Analysis Of Lubrication Characteristics And Oil Film Thickness Test Of Diesel Piston Components

The piston assembly is part of the core components of the internal combustion engine.The quality of the lubrication between the piston assembly and the cylinder liner will directly affect the economy and reliability of the internal combustion engine.In this paper,lubrication performance of piston components(piston skirt and piston ring group)is studied from both theoretical and experimental aspects.The theoretical research part is built on YTRC2110 D four-stroke diesel engine.When the piston ring contacts the ring groove,the second-order movement of the piston will affect the lubrication performance of the piston ring.Therefore,lubrication performance between the piston skirt and the cylinder liner was first studied,and a comprehensive model including piston dynamics,tribology,and micro-convex contact was established.The analysis of the second-order motion of the piston,the knocking face of the corner of the piston,the thickness of the lubricant film between the piston skirt and the cylinder liner,and the friction loss work is realized.Then the speculative study of the lubrication performance of the piston ring group was carried out.Considering the effect of the second-order movement of the piston on the lubrication performance of the piston ring,a comprehensive model including the dynamics,tribology,and gas flow state of the piston ring group was established to achieve the minimum oil film thickness and friction between the piston ring group and the cylinder liner Analysis of work loss,crankcase blow-by volume,and axial movement of piston rings in ring grooves.In the experimental verification separate,the engine test bench was modified,and the thickness of the oil film between the top ring and the cylinder liner of the YTRC2110 D diesel engine was measured using the ultrasonic method.This experiment uses an ultrasonic transmitting and receiving device to send and receive ultrasonic longitudinal wave pulse signals,using an ultrasonic transducer to complete the conversion of pulse signals and ultrasonic signals,and attaching an ultrasonic sensor on the outer wall of the cylinder liner to inject the ultrasonic signals into the cylinder liner-Oil film-piston ring in three layers of media,and then use a computer for filtering and signal processing.The measurement results in this experiment clearly reflect the distribution law of the oil film thickness between the top ring and the cylinder liner,and they agree well with the simulation results,which prove the correctness of the model established.Finally,using the established piston assembly(piston skirt and piston ring group)lubrication performance analysis model,a diesel engine is taken as an example for case analysis.The effects of piston pin offset,piston center of gravity offset,and cylinder clearance on piston skirt lubrication performance were studied.And the impact of the position of the bump in the piston ring,the effective lubrication length and the height of the barrel surface on the lubrication performance of the piston ring.Orthogonal tests were carried out to optimize the profile of the piston ring and improve the lubrication performance of the piston ring.