A Study On the Oil Film Thickness Between the Lower Rail of Oil Control Ring and Lower Flank of Oil Control Ring Groove of an Engine

Lubricating oil consumption (LOC) of engines causes particulate matter in exhaust gas and abnormal combustion like pre-ignition which becomes a serious problem in hydrogen engines. Lubricating oil transports upward into the combustion chamber of an engine via the sliding surface, the gap, and the side and back of a piston ring. The target of this study was clarifying the mechanism of oil flowing between an oil control ring lower flank and the groove which was the first entrance of lubricating oil supplied from the crank shaft. Oil film thickness at the lower flank of the oil control ring was measured by laser induced fluorescence method using optical fibers embedded in the lower flank of the ring groove. The measured oil film thickness was compared with forces acting on the lower rail of three-piece type oil control ring. The oil film thickness change was well explained using those forces and it was found that friction force at the sliding surface and pressure in the ring groove were dominant on the oil film thickness under all operating conditions tested in this study.