Numerical simulation of combustion-driven oil transport on the top land of an internal combustion engine piston

Abstract

A mathematical model of a lubricant film attached to the top land of an internal combustion engine piston was formulated. Multidimensional oil transport induced by gas flows within the top land crevice was included in the model, with the intention of predicting the effects of such gas flows on top land carbon deposits. A finite-volume, shock-capturing simulation of the film's free surface was created, and its accuracy verified. Preliminary results were generated using crevice gas flow data taken from a separate computational fluid dynamics (CFD) simulation of a modern diesel engine's combustion process. It was found that combustion-driven gas flows within the top land crevice can have a profound effect on the top land oil film thickness distribution. A fundamental lubricant transport mechanism arising from an interaction between the effects of the engine's reciprocating inertia and those of the gas flow-induced shear forces was discovered. For the engine studied in the present work, the mechanism severely reduced the amount of lubricant in some regions of the top land. An engine designe's clever usage of this mechanism could potentially reduce both oil consumption and top land carbon deposits.