Effects of the connecting-rod-related design parameters on the piston dynamics and the skirt-liner lubrication

With the development of high-performance and high-speed engines, the effects that the connecting-rod-related design parameters have on the performance of the piston-liner system have become more important. Based on a new model of the piston dynamics presented by the present authors, the effects of the connecting-rod-related parameters on the side force, the oil-film thickness, the frictional force, and the piston dynamics are investigated. The results show that the changes in the extra transverse force and the piston's secondary motion are the main reasons for the different performances of the system. When the mass and the rotational inertia of the connecting rod are decreased, the extra transverse force is significantly reduced. When the location of the center of mass of the connecting rod is changed, the extra transverse force obviously changes in amplitude and trend. When the length of the connecting rod is increased, the amplitude of the extra transverse force increases during the upper half-stroke near the top dead center and decreases during the bottom half-stroke near the bottom dead center. Because of these changes in the connecting rod, the change in the extra transverse force leads to different behaviors of the side force, the minimum oil-film thickness, and the piston's secondary motion. However, changing the connection position of the connecting rod to the piston gives rise to very different behaviors of the piston's secondary motion, and the change in the piston's secondary motion generates significant differences in the minimum oil-film thickness. This study shows that the connecting-rod-related parameters are significant to the performance of the piston-liner system.