Study On Influence Of Lubrication And Friction Properties Of Textured Key Friction Pairs In Methanol Engine

As a new clean alternative fuel,methanol has significant advantages in power performance and emission performance.However,methanol has the characteristics of low viscosity and high latent heat of vaporization,and unburned methanol flows into the oil pan and dilutes the lubricating oil,which will adversely affect the lubricity and durability of the key components of the internal combustion engine.In this paper,the plunger couple and the cylinder-liner piston ring of the key friction pairs in methanol engine are studied.The effects of surface texture on the lubrication performance of the key friction pairs are studied through the numerical simulation and friction test.First of all,the tests are completed according to the lubricating oil solubility test standard and the corrosion performance test standard of petroleum products,and the influence of dilution rate on the physical properties,chemical properties and corrosion resistance are analyzed.The friction and wear mechanism of the lubricating oil diluted with methanol is investigated by the friction and wear test.The results show that the limit dilution value is 15%,exceeding the limit dilution value will bring bad influence to the lubrication performance,wear resistance and corrosion resistance of methanol engine lubricating oil.When methanol is added to the lubricating oil,the color of the diluted mixed solution become darker,the viscosity decreases,the total acid number increases and the total base number decreases.Through the corrosion analysis test of methanol diluted lubricating oil and the friction and wear test of ball block friction pair,it is found that when the dilution rate exceeds 15%,the corrosion effect of the diluted mixed solution becomes more obvious,and the corrosion degree of the copper surface begins to intensify.With the increase of the dilution rate,the friction coefficient of each scheme gradually increases and the wear scar width keeps increasing.The results show that methanol dilution of lubricating oil phenomenon would reduce the corrosion resistance and wear resistance of engine lubricating oil.Secondly,through the establishment of textured plunger couple lubrication model,the lubrication performance of the textured plunger pair is calculated,calculating the optimal surface texture parameter and analyzing the influence of texture parameters on lubrication performance optimization of the plunger couple.According to the plunger couple friction and wear test,exploring the influence of surface texture on lubrication friction and wear performance of methanol engine plunger couple.The simulation results show that the pit depth has the best effect on the lubrication performance of the plunger pair,and the influence of the pit area occupancy ratio is the least.With the increase of the pit area occupancy ratio,the lubrication performance of the plunger surface is gradually improved.The optimal surface texture parameter is as follows:diameter 50μm,depth 5μm,area occupancy ratio 0.2.The texture size can achieve the best surface lubrication performance of the plunger pair in methanol lubrication condition.The hydrodynamic pressure effect of the pit texture is the strongest and the asperity friction force is less than the nontextured scheme.The experimental results show that the average friction coefficient in methanol lubrication is higher than that in diesel lubrication for the non-textured scheme.Under the methanol lubrication,the average friction coefficient reduction of the textured scheme is 3.4-6.2%compared with the non-textured scheme and the friction coefficient of the textured scheme in methanol lubrication condition reaches the level of the non-textured scheme in diesel lubrication.Under the methanol lubrication,the radial depth of the textured plunger pair is 9.13μm.Compared with the non-textured plunger pair,the wear depth of the textured plunger pair is reduced by 16.2%,and the wear reduction degree of the textured plunger pair in methanol lubrication is greater than that in diesel lubrication.It is shown that the surface texture can be applied to methanol lubrication conditions and improve the lubrication performance of the plunger surface.Meanwhile,the surface texture achieves the objective of reducing wear on the plunger surface.Finally,through the establishment of textured cylinder liner-piston ring lubrication model,the influence of different pit parameters on the lubrication performance of the cylinder liner-piston ring friction pair are calculated and analyzed.Combined with the lubrication friction test,the influence of surface texture on the lubrication friction performance of methanol engine cylinder liner-piston ring is investigated.The simulation results show that the optimal surface texture parameter is as follows: diameter 80μm,depth 5μm,area occupancy ratio 0.1,the 15% dilution scheme has the most obvious improvement effect on the lubrication performance of the cylinder liner-piston ring.The experimental results show that for the non-textured scheme,the average friction coefficient of 30% dilution scheme increases the most with the increasing dilution rate at frequency 5Hz and 10 Hz.Compared with the non-textured scheme,the average friction coefficient of the 30% dilution scheme decreases the most at frequency 5Hz and the value reaches 7.5-10.8%.It shows that the phenomenon of methanol diluted lubricating oil reduces the lubrication performance of the cylinder liner-piston ring,and the surface texture technology can reduce the friction loss of the engine to a certain extent,and achieve the purpose of improving the lubrication performance of key friction pairs in methanol engine.