Study On The Working Characteristics Of Piston Ring Assembly Of Marine Four-stroke Diesel Engine

As one of the core components of the diesel engine,piston ring has the function of sealing the gas in the combustion chamber,controlling the distribution of lubricant,transmit combustion heat and supporting the piston.The optimized design of the piston ring shape can further reduce the gas leakage volume in the cylinder,reduce the friction loss of the diesel engine,control the consumption of lubricant,and on this basis,improve the efficiency of the diesel engine.In this paper,taking the 4L20 diesel engine as the research object,the dynamic model of the piston ring group was constructed,and the influence of the working condition of the piston ring group and the parameters of piston ring shape on the gas leaking into crankcase,friction loss and lubricant consumption during the operation of the diesel engine was studied,based on which,the piston ring shape was optimized.Research work was conducted from the following aspects in this paper:(1)The operation data of the 4L20 diesel engine under different load conditions of 1000 rpm was calculated through measurement.The thermal deformation analysis of the piston and the cylinder liner was.conducted,the radial stiffness analysis of the piston was completed,and in the end,the piston ring-cylinder liner dynamic lubrication simulation model was established.(2)The operation status of the piston ring during the operation of the 4L20 diesel engine was obtained,which suggests that the total friction loss of the outer working surface of the first gas ring,the second gas ring,and the oil ring decreased orderly,with the average values being 2.49kW,1.07 kW and 0.72 kW respectively.The average value of the gas of one gas cylinder leaking into the crankcase was 3.67m3/h,and the average value of the oil slinging volume by inertial force of the entire working cycle was 1.79 g/h.(3)Targeting at the structural parameters of the first gas ring,the second gas ring,and the oil ring,the influence rules of each parameter on the gas leakage,friction loss of the outer working surface of the piston ring,and the oil slinging volume by inertia force were analyzed.(4)The shapes of the first gas ring,the second gas ring,and the oil ring were changed respectively,the changes of the piston ring working conditions after changing each parameter were studied,and after considering their coupling effects,final optimization shape of piston ring was determined.The three piston rings were optimized simultaneously,after which,relative low reduction in the friction loss of the outer working surface of the first working ring and the oil ring and the gas leaking into the crankcase were witnessed,with the average value being reduced from 2.49kW,0.72 kW,3.67m3/h to 2.45 kW,0.60 kW,3.51 m3/h.There were significant reductions in the friction loss and oil slinging by inertial force of the second gas ring,and the average value decreased from 1.07 kW and 1.79 g/h to 0.79 kW and 0.65 g/h,respectively.