Research On The Lubricant Oil Transportation And Lubrication Between The Piston Assembly And The Cylinder Liner Of Internal Combustion Engines

Studying on the piston assembly—cylinder liner lubrication plays an extremely important role in the design of an internal combustion engine.At present,most of researches select the full lubrication condition or some special boundary condition,which fail to consider of the lubricant oil flowing around the piston ring or the piston skirt along with its effect on the boundary condition of lubrication analysis.The lubricant oil supply is the key factor for determining the lubrication condition.In researches the boundary condition is to be set according to the analysis of lubricant oil flowing around the piston ring or the piston skirt,which can leads to true lubrication character of frictional pair,and provides reliable proof for engine design.This paper takes a four strokes internal combustion engine as the object.Based on the lubricant oil flowing in the piston assembly-cylinder liner system and the impact on oil supply to the friction pair,the boundary condition is set as proceeds lubrication numerical analysis of piston rings and piston skirt.The lubricant oil transportation and consumption is researched as well.All researches are summarized mainly as following.Firstly,regarding the piston skirt,the lubricant oil is checked to supply to the area between it and the cylinder liner according to the splashing oil to the surface of cylinder liner.With solving the basic equation and the Second motion equation of piston,the lubrication performance as minimum oil film thickness,the maximum oil film pressure,the asperity contact force,the frictional force and frictional power is obtained.Whether the variety of engine load or the changing of engine speed influences the lubrication performance of piston skirt as well as the oil transportation.Then,the oil control ring,the scraper ring and the compression ring are studied respectively.The oil control ring with the lubricant oil flowing by was analyzed beginning with the structure dissected.The minimum oil film thickness,the maximum oil film pressure,the asperity contact force,the frictional force and frictional power are calculated.The change of lubricant oil quantity in the piston land area above the oil control ring is studied as well as the oil transportation to the top dead center controlled by the oil control ring.The result shows that the minimum film thickness and the oil film pressure are bigger,and the frictional force and frictional power are smaller in the middle of strokes,than those near the top dead center or the bottom dead center.The oil control ring is the key part to govern the oil sending to the top dead center.The minimum oil film thickness was checked for the scraper ring based on the structure as well as other performance respectively in each stroke.The lubricant oil flows through the scraper ring was also calculated.With the asymmetry structure,the quantity of oil flows through the scraper ring in the up-stroke is much more than that in down-stroke.Under different running condition and inner film thickness,the minimum oil film thickness and other lubrication performances of compression ring were studied.The performance of compression rings varies in respective rule with engine operating condition change or varied inlet oil film thickness.Thirdly,regarding the composition of the oil control ring and the scraper ring and the compression ring,the analysis of lubricating oil flow in the piston assembly of internal combustion engine was done.The lubricant oil evaporation on cylinder liner was studied.Based on the lubricant oil flow,the lubricating oil quantity between the scraper ring and the compression ring is calculated.The residual lubricant film thickness on cylinder liner surface after the compression ring passing through in a down-stroke and the inlet oil film thickness of compression ring in the following up-stroke were made certain of.The lubricating characteristics of the scraper ring-cylinder pair and the compression ring-cylinder pair were analyzed.Comparing with the full lubrication,the rings’ performances are serious different with those of the actual lubrication in the ring pack considering of lubricant oil flow.The oil transportation affects the lubrication performance of the ring in the ring pack.The consumption of lubricant oil is studied by numerical simulation and experiment respectively to illustrate the relationship between the oil transportation and lubrication.The result shows that the oil consumption rises when the engine load increases.