A new comprehensive tribo-dynamic analysis for lubricated translational joints in low-speed two-stroke marine engines

Abstract

In low-speed two-stroke marine engines, the effect of connecting rod inertia is important for the tribo-dynamics of crosshead slipper-guide and piston skirt-liner. However, this has not been considered in previous research. Therefore, a new tribo-dynamic model that considers the connecting rod inertia is presented for the two lubricated translational joints, and the lubricant viscosity–temperature properties are accurately incorporated into the model. The modified extended backward differentiation formulate method is used to solve the nonlinear stiff differential equations effectively. The simulation results show that the effect of connecting rod inertia on the dynamic characteristics of two translational joints is mainly observed during the latter half of the upward stroke. For the crosshead slipper, the amplitude of the transverse velocity is increased by 30% at a crank angle of approximately 300° compared to the early model that ignored the connecting rod inertia. With the increase of the connecting rod mass, the secondary motions of both the crosshead slipper and the piston skirt are increased. Furthermore, a decrease of the connecting rod mass can reduce the friction losses of the engine.