Study On Lubrication Law And Multi-objective Optimization Of Bearing Of High-pressure Oil Supply Pump

As an important part of mechanical transmission system,bearing has a wide range of functions.In the inte rnal combustion engine industry,high-pressure oil supply pump is often used as one of the important matching systems in the internal combustion engine system because of its strong load capacity and stable operating characteristics.During the high-speed o peration of the camshaft of the high-pressure oil supply pump,the lubricating oil film between the camshaft and the sliding bearing is prone to cavitation,which will cause journal cavitation and affect the stability of the camshaft operation.Therefore,it is necessary to study the lubrication effect of bearing.The lubrication characteristics of the main shaft sliding bearing of the in-line plunger high-pressure oil supply pump are studied.Taking the lubricating oil film of the bearing of the high-pressure oil supply pump as the research object,the geometric model of the oil film is established by using the three-dimensional modeling software cero,and the geometric model is discretized by using the ICEM software.The two-phase flow model and cavitation control model of the lubricating oil film are established by using the fluid analysis software FLUENT,and the grid independence is analyzed.The oil film is divided into four or more grids in the radial dimension,which can ensure the stability of the nu merical calculation results;The effects of spindle speed,oil inlet pressure,lubricating medium viscosity,journal surface roughness,oil film eccentricity and bearing clearance on oil film characteristics are calculated and analyzed.The results show th at when the spindl e speed increases from 1500 rpm to 3500 rpm,the oil film gas volume fraction increases by 42.8% and the oil film bearing capacity increases by 42.3%;When the oil inlet pressure increases from 240 kpa to 360 kpa,the oil film gas volume fraction decreases by 4.2%,and the oil film bearing capacity increases by 24.1%;The kinematic viscosity of lubricating medium increased from 15 c St to 55 c St,the volume fraction of oil film gas increased by 61.6%,and the bearing capacity of oil film increased by 87.2%;The surface roughness is 0.25 μ m-0.4 μ m,the gas volume fraction decreases by 20.04% and the oil film bearing capacity decreases by 6%;When the eccentricity increases from 0.3 to 0.5,the oil film gas volume fraction increases by 29% and the oil film bearing capacity increases by 15.9%;When the bearing clearance increases from 0.04 mm to 0.055 mm,the oil film gas volume fraction decreases by 41.7% and the oil film bearing capacity decreases by26.9%;It is found that the more sensitive factors affecting the oil film lubrication characteristics are spindle speed,oil inlet pressure,lubrication medium viscosity,journal surface roughness and bearing clearance;Taking the spindle speed,oil inlet pressure,kinematic viscosity of lubricati ng medium,journal roughness and bearing clearance as variable factors,and taking the maximum oil film bearing capacity and the minimum oil film gas volume as the objectives,the optimization function model is established.The initial sample points of Kriging proxy model are obtained by using the orthogonal experimental design method,and the proxy model of oil film lubrication characteristics is established,According to the minimum surrogate model prediction criterion（MSP）and the improvement expectatio n criterion（EI）,increase the sample points,repeatedly iterate to ensure the accuracy of the model,and use the NSGA-II algorithm to realize the multi-objective optimization design of lubrication characteristics through the surrogate model.The results s how that after the optimization analysis of Kriging surrogate model,the oil film bearing capacity is increased by 180.8%,but the cavity gas volume is increased by 48.6%.Due to the obvious increase of oil film bearing capacity,the oil film lubrication characteristics are improved compared with those before optimization.