Study On The Tribological Properties And Lubrication Performance Of Ferrofluid In Piston Ring-Cylinder Liner System In Internal Combustion Engines

The piston ring-cylinder liner system is the most critical friction pair in the internal combustion engine,and its lubrication status directly affects the reliability and working efficiency of the internal combustion engine.Ferrofluid has excellent viscosity characteristics and magnetic responsiveness,it shows great potential value in the field of lubrication.This article will conduct research on ferrofluid in the field of tribology based on the rheological characteristics of magnetic fluid,and discuss its application in internal combustion engine pistons.Lubrication law and mechanism of ring-liner friction pair.In this paper,Fe₃O₄ nanoparticles were prepared based on the chemical co-precipitation method.After testing and characterization,the prepared Fe₃O₄ particles are pure phase,with an average size of 8-14 nm,and possess superparamagnetism.Subsequently,the magnetic fluid lubricating oil was formulated with oleic acid as a dispersant;the stability conditions of the magnetic fluid were deduced by the use of mechanical balance and the law of energy,and they were verified based on static experiments.At the same time,the viscosity experiment was carried out on the magnetic fluid and the viscosity prediction model of the magnetic fluid was deduced.Used ball-plated friction pair as experimental material,the tribological experiments of ferrofluid were carried out on the reciprocating machine.The influence of concentration,temperature,magnetic induction intensity and direction on the tribological characteristics of the ferrofluid was discussed.Experimental results show that compared with base oil,ferrofluid can significantly reduce the friction coefficient between the surfaces,and has obvious repair and protection effects on the wear and abrasion of the friction pair.The anti-wear and anti-friction effect of ferrofluid is more significant in a magnetic field.Based on the above research results,the lubrication experiments on the piston ring-cylinder system were carried out.Based on the Stribeck lubrication theory,the tribological behavior and lubrication state transfer process of base oil and ferrofluid under dynamic loading,temperature,frequency and starved lubrication conditions were discussed.The results show that in addition to reducing the average friction coefficient,ferrofluid can also delay the transition from mixed lubrication to boundary lubrication;under the effect of micro-bearing and deposited film,ferrofluid has a significant improvement effect on the lubrication of the engine under starved lubrication.Finally,based on the Reynolds lubrication theory and electromagnetic theory,this paper established the piston ring-cylinder liner ferrofluid lubrication numerical model for the first time,and analyzed its lubrication mechanism.The simulation results show that under the magnetic viscosity effect of the ferrofluid,the film thickness increase rate can reach up to 14.26%;because the magnetic field force shares the fluid load,the bearing capacity of the oil film has been better improved.The research work in this paper provides methods and guidance for the study of ferrofluid lubrication mechanism and its application in engine anti-friction and anti-friction.