Study On Lubrication And Temperature Performance Of Textured Journal Bearing Considering Cavitation Effect

As an important transmission component in rotating machine,the performances of the journal bearing are closely correlated to the stability and safety of a mechanical system.Under real operating conditions,however,the lubrication faults of the journal bearing may occur due to the insufficient load-carrying capacity,large friction force and excessive temperature rise,which will lead to severe wear and bush-burning of the bearing.Therefore,it is necessary to study lubrication and thermal performances of the journal bearing so as to improve its load-carrying capacity,reduce its wear and temperature rise.With the development of surface micro-machining,it is already proven that the surface texturing shows favorable behaviors in improving the lubrication performances of the journal bearing.But most researches about surface textures neglect the cavitation and thermal effects of the lubricant to date.Besides,the surface textures used in the past researches are mostly simple dimples or microgrooves,so that the improvement of the bearing performances is limited.So it is of great importance to investigate the lubrication and thermal performances of the textured journal bearing with the cavitation and thermal effects.The present study is sponsored by the Chongqing Natural Science Foundation Project(No.cstc2016jcyjA0290)named after "study on the effect of composite surface texture on friction and wear and noise mechanism of sliding bearings",and the National Natural Science Foundation of China(No.51375509)named after “investigation of tribological performances for water-lubricated bearing using representative shell structures of diatoms”.The main research contents are listed as below:Firstly,the mathematical model and lubrication model of the journal bearing with spherical dimples and bumps were established,in which the cavitation effect of the lubricant is considered.By solving the lubrication model of the journal bearing,effects of spherical dimples and bumps on the lubrication performances of the journal bearing were comparatively studied.The numerical results show that the bump can greatly increase the bearing load-carrying capacity but also increase the bearing's friction in comparison with the smooth case.In contrast,dimples can significantly reduce the bearing friction,while it is inferior to the bump in improving the load-carrying capacity.Secondly,the thermal performances of the bearing with the bumps,simple dimples and compound dimples were compared under the consideration of cavitation and thermal effect.The simulation results indicate that compared with the smooth bearing,the overall temperature of the bumped bearing is higher and the overall temperature of the dimpled bearing is lower.In addition,compared to the simple dimple,the compound dimple exhibits a better capability in lowering the temperature of the bearing.After this,the lubrication performances of the journal bearing with compound dimples was studied considering thermal effect.The simulation reveals that compared with the isothermal model,both the load-carrying capacity and friction force of the bearing with the compound dimples decrease.It is also found that under appropriate dimple position,size and interval,the lubrication performances of the bearing with the compound dimples are superior to that of the bearing with simple dimples.Lastly,the friction forces and friction coefficients of different types of textured plates were tested and compared at different external loads and reciprocating frequencies.Meanwhile,the surface morphology of the wear zone for the textured sutaces was observed.The experimental results indicate that among the studied textured plates,the prescribed compound dimples shows the relatively low friction force and friction coefficient in comparison with the simple dimple.This verifies the conclusions obtained by previous numerical simulations to some extent.