given.Results showed that with the increase of engine speed,reciprocating inertial force will replace gas force and become main source of bearing load;engine speed is an important factor influencing lubrication performance of the connecting rod's small end and an optimal value will produce the best lubrication performance.Based on the steady-state journal bearing lubrication model,and taking the bearing eccentricity,friction coefficient,non-dimensional maximum temperature and leakage flow-rate as evaluation indicators,the effects of two types of surface textures,including dimple-type and groove-type on the lubrication performance of the journal bearing were studied.It was found that textures' location,depth,width(density),shape and relative direction have great impacts on the bearing lubrication performance and optimal textured parameters can improve lubrication performance;under different operating conditions,the bearing has different optimal textured parameters and the texture exerts different effects on improving the lubrication performance.In conclusion,the lubricating properties of journal bearings under steady-state and transient conditions were analyzed.In addition,the impact of surface texture on journal bearing lubrication under steady-state was completed,which provided a theoretical basis for textured bearings' experimental research and application.