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

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.