Friction And Lubrication Research On Typical Friction Pairs In Internal Combustion Engine Based On Cavitation Theory

Plain journal bearing and piston ring/liner are two typical friction pairs in internalcombustion engine. Lubrication peformance of plain journal bearing directlydetermines a series of parameters such as its bearing capacity, friction, reliability andlifetime. Lubrication peformance of piston ring/liner has great influence on frictionloss, wear of piston ring and cylinder liner, blow-by, lubricant consumption andparticulate emission in internal combustion engine.Therefore, this article firstly carriesout study of pain journal bearing lubrication and piston ring/liner lubrication in depthand in detail by theoretical research, considering the macro cavitation andinter-asperity cavitation. Then, friction coefficient of reciprocating section cut fromactual piston ring and cylinder liner is analyzedIn misaligned plain journal bearing lubrication research, the cavitation modelproposed by previous researchers is adopted and lubrication analysis software isprogrammed in Matlab. Then the influence of the macro cavitation and inter-asperitycavitation on the lubrication properties such as oil film pressure distribution, oildischarge at the bearing end, oil film moment and oil film bearing capacity isanalyzed, which is of great use when one chooses the reasonable calculation model.Also, cavitation of plain journal bearing at different misaligned angles is analyzed.The results show that cavitation happens to great extend at low pressure area whenbearings are in the running process, and inter-asperity cavitation can also lead to thechange of lubrication at the cavitation boundaries. Both kinds of cavitation greatlyinfluence lubrication peformance and cannot be ignored.As for piston ring-liner lubrication research, first of all, unified lubrication controlequation is established based on the control volume mass conservation principle,considering cavitation effect and the new method Newton-Raphson method isproposed to solve the model. And cavitation effect on lubrication performance isanalyzed. Secondly, based on the macro cavitation analysis and the Patir and Cheng’s"average" thought, the average lubrication control equation is established, consideringthe influence of inter-asperity cavitation, and inter-asperity cavitation on lubrication performance is analyzed. The results show that, the new numerical method is effectivewhen it is used to analyze the lubrication performance of piston ring-cylinder. Macrocavitation has great effect on lubrication performance, while inter-asperity cavitationis also an indispensable part in lubrication analysis. A comprehensive consideration ofmacro cavtation and inter-asperity cavitation tends to be of significance in accurateanalysis of lubricationIn the experimental research of piston ring-cylinder, the friction coefficient in acycle of the reciprocating motion is measured on the bench SRV○R4. The variation ofthe friction coefficient in a cycle and influence of load, frequency, stroke andtemperature of lubricant on the friction coefficient is studied. The results show thatfriction coefficient changes as speed varies with time and is influenced byload,frequency, stroke and temperature of lubricant.