How Do Interfacial Shear and Gravity Affect the Oil Film Characteristics Near an Aero-Engine Bearing?

Abstract

Recent demand for reducing carbon emission and for increasing engine efficiency has led aero-engine manufacturers to strive for a better oil flow system. Aero-engine bearing chambers that house the shaft-support bearings are among the most challenging parts of the engine systems and it is imperative to have a proper understanding of the oil flow characteristics inside a bearing chamber to increase the engine efficiency. The present work is focused on experimentally investigating the oil film characteristics near a ball bearing static slot in the co- and counter- current regions at various rotational Reynolds number (Reω), loads and liquid flow rates. The experimental investigation has been carried out over a wide range of engine relevant Reω up to 1.7×106 using high-speed imaging and a long distance microscope. The results show that formation of the oil film on the static elements of the bearing is governed by both gravity and interfacial forces at low Reω but only governed by interfacial forces at high Reω. The nondimensional film thickness ranged from 0.71 to 0.18 and decreases with increasing Reω. A regime map was obtained based on the waviness of the film interface showing three different types of wave. At all conditions investigated all waves were capillary waves. Reω, oil flowrate and gravity were found to have a significant effect on the film thickness (δ) with transitions matching the wave regime map.