Simulation of a Simplified Aeroengine Bearing Chamber Using a Fully Coupled Two-Way Eulerian Thin Film/Discrete Phase Approach Part II: Droplet Behavior in the Chamber

Abstract

Within aeroengines, bearing chambers exhibit a highly complex two-phase environment as a result of the complex air/oil interactions. The desire to operate at both higher temperatures and shaft speeds requires a sufficient understanding of these systems for design optimization. Typically, bearings are used to support the radial and axial loads transmitted by the shafts and require oil for lubrication and cooling. These bearings are housed in bearing chambers that are sealed using airblown seals. Efficient scavenging systems ensure that the oil is collected and returned to the tank avoiding any unnecessary working of the oil. Previous work at the Gas Turbine and Transmissions Research Center (G2TRC) has highlighted the need for an adequate computational model which can appropriately model the oil shedding behavior from such bearings. Oil can breakup forming droplets and ligaments, subsequently forming thin and thick films driven by both gravity and shear. The objective of this paper is to explore the modeling capability of fully two-way coupled Eulerian thin film/discrete phase models (ETFM-DPM) applied to our simplified bearing chamber configuration. The models are created using openfoam and two-way coupling is employed, enabling Lagrangian droplets to either impinge on the film surface or be removed through effects such as film stripping, splashing, or edge separation. This paper focuses on the droplets, presenting statistics relating to size, velocity, impingement, and residence time, and provides insight into solution sensitivity to operational parameters including shaft speed and oil flow rate. This extends upon our previously published work and improves bearing chamber modeling capability.