| The cylinder liner and piston ring are one of the most crucial friction pairs in the internal combustion engine,and the lubrication and friction properties of cylinder liner and piston ring affects the fuel efficiency,system durability and even the life of internal combustion engine directly.With the internal combustion engine moves toward high-power density and low fuel consumption,the engine pressure and temperature increase significantly,which leads to a worse condition for cylinder liner and piston ring.Thus,improving fuel efficiency and prolonging the service life of cylinder liner and piston ring is of vital significance in the development of a modern internal combustion engine.During the operation of the internal combustion engine,an excellent performance lubricant is a critical factor for its regular and stable operation,and the main factor determining the performance of the lubricant is the type and content of additives in the lubricant.Although various traditional lubricating oil additives containing sulfur,phosphorus,zinc and other elements can still fulfil service conditions such as extreme pressure,high speed and high temperature,they are far fiom the requirements of environmental protection regulations.Filtration conversion can hardly meet the current national energy conservation and emission reduction standards.Therefore,many researchers in the world are working on the development of new and environmentally friendly lubricant additives.With the emerge of nanomaterials,the quantum size effect,small size effect,interface and surface effects of nanomaterials have been widely studied.Nanomaterials have opened up new fields for industrial materials with their unique physical and chemical properties.Existing studies have shown that when specific nanoparticles added as lubricants to lubricants,they can have unexpected lubrication effects on friction pairs,especially in harsh environments such as heavy loads,high temperatures,high speeds and heavy pollution.Based on nano-materials as lubricant additives,they have an excellent anti-friction and anti-wear effect.The primary and applied research on the application of nano-materials in the development of lubricant additives has become an important direction of current research.Many studies have been carried out,and many representative results have been obtained.Based on the current research results,this article selects nano-diamond particles as lubricant additives.It explores their tribology properties against the base oil between the cylinder liner and the piston ring.The results obtained were as follows:1.Polyaniline/nano-diamond(PANi/ND)composites were prepared using "Polyaniline in-situ polymerization and dispersion of nano-diamond particles",and the prepared PANi/ND composites were characterized using SEM,TEM and XRD material characterization equipment.Understand the morphology and dispersion state of the binary hybrid structure,and then use the ultrasonic dispersion method to stably 'disperse the composite material into a base oil to prepare a nano-diamond lubricant,so that the nano-diamond particles coated with polyaniline can stably be suspended in the base oil.No obvious delamination and diamond particle deposition were observed at room temperature for at least 15 days,which can be used for subsequent evaluation experiments2.To simulate the boundary lubrication state of the cylinder liner-piston ring system at the top dead center of the stroke in a real internal cofnbustion engine,the reciprocating sliding tribo-tester developed and designed by the research group.The stepwise load test results show that that nano composite lubricant can significantly improve the extreme pressure performance and anti-wear performance of base oil between specific friction pairs.The optimal concentration of nano compound lubricant between the friction pairs of nitriding cylinder liner-PVD piston ring is 2wt%,and that between the friction pairs of.chromium cylinder liner-PVD piston ring is lwt%.However,for cast-iron cylinder liner-PYD piston ring,nano compound lubricant has no friction reducing effect,even increases wear.3.In order to evaluate the high temperature resistance of nano composite lubricant,the long-time wear test method was selected for evaluation.The results show that nano diamond lubricating oil can reduce the friction coefficient between the cylinder liner-piston ring,especially improve the anti-friction performance of the base oil at higher temperature.At high temperature(200?),the friction coefficient between nitriding cylinder liner-PVD piston ring is lower than that of base oil 12%,19%and 15%respectively.However,under the 200?,the surface of chromium cylinder liner is abnormally worn under the condition of base oil lubrication,and the friction fluctuation range is large,so it is impossible to calculate the friction coefficient.In the meanwhile,the other three groups of friction pairs can operate stably under the condition of nano composite lubricant,without abnormal wear4.The effect of different concentration of nano compound lubricant on the anti-scuffing performance of the base oil was studied.The results show that the nano composite lubricant can improve the anti-scuffing performance of the base oil between the nitriding cylinder liner-PVD piston ring and the chromium cylinder liner-PVD piston ring,especially in the chromium cylinder liner-PVD piston ring.When the high-load running in is 20MPa,the average anti-scuffing time of the three groups of nitriding cylinder liner-PVD piston ring friction pairs is 131min,156min and 120minss.Compared with the base oil,the anti-scuffing time is increased by 2.3 times,2.8 times and 2 times respectively.At the same time,the average anti-scuffing time between the three groups of chromium plated cylinder liner-PVD piston ring friction pairs is 175min,130min and 160min respectively.Compared with the base oil,the anti-scuffing time is 175min,130min and 160min.the anti-scuffing time is increased by 7 times,5.2 times and 6.4 times respectively. |
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