The Basic Experimental Research Of Nano-lubricants For Improving The Lubrication And Friction Properties Of Piston Ring And Cylinder Liner Of Internal Combustion Engine

The cylinder liner and piston ring is one of the most crucial friction pairs in the internal combustion engine,and the lubrication and friction properties of piston ring and cylinder liner affects the fuel economy,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 piston ring and cylinder liner.Thus,improving fuel economy and prolonging the service life of engine are of vital significance in the development of modern internal combustion engine.Series of studies have indicated that the nanoparticles as lubricant additives can improve the tribological behavior of lubricant significantly.As a new lubricant,nano-lubricants have attracted increasing attention in the field of engine tribology.In this study nano-Cu particles,nano-SiO₂ particles and nano-fullerene particles were used as the additives of base oil,the tribological properties were investigated by extreme pressure test,antiwear and friction reducing test and varying operating condition test.The morphology of the worn surfaces were observed by FE-SEM,and the lubrication mechanisms of nano-lubricants were analyzed.The materials of nano-lubricants which is suitable for the real internal combustion engine and can't cause secondary pollution were discussed in the end.The specific contents of this study were as follows:?1?The nano-lubricants were prepared by dispersion method and suspension stability were analyzed accordingly.The viscosity characteristics of nano-lubricants were analyzed by viscometer.?2?The extreme pressure properties and antifriction properties of nano-lubricants were investigated by the four-ball tester,which reproduces the mixed lubrication around the top dead center and the hydrodynamic lubrication away from the top dead center respectively.And the comparison of tribological behavior of three kinds of nano-lubricants at the same concentration were studied at the same time.The worn surfaces were observed by FE-SEM,and the lubrication mechanisms of three kinds of nano-lubricants were deduced based on the experimental observations.The possibility of nano-SiO₂ lubricants which is applied in the real internal combustion engine were argued according to the experimental results of extreme pressure test,antiwear and friction reducing test.?3?In order to simulate the patterns of movement,contact form,operating condition and lubricating condition of cylinder liner and piston ring in the real engine,the Nano-SiO₂lubricant and real piston ring and cylinder liner materials were used to evaluate the lubrication and friction properties investigated on a contraposition reciprocating test rig under varying operating conditions?change the temperature,speed and the load?,which reproduces the patterns of movement?reciprocating movement?,contact form?surface contact?and lubricating conditions between piston ring and cylinder liner around the dead center of internal combustion engine.The morphology of the worn surfaces of cylinder liner were observed by FE-SEM,and the frictional mechanism of nano-SiO₂ lubricants in varying operating condition test was analyzed.