Research On Elastohydrodynamic Lubrication Characteristics Of High Power Diesel Engine Main Bearings

The main bearing is one of the important friction pairs in diesel engine.With the rapid development of diesel engine,high speed,high power,high density and low energy consumption become its important development direction,which puts forward higher requirements for the key motion pair main bearings of diesel engine.The lubrication performance and working condition of the main bearings directly affect the durability and efficiency of the whole machine.High explosion and high speed make the main bearing need to bear more alternating load and the working condition is more demanding.Therefore,considering a variety of practical factors,analyzing the lubrication performance of the main bearing of diesel engine under power lifting is of great significance to the optimization design of diesel engine.In this paper,V12 high-power diesel engine is taken as the research object.Based on elastohydrodynamic lubrication theory,finite element theory and nonlinear multibody dynamics theory,The elastohydrodynamic lubrication simulation model(EHD2)of the main bearings of the diesel engine was set up in EXCITE Power Unite.The lubrication performance of the main bearings of the diesel engine at the calibrated speed is analyzed,including the minimum oil film thickness,peak oil film pressure,asperity friction power loss,hydrodynamic friction power loss and total friction power loss.The sixth main bearing was selected to analyze the influencing factors of lubrication performance.According to the analysis results,the corresponding improvement scheme was put forward to provide guidance for the design of high-power diesel engine.The research results show that:1?The minimum film thickness of each main bearing is greater than the minimum allowable value of 1 ?m,meeting the requirements.But the minimum oil film thickness of the sixth and seventh main bearings is lower than others;The peak oil film pressure of the first to the sixth main bearing is all less than the maximum allowable value of 150 MPa,meeting the requirements.However,due to the influence of flywheel on the seventh main bearing,the tilt of shaft neck is relatively serious and the peak oil film pressure is relatively high,exceeding the maximum allowable value of 150 MPa.Combined with the 2D cloud map of the main bearings,it is found that each spindle neck has different degrees of inclination,and on thelower bearing bush and two ends of the bearing the oil film pressure is higher and the oil film thickness is lower.2?Bearing clearance,lubricating oil viscosity,groove parameters,bearing surface morphology,bearing shape error,bearing width,journal diameter and crankshaft balance have a great impact on the lubrication performance of the main bearings.The influence of oil supply pressure and oil hole parameters on the lubrication performance of the main bearings is relatively small.The analysis results can provide a reference for improving the lubrication performance of the main bearing.3?The structural parameters of V12 high-power diesel engine are improved,including the parameters of main bearing and crankshaft.The minimum oil film thickness of all main bearings is increased after improvement,and the peak oil film pressure of all main bearings was less than 150 MPa,especially the seventh main bearing showed a significant decrease in peak oil film pressure.Total friction power loss is reduced for all main bearings.