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

Abstract

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 bearings. Oil can break up forming droplets and ligaments, subsequently forming thin and thick films driven by both gravity and shear. Our previously published work using openfoam successfully coupled the Eulerian thin film model (ETFM) with the discrete phase model (DPM) (Nicoli et al., 2019, “A New OpenFOAM Solver Capable of Modelling Oil Jet-Breakup and Subsequent Film Formation for Bearing Chamber Applications,” ASME Paper No. GT2019-90264.). In this paper, the previously developed ETFM-DPM capability is, for the first time, extended to an aeroengine representative bearing chamber configuration. The configuration matches that of a simplified aeroengine bearing chamber that has been investigated by researchers at the Gas Turbine and Transmissions Research Center (G2TRC). Numerical investigations are conducted for three different shaft speeds, namely, 5000, 7000, and 12,000 rpm, at two different oil flow rates: 7.3 liters/minute and 5.2 liters/minute. CFD results are validated against existing experimental data for the two lower shaft speeds. Evaluation of computed mean film thickness shows excellent agreement with the experimental data. Results show that there is a diminishing reduction of film thickness with an increasing shaft speed. The computational study allows investigation of oil residence time in the annulus near the bearing. Residence time is seen to reduce with increasing shaft speed and with increasing oil flow rate. This CFD investigation represents the first successful fully coupled two-way ETFM-DPM investigation into the droplet generation process within a bearing chamber application, establishing a firm foundation for future aeroengine bearing chamber modeling.