Theoretical And Experimental Study On Lubrication State And Thermoelastohydrodynamic Characteristics Of Large Eccentricity Journal Bearing

Journal bearing is widely used in rotating machinery as an important supporting part.Especially in heavy equipment,journal bearing often works in the large eccentricity condition,and the oil film thickness would decrease.When the film thickness is similar to surface roughness size,it is easy to appear asperity contact,so that the bearing works in mixed lubrication state.At the same time,the elastic deformation of bush and lubricant thermal effect will also affect the lubrication state and friction characteristics of journal bearings.Therefore,it is necessary to study the mixed thermoelastohydrodynamic characteristics of journal bearing under the large eccentricity condition,so as to provide a useful reference for the design of heavy-duty slide bearing.In this paper,journal bearing under large eccentricity condition is taken as the research object to carry out systematic theoretical analysis and experimental research on its lubrication characteristics.The main research contents are as follows: Based on fluid lubrication theory,a mixed lubrication model for thermoelastohydrodynamic characteristics was established,which was coupled with the average flow generalized Reynolds equation,oil film energy equation and heat conduction equation of bush.This model takes into account the thermal effect,bearing elastic deformation,asperity contact and viscosity temperature-viscosity relationship.On this basis,a mathematical model was established to analyze the influence of journal misalignment on bearing characteristics.The finite difference method was used to discretize the mathematical model.And the distribution of film pressure,contact pressure and temperature field under different working conditions was obtained by writing C program.Then,the influences of thermal effect,elastic deformation and journal misalignment on lubrication state transition and bearing characteristics were analyzed.Lastly,a temperature measuring device was built to measure the temperature and load characteristics under different lubrication states based on the improved HS-A hydrodynamic journal bearing test bench,and the rationality of the theoretical model was verified.Theoretical and experimental results show that:(1)The thermal effect and journal misalignment make the bearing more prone to mixed lubrication state,and the elastic deformation reduces the asperity contact load.(2)The asperity contact increases the frictional heat,and the temperature peak is formed at the minimum oil film position under large eccentricity condition.Thermal effect and bearing elastic deformation make the contact pressure concentrated at both ends of the bearing,and load capacity and frictional force both have decreased.(3)Journal misalignment makes the pressure field,temperature field,oil film thickness and elastic deformation of bearing asymmetrically distributed along the axial direction,and has obvious end sides effect.In a certain range,the frictional force and side leakage flow increase obviously with the increase of misalignment angle.(4)In the experimental study,the bearing works in mixed lubrication state under heavy load condition,and the pressure and temperature value of lubricant increase with the increasing of speed and load.Besides,the higher temperature value appears at the position of the minimum oil film thickness.The theoretical calculation has a good agreement with the experimental results.