Tribology of piston compression ring conjunction under transient thermal mixed regime of lubrication

Fuel efficiency is the main IC engine attribute, with the compression ring-bore contact consuming nearly 5% of the fuel energy. Analyses are often idealised, such as isothermal condition and smooth surfaces, the former being particularly contrary to practice. An analytic solution to the average flow model is presented for this contact with a new analytical thermal model. The generated contact temperatures, particularly at the inlet result in thinner films than the idealised analyses. For the simulated city driving condition the power loss is mainly due to viscous shear under cold engine condition, whilst for a hot engine boundary friction dominates.

► Conjunctional heat balance is because of surface temperatures under normal engine conditions.
► Thermal balance is between combustion gasses and coolant channel flow, not contact transience.
► Unlike usual isothermal analyses, temperature significantly reduces the oil film thickness.