CFD Modelling of Three-component Air/Oil Flow and Heat Transfer in a Rotating Annulus

摘要

Numerical calculations using an Eulerian modelling approach, are performed to study the flow and heat transfer behaviour of turbulent, steady, two-dimensional, two-phase, three component flow (air, oil film and oil droplets), within an annular region representative of a section of an aero engine bearing chamber. The primary aim of the work presented is to identify whether an Eulerian approach to the air/oil flow in a bearing chamber is capable of yielding useful results. Oil droplets in the core air flow are modelled as a dispersed phase and a particle drag model is used to calculate interphase momentum transfer. Air and liquid oil are modelled as continuous phases and in this case a mixture model is used to calculate the interphase momentum transfer. Results are presented showing the spatial variation in chamber temperature and volume fraction as a function of mean droplet diameter, for two representative diameters of 10 μm and 100 μm. The results obtained are very sensitive to droplet diameter, indicating the need for accurate input data when using this modelling approach. The effect of shaft speed on oil volume fraction and chamber temperature profile was investigated for shaft speeds in the range 100 rad/s to 733 rad/s. At higher shaft speeds the oil film is thinner and the temperature slightly increased near the outer cylinder. The Eulerian approach to two-phase, three-component flow modelling has yielded plausible results for the annulus and warrants further investigation as an approach to model bearing chamber flow and heat transfer.