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.

Transient tribo-dynamic analysis of crosshead slipper in low-speed marine diesel engines during engine startup

“…In our previous study, we established a tribo-dynamic model that couples the dynamics of the crosshead assembly, piston assembly, and connecting rod with the crosshead slipper-guide and piston skirt-liner friction pairs. Under the engine rated conditions, an analysis of the tribo-dynamics of the crosshead slipper has been carried out [4,12,29,30]. In our previous study, the crankshaft speed was set to a fixed value.…”

“…Internal friction refers to the friction generated by various machines inside the ship, and external friction refers to the friction generated between the hull and the ocean. Research results have indicated that the friction loss of marine diesel engines is the primary source of internal friction [2][3][4]. To deal with a shortage of energy and environmental protection issues [5][6][7][8][9], the development of low-friction technology for marine diesel engines has become an urgent requirement of engine manufacturers.…”

“…The crosshead slipper-guide friction pair has an essential influence on the performance and life of low-speed marine diesel engines. The thrust force acting on the crosshead slipper leads to a large friction loss [4,12]. In addition, the transverse movement and swing (secondary motion) of the crosshead slipper Force of piston from bolt in Y direction also have an important influence on the vibration and noise of the engine [4].…”

“…The thrust force acting on the crosshead slipper leads to a large friction loss [4,12]. In addition, the transverse movement and swing (secondary motion) of the crosshead slipper Force of piston from bolt in Y direction also have an important influence on the vibration and noise of the engine [4]. Therefore, the performance of the crosshead slipper-guide system is a significant concern during the development of low-speed marine engines.…”

“…Considering the secondary motion of the crosshead slipper and coupling effects between the piston skirtliner friction pair and crosshead slipper-guide friction pair, the authors of this study established a more accurate tribo-dynamic model to analyze the performance of the crosshead slipper under the rated conditions [4,12]. Engines usually operate under complicated and variable operating conditions.…”