Testing Research On Friction Wear And Numerical Simulation Of The Friction Lubrication Based On LBM Method Of Diesel Engine Piston Ring-Cylinder Liner

The friction loss of the piston ring-cylinder liner system is the main source of mechanical loss in the internal combustion engine.The working environment of the piston ring-cylinder liner friction pair is bad,and it is affected by factors such as high temperature,high pressure and high engine speed.It has great friction loss and wear due to poor lubrication.At the same time,with the widespread application of diesel fuel post injection technology,the problem of lubricating oil being diluted by fuel is becoming more and more serious,which will further worsen the friction and lubrication condition of the piston ring-cylinder liner system.Therefore,it is especially important to study the tribological performance of piston ring-cylinder liner under the influence of various factors.Firstly,the real-time friction coefficient and surface three-dimensional shape,which are obtained by SRV-V friction and wear tester along with White-light interferometric surface profilometer,are adopted as the indexes for the evaluation of the friction and wear performance at the conditions same as those at the top dead center(power stroke)in a diesel engine.The test results show that in the one-hour test,the friction coefficient between the second piston ring and the cylinder liner rises rapidly in the first stage,gradually decreases in the second stage,slowly increases in the third stage,and tends to stabilize in the fourth stage.The friction coefficient is finally stabilized at a value between 0.144 and 0.145.After the test,the surface contour height of the piston ring is significantly reduced,and the taper is slowed down.Secondly,with the real-time friction coefficient and wear amount as indicators,the piston ring-cylinder liner friction and wear test under the conditions of variable temperature,variable load and variable lubricating oil dilution ratio were carried out.The test results show that the friction coefficient decreases first and then increases with the increase of temperature.At high temperatures,the lubricating oil is unstable and the friction coefficient suddenly rises to a high value.The friction coefficient decreases first and then increases with the increase of the load.The high load also causes the change of the lubricating oil property,leading to a sharp increase in friction coefficient.A small amount of diesel dilution can greatly reduce the viscosity of the lubricating oil,resulting in a larger frictioncoefficient and wear than the original lubricating oil condition,but the friction coefficient and the wear amount will decrease as the dilution ratio is further increased.Finally,the friction lubrication model of the axial structure of the piston ring cylinder liner based on the lattice Boltzmann method is established based on MATLAB software and the effectiveness of the model is verified by the finite difference method.The effects of piston ring speed,lubricating oil viscosity,lubricating oil temperature and piston ring taper on the friction lubrication performance of the piston ring-cylinder liner friction pair are analyzed and calculated.The calculation results show that the dynamic pressure effect between the piston ring and the cylinder liner becomes more obious with the increase of the piston ring speed and the viscosity of the lubricating oil;the friction and load between the piston ring and the cylinder liner decrease with the increase of the lubricating oil temperature,but this change trend becomes slower with the gradual increase of the temperature.The increase in the taper of the piston ring has a friction reducing effect,and the frictional force decreases as the taper increases,but the decreasing tendency becomes gentle as the taper gradually increases.