Development of a model capable of predicting the performance of piston ring-cylinder liner-like tribological interfaces

Friction in the piston ring package (piston, piston rings, and liner) is a major source of power consumption in large two-stroke marine diesel engines. In order to improve the frictional and wear performance, knowledge about the tribological interface between piston rings and liner is needed. The work described in this article addresses the subject from both an experimental and a theoretical perspective. First, a one-dimensional numerical model based on the Reynolds equation is presented. It uses a pressure-density relation for the modelling of cavitation. The viscosity is assumed to depend on a measured temperature only; thus, it is not necessary to include the energy equation. Conservation of oil is ensured throughout the domain by considering the amount of oil outside the lubricated interface. A model for hard contact through asperities is also included. Second, a laboratory-scale test rig is described. Results from a number of experimental tests with different geometries and running speeds are presented. Finally, a comparison between the measured friction force and simulated values is given. Good correlation between the measurements and the simulations has been observed, especially when running at a high speed. This article represents the first steps in the pursuit of being able to accurately model the interface between a piston ring and the cylinder liner in large two-stroke diesel engines.