A tribological analysis on stuffing box-piston rod system of low-speed marine diesel engines

The stuffing box-piston rod system is widely used in the low-speed marine diesel engines to scrape oil and ensure sealing. Its friction power loss and wear rate are great, but the studies about the system are very limited. In this study, based on the special structure and working conditions of the stuffing box, the analytical model for the tribological properties of the stuffing box-piston rod system is developed considering the oil starvation and relative ring location effects. The minimum oil film thickness, friction, oil transportation, and asperity contact are calculated for the stuffing box. The analysis results show that compared with the fully flooded lubrication, the minimum oil film thicknesses of the rings reduce significantly in the middle of the strokes under the starved lubrication condition, but the friction losses of the rings are influenced by the comprehensive effects of the oil film thickness reduction and lubricating area reduction under the starved lubrication condition, which is related to the specific profiles of the rings. In addition, compared with the engine piston ring pack, the relative ring location effect is more obvious in the stuffing box ring pack because there are more rings and the ring intervals are larger. The relative ring location effect makes the minimum oil film thicknesses, friction forces, and asperity contacts of the rings have oscillations after bottom dead center and top dead center.