A Study of Piston-Ring Lubrication

Abstract

This paper describes an experimental study of the lubrication between a one-ring piston assembly and a cylinder. Instantaneous friction forces of the piston assembly were recorded by means of a special apparatus with a stationary piston and a reciprocating liner. Tests were carried out to determine the effects of viscosity, speed, and pressure on the friction, from which the oil film thickness under the ring was calculated. A suggested lubrication theory of piston rings is given, based on a balance of forces acting radially on the ring, leading to a theoretical formula for calculating the ring film thickness, which is in reasonably good agreement with the experimental results. Suggestions are made for the design of rings to give improved friction and heat transfer and to reduce cylinder wear, especially in the initial running-in period.