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Influence of piston ring profiles and oil temperature distribution on cylinder liner lubrication of a marine two-stroke engine

A set of piston rings is used to form a dynamic gas seal between the piston and cylinder wall. Many physical phenomena are associated with the operation of the system piston-ring-cylinder (PRC), such as: inter-ring gas dynamics for the labyrinth seal, hydrodynamic lubrication and mixed friction in gaps between the rings and cylinder liner, oil flow and distribution of lubricant along the liner, twist motion of rings, liner temperature influence on the oil viscosity. The first part of the paper presents a complex model of the PRC system developed by the author. Among own models it includes several models taken from literature, like: a model of viscous oil flow between rough gap surfaces formulated by Patir & Cheng and an elastic contact model of Greenwood & Tripp. The main parts of developed complex mathematical model and software have been experimentally verified during a research period of the author at the marine engine designing centre ”Wärtsilä” in Switzerland. A relatively good qualitative and quantitative compatibility between the experimental measurements and calculated results has been achieved. In contrast to the previous papers of the author concerning the PRC system of combustion engines, new calculation results for a marine two-stroke engine have been presented. Firstly the right selection of barrel-shaped sliding surface of piston rings has been analysed. Secondly the influence of oil temperature distribution along the cylinder liner on the lubrication of the PRC system has been assessed. The developed model can be utilized for: evaluation of gas leakage through the sealing ring set, prediction of lubrication conditions of piston rings and oil consumption, defining areas of the possible cylinder liner wear and profile changes of piston rings sliding surfaces, and thus can be useful for optimization of the PRC system design. Key words: marine engines, piston rings, gasdynamics, hydrodynamic lubrication, mixed friction
Tematyka artykułu: Modelowanie i optymalizacja procesów w silnikach
Autor: Andrzej WOLFF, Ph.D., DSc.
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