Effect of Piston Skirt Profile Parameter on Secondary Motion and Lubrication Performance of Piston

doi:10.3901/JME.2018.15.100

Abstract

Abstract: The secondary motion of piston is modeled by considering the inertia of connecting rod according to the balance of the forces and moments acting on the piston. The influence of the structural parameters of the piston skirt longitudinal molded lines, the horizontal molded lines, the offset of piston pin and the thermal deformation on tribological properties of the piston skirt is investigated by considering coupling of the mixed lubrication of the piston-cylinder liner system and the dynamic behaviors of the piston. The average Reynolds equation of skirt lubrication is solved with FDM, and then the secondary motion trajectory of the piston is calculated by Runge-Kutta method. The influence of the piston skirt longitudinal molded lines, the horizontal molded lines, the offset of piston pin and the thermal deformation on the displacements and velocities of secondary motion, and friction power consumption is investigated by taking the inertia of the connecting rod, the surface roughness of the piston skirt and cylinder liner into consideration. The numerical results show that the inertia force of the connecting rod has important influence on the tribological property of the piston skirt. When the parabolic longitudinal molded line is applied for the middle-convex and varying ellipse piston, the amplitude and velocity of the secondary motion can be reduced. When the top and bottom ellipticities of the middle-convex and varying ellipse piston are chosen as smaller and bigger values respectively, the top and bottom radial reductions are chosen as smaller and bigger values respectively, the amplitude and velocity of the secondary motion can be also reduced. When the offset of piston pin is put to the thrust side slightly, the amplitude and velocity of the secondary motion can be also reduced. Meanwhile, the oil film thickness is increased, and the friction power consumption of the piston-cylinder liner system is reduced. The proposed model and numerical results can provide a theoretical direction to the design of piston skirt molded lines and further improvement of tribological properties of the piston-cylinder liner system.

Key words: piston skirt lubrication, secondary motion, The middle-convex and varying ellipse piston, thermal deformation

CLC Number:

TK401

LÜ Yanjun, LI Meng, ZHANG Yongfang, LIU Wanwan, YAN Dong. Effect of Piston Skirt Profile Parameter on Secondary Motion and Lubrication Performance of Piston[J]. Journal of Mechanical Engineering, 2018, 54(15): 100-116.

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