Spontaneous process of dispersed salt water droplets in lubricant oil establishing wetted areas: Settling, spreading, coalescing and de-wetting

Abstract

Main shaft bearings determine aircraft engine's reliability and performance benchmark. Corrosion induced by salt water contamination in lubricant oil (SWCLO) is a big threat to bearing especially in coastal aircraft's engine. The recent progress in harm, purification and monitoring of SWCLO mixture contrasts the inadequate understanding about the critical process how droplet in SWCLO mixture is settled and distributed on bearing steel surface before corrosion occurrence. In present work, the complete processes towards reaching equilibrium states of single and multiple droplets were investigated. Hydrodynamic pressure involved model well predicts the overall falling of droplet over several millimeters. Smaller droplet has longer resting while faster spreading processes. Statistically, smaller droplet takes more time to be deposited accompanied by less probability, further smaller droplet keeps resting or drifting. There is a critical droplet size for deposition. Spreading induced coalescing causes droplet reshaping or de-wetting depending on causal and sessile droplet sizes. De-wetting indicates weakened corrosion. Spatial distribution of eventual sessile droplets is determined by deposition and coalescence at early stage of standing. These results are crucial for understanding, predicting and preventing aircraft engine's bearing corrosion from SWCLO mixture.