An Experimental Investigation of the Oil Film Lubricating Piston Rings

The minimum thickness of the oil film lubricating piston rings was measured successfully under motoring conditions by means of Eddy Current Sensors which were mounted on the liner. The measurements show the influences of engine speed, the viscosity of the oils and the profile of rings on their lubrication. The results also show the effects of hydrodynamic lubrication and oil starvation at the inlet of the rings. Under motoring condition, the minimum oil film thickness has no significant difference for the four strokes and it reaches a minimum value even though the rings are fully lubricated(without oil ring).