Oil Film Dynamics in Aero Engine Bearing Chambers
Amir A. Hashmi
Cite this publication as
Amir A. Hashmi, Oil Film Dynamics in Aero Engine Bearing Chambers (2012), Logos Verlag, Berlin, ISBN: 9783832593650
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Descripción / Abstract
Aero engine bearing chambers are complex machine elements inside the engines, supporting up to three concentric shafts on bearings. For safety reasons, the aero engines always employ rolling-element type bearings and therefore require a sufficient oil supply for lubrication in order to guarantee a reliable operation. As a consequence, a complex two-phase flow consisting of oil and sealing air governs the bearing chambers. A highly dynamic oil film, flowing along the chamber walls, plays a vital role to fulfill the tasks of cooling, lubricating and cleaning the bearing chambers. The design and optimization process of the bearing chambers requires a detailed understanding in order to accurately simulate the film behaviour inside the bearing chambers. Based on the earlier experimental investigations, it is known that near the scavenge off-take a relatively thick film exists. The numerical model to simulate these films must therefore take into account the elliptical behaviour of such films. Among the different models, the Volume Of Fluid (VOF) Model offers the best compromise between accuracy and efforts. However, preliminary attempts to model a fully developed and turbulent test case from literature revealed an unphysical pressure drop and velocity profile in the gas phase above the film flow. An inadequate turbulence modelling near the gas-liquid interface was identified as the problem source. The 2-Equation turbulence models (k- epsilon & k- omega) were extended to achieve a substantial improvement.
Índice
- BEGINN
- 1 Introduction - Bearing Chambers in Aero Engines
- 2 Oil Film Dynamics - State of the Art
- 2.1 Experimental Investigations
- 2.2 Numerical Investigations
- 3 Problem Definition and Concretization of Objectives
- 3.1 Problem Definition
- 3.2 Scope of the Thesis
- 3.3 Concretization of Objectives
- 4 Experimental Investigations of Thick Film Flows
- 4.1 Stratified Flow Test Rig
- 4.2 Experimental Results and Discussion
- 4.3 Significance of the Generic Results in a Bearing Chamber Environment
- 4.4 Characterization of Bearing Chamber Typical Oil Film Flows
- 5 Modelling of Shear Driven Thick Film Flows
- 5.1 Multiphase Modelling Techniques
- 5.2 Multiphase Turbulence Modelling
- 5.3 Application of the VOF Model to Thick Film Flows
- 5.4 Improved VOF Model
- 6 Simulation Results and Discussion
- 6.1 Test Case #1 - High Viscosity Liquid
- 6.2 Test Case #2 - ITS Stratified Flow Test Rig
- 7 Application Oriented Test Case - ITS HSBC Test Rig
- 7.1 Experimental Setup
- 7.2 Simulation Setup
- 7.3 Validation and Analysis
- 8 Summary and Outlook