Bearing chambers in an aero-engine are designed to provide specialised compartments where bearings may be supported to locate the shaft systems. The design of the bearing chambers, including sealing and oil system integration, is vital to the performance and reliability of aero-engines and hence it is of great significance to gain better understanding on the two-phase air/oil flow behaviour within the chambers. The physical phenomena occurring within the bearing chambers involve the interaction of turbulent airflow and oil in the form of jets, droplets and films. This paper reports two-way coupling CFD calculations for turbulent airflow and oil droplet motion in an aero-engine bearing chamber geometry in order to assess the influence of the interaction between airflow and oil droplets on the air flow and droplet impingement locations. In the CFD calculation the airflow is assumed to be incompressible and isothermal and the airflow motion is driven by rotating shafts and described by a standard k-ε turbulence model as implemented in the commercial CFD package CFX 4.2. The oil injected to the chamber is assumed to be in the form of discrete droplets and subsequent droplet motions are modelled using a Lagrangian tracking method. Turbulent dispersion and interaction between droplets are not included. The calculations are carried out at shaft speeds corresponding to a representative flight state with droplet diameters in the range of 1–500 microns. The CFD model of the bearing chamber used has a total cell number of 405,500 and the grid is constructed to ensure that the wall function formulation used at the boundaries for the turbulence model is valid. The boundary conditions within the chamber are specified by prescribing velocity conditions on chamber surfaces corresponding to the rotating components. The calculations are iterative; for the airflow, an additional source term, due to the drag forces from droplets, is added to the governing equations. The droplet trajectories are then simulated based on the updated airflow field. It is found that many major features of the airflow field obtained using the two-way coupling method are similar to those obtained using the simpler one-way coupling method. However, significant localised differences exist between the airflow fields obtained using the one-way and two-way coupling methods where the interaction of oil droplets with the airflow is more intense. There are localised regions in the vicinity of the oil injection where the oil droplet motion leads to an increased airflow speed. The motion of small droplets is differentially influenced by any change in airflow characteristics predicted using the two-way coupling method due to their small inertia and consequently the deposition characteristics of the small droplets are different. However, large droplets are less influenced by the modest change in the airflow and no significant difference is calculated in the deposition locations of oil droplets provided that droplet diameters larger than 100 microns are considered.
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ASME 2002 Pressure Vessels and Piping Conference
August 5–9, 2002
Vancouver, BC, Canada
Conference Sponsors:
- Pressure Vessels and Piping Division
ISBN:
0-7918-4659-8
PROCEEDINGS PAPER
Numerical Study of the Two-Phase Air/Oil Flow Within an Aero-Engine Bearing Chamber Model Using a Coupled Lagrangian Droplet Tracking Method
Kathy Simmons,
Kathy Simmons
University of Nottingham, Nottingham, UK
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Stephen Hibberd,
Stephen Hibberd
University of Nottingham, Nottingham, UK
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Ian Care
Ian Care
Rolls-Royce plc, Derby, UK
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Kathy Simmons
University of Nottingham, Nottingham, UK
Stephen Hibberd
University of Nottingham, Nottingham, UK
Yi Wang
University of Nottingham, Nottingham, UK
Ian Care
Rolls-Royce plc, Derby, UK
Paper No:
PVP2002-1568, pp. 325-331; 7 pages
Published Online:
August 14, 2008
Citation
Simmons, K, Hibberd, S, Wang, Y, & Care, I. "Numerical Study of the Two-Phase Air/Oil Flow Within an Aero-Engine Bearing Chamber Model Using a Coupled Lagrangian Droplet Tracking Method." Proceedings of the ASME 2002 Pressure Vessels and Piping Conference. Computational Technologies for Fluid/Thermal/Structural/Chemical Systems With Industrial Applications, Volume 1. Vancouver, BC, Canada. August 5–9, 2002. pp. 325-331. ASME. https://doi.org/10.1115/PVP2002-1568
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