Molecular dynamics investigation of a model ionic liquid lubricant for automotive applications

TL;DR

This study uses coarse-grain molecular dynamics to model ionic liquid lubricants in piston ring-cylinder contacts, revealing two lubrication regimes and behaviors that could prevent wear in automotive engines.

Contribution

Introduces a novel mesoscopic modeling approach for ionic liquid lubricants with variable confinement, capturing lubrication regimes and force behaviors relevant to automotive applications.

Findings

Identified elasto-hydrodynamic lubrication at low loads.

Discovered low, velocity-independent friction at high loads.

Observed steep normal force increase at small gaps.

Abstract

In the current work we present a new modelling approach for simulating meso-scopic phenomena related to lubrication of the piston ring-cylinder liner contact. Our geometry allows a variable confinement gap and a varying amount of lubricant in the gap, while avoiding the squeeze-out of the lubricant into vacuum. We have implemented a coarse grain molecular dynamics description of an ionic liquid as a lubricant which can expand into lateral reservoirs. The results have revealed two regimes of lubrication, an elasto-hydrodynamic one under low loads and one with low, velocity-independent specific friction, under high loads. The observed steep rise of normal forces at small plate-to-plate distances is an interesting behaviour that could potentially be exploited for preventing solid-solid contact and wear.