Study on the Mixed Lubrication of Piston Rings in Internal Combustion Engine

The oil-film thickness between piston ring and cylinder liner in an internal combustion engine is conventionally predicted by the hydrodynamic lubrication theory. The predicted value of minimum oil-film thickness is comparable to or smaller than surface roughnesses of the piston ring and cylinder liner. In the present study, the theoretical analyses are conducted in order to evaluate the oil film and friction characteristics of the piston rings operating in the mixed lubrication regime. The average Reynolds equation based on the average flow model is used. The asperity interaction is also taken into account to obtain hydrodynamic and non-hydrodynamic components of load acting on the piston ring. The results show that the friction spikes at both ends of the stroke are very sensitive to the surface roughness.