Prediction of Film Thickness of an Aero-Engine Bearing Chamber Using Coupled VOF and Thin Film Model

Abstract In the present work, a coupled volume-of-fluid (VOF) model with Eulerian thin-film model (ETFM) approach is used to predict the film thickness in an aero-engine bearing chamber. Numerical studies are conducted for a wide range of shaft speeds with lubricant and air flow rates of 100 1/hr and 10 g/s respectively, at a scavenge ratio of 4 on a simplified bearing chamber test rig. Air-flow analysis inside the bearing chamber is also assessed. Primary and secondary airflow predictions are found to be in good agreement with the experimental results. The coupled ETFM+VOF approach is found to be sensitive enough to capture the qualitative trend of oil film formation and distribution over the chamber wall. Oil collection near the sump at a low shaft speed and a rotating oil film at a higher shaft speed are well captured.

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Modelling of Partially Wetting Liquid Film Using an Enhanced Thin Film Model for Aero-Engine Bearing Chamber Applications

Volume 2C: Turbomachinery ◽

10.1115/gt2020-15845 ◽

2020 ◽

Author(s):

K. Singh ◽

M. Sharabi ◽

R. Jefferson-Loveday ◽

S. Ambrose ◽

C. Eastwick ◽

...

Keyword(s):

Thin Film ◽

Contact Angle ◽

Film Thickness ◽

Liquid Film ◽

Flow Rate ◽

Operating Conditions ◽

Film Model ◽

Thin Film Model ◽

Wide Range ◽

Aero Engine

Abstract In the case of aero-engine, thin lubricating film servers dual purpose of lubrication and cooling. Prediction of dry patches or lubricant starved region in bearing or bearing chambers are required for safe operation of these components. In the present work thin liquid film flow is numerically investigated using the framework of the Eulerian thin film model (ETFM) for conditions which exhibit partial wetting phenomenon. This model includes a parameter that requires adjustment to account for the dynamic contact angle. Two different experimental data sets have been used for comparisons against simulations, which cover a wide range of operating conditions including varying the flow rate, inclination angle, contact angle, and liquid-gas surface tension coefficient. A new expression for the model parameter has been proposed and calibrated based on the simulated cases. This is employed to predict film thickness on a bearing chamber which is subjected to a complex multiphase flow. From this study, it is observed that the proposed approach shows good quantitative comparisons of the film thickness of flow down an inclined plate and for the representative bearing chamber. A comparison of model predictions with and without wetting and drying capabilities is also presented on the bearing chamber for shaft speed in the range of 2,500 RPM to 10,000 RPM and flow rate in the range of 0.5 liter per minute (LPM) to 2.5 LPM.

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Modeling of Partially Wetting Liquid Film Using an Enhanced Thin Film Model for Aero-Engine Bearing Chamber Applications

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4049663 ◽

2021 ◽

Vol 143 (4) ◽

Author(s):

Kuldeep Singh ◽

Medhat Sharabi ◽

Richard Jefferson-Loveday ◽

Stephen Ambrose ◽

Carol Eastwick ◽

...

Keyword(s):

Thin Film ◽

Contact Angle ◽

Film Thickness ◽

Liquid Film ◽

Thin Liquid Film ◽

Operating Conditions ◽

Film Model ◽

Thin Film Model ◽

Wide Range ◽

Aero Engine

Abstract In the case of aero-engine, thin lubricating film servers dual purpose of lubrication and cooling. Prediction of dry patches or lubricant starved region in bearing or bearing chambers are required for safe operation of these components. In this work, thin liquid film flow is numerically investigated using the framework of the Eulerian thin film model (ETFM) for conditions, which exhibit partial wetting phenomenon. This model includes a parameter that requires adjustment to account for the dynamic contact angle. Two different experimental data sets have been used for comparisons against simulations, which cover a wide range of operating conditions including varying the flowrate, inclination angle, contact angle, and liquid–gas surface tension coefficient. A new expression for the model parameter has been proposed and calibrated based on the simulated cases. This is employed to predict film thickness on a bearing chamber which is subjected to a complex multiphase flow. From this study, it is observed that the proposed approach shows good quantitative comparisons of the film thickness of flow down an inclined plate and for the representative bearing chamber. A comparison of model predictions with and without wetting and drying capabilities is also presented on the bearing chamber for shaft speed in the range of 2500 RPM to 10,000 RPM and flowrate in the range of 0.5 liter per minute (LPM) to 2.5 LPM.

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Assessment of an Enhanced Thin Film Model to Capture Wetting and Drying Behavior in an Aero-Engine Bearing Chamber

Volume 2C: Turbomachinery ◽

10.1115/gt2019-91323 ◽

2019 ◽

Author(s):

Kuldeep Singh ◽

Medhat Sharabi ◽

Stephen Ambrose ◽

Carol Eastwick ◽

Richard Jefferson-Loveday ◽

...

Keyword(s):

Thin Film ◽

Contact Angle ◽

Film Thickness ◽

Wetting And Drying ◽

Film Model ◽

Thin Film Model ◽

Aero Engine ◽

Thickness Prediction ◽

Drying Behavior ◽

Engine Bearing

Abstract In the present work, a wetting and drying model is coupled with Eulerian Thin-Film model (ETFM) to analyze the wetting and drying behavior inside the bearing chamber. In the enhanced model, an additional source term is included to account for the contact angle effect. These models were coupled with volume-of-fluid (VOF) such that the core region is resolved by VOF and region close to the chamber walls, where a thin film is expected is resolved by either ETFM or enhanced ETFM model. Numerical studies are conducted for a shaft speed of 5,000 rpm, lubricant and air flow rates of 100 1/hr and 10 g/s respectively, at a scavenging ratio of 4. In the case of enhanced ETFM model lubricant to surface contact angle was varied from 10° to 45°. The performance of enhanced ETFM model is evaluated to capture drying and wetting behavior on a flat plate and found to be satisfactory. Film thickness prediction of enhanced ETFM model is found to be comparable with the VOF predictions reported in the literature. The effect of contact angle on the spreading of oil and film thickness is found to be small for the investigated conditions on an aero-engine bearing chamber.

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Specifying and Benchmarking a Thin Film Model for Oil Systems Applications in ANSYS Fluent

Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Controls, Diagnostics and Instrumentation ◽

10.1115/gt2012-68984 ◽

2012 ◽

Cited By ~ 1

Author(s):

C. Wang ◽

H. P. Morvan ◽

S. Hibberd ◽

K. A. Cliffe ◽

A. Anderson ◽

...

Keyword(s):

Thin Film ◽

Film Flow ◽

Test Case ◽

Thin Film Flow ◽

Ansys Fluent ◽

Film Model ◽

Thin Film Model ◽

Software Product ◽

Aero Engine ◽

Engine Bearing

A thin film model developed for calculating the oil film flow in aero-engine bearing chamber is described. The performance of the model, which has been implemented in the commercial computational fluid dynamics software product: ANSYS Fluent, is benchmarked by comparing the computational results obtained from a Nottingham UTC in-house code and a development version of Fluent. Both codes are used to solve thin film flow in a test case configuration and based on the same finite area method. With identified constraints, the two implementations agree well.

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A Coupled 1D Film Hydrodynamics and Core Gas Flow Model for Air-Oil Flows in Aero-Engine Bearing Chambers

Volume 2B: Turbomachinery ◽

10.1115/gt2017-64693 ◽

2017 ◽

Author(s):

B. Kakimpa ◽

H. P. Morvan ◽

S. Hibberd

Keyword(s):

Shear Stress ◽

Operating Conditions ◽

Engine Oil ◽

Interface Shear ◽

Interface Shear Stress ◽

Oil Film ◽

Film Model ◽

Aero Engine ◽

Film Interface ◽

Engine Bearing

A robust 1D film hydrodynamic model has been sequentially coupled with a 1D core gas model and used to predict the instantaneous mean core gas speed, film interface shear stress and liquid film distribution within an idealised bearing chamber. This novel approach to aero-engine bearing chamber simulation provides a predictive tool that can be used for the fast and reliable exploration of a set of bearing chamber design and operating conditions characterised by the: chamber dimensions, air/oil fluid properties, shaft speed, sealing air flows, oil feed rates and sump scavenge ratios. A preliminary validation of the model against available bearing chamber flow measurements from literature shows good agreement. The model represents a significant step change in predictive capabilities for aero-engine oil system flows compared to previous semi-empirical models. The bearing chamber is idealised as a one-dimensional (2D) domain with a predominantly azimuthal flow in both the rotational oil film and core gas such that axial components may be ignored. A 1D system of depth-averaged film hydrodynamics equations is used to predict oil film thickness and mean speed distributions in the azimuthal direction under the influence of interface shear, gravity, pressure gradient and surface tension forces. The driving shear stress in the film model is obtained from the 1D core-gas model based on an azimuthal gas momentum conservation equation which is coupled to the film model through the interface shear stress and film interface velocity.

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Influences on the Oil Split Between the Offtakes of an Aero-Engine Bearing Chamber

Volume 4: Heat Transfer, Parts A and B ◽

10.1115/gt2012-69412 ◽

2012 ◽

Cited By ~ 4

Author(s):

Wolfram Kurz ◽

Klaus Dullenkopf ◽

Hans-Jörg Bauer

Keyword(s):

Film Thickness ◽

Test Rig ◽

Oil Film ◽

Aero Engine ◽

The Impact ◽

Engine Bearing

The aim of the presented work was to identify factors that influence the oil split between the two offtakes of a vented aero-engine bearing chamber. The impact of different vent and scavenge offtake designs was experimentally investigated with a test rig at the ITS. The generic bearing chamber was also equipped with ten film thickness sensors. The film measurements allowed a further evaluation of the mechanisms behind different oil splits. Two of the examined offtake features ensured a very constant oil split: a protruding vent and a covered ramp offtake. The latter also decreased the oil film thickness on the bearing chamber walls significantly. Furthermore, an influence of a non-uniform seal gap was detected which altered the oil split by several percent.

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An Approach for Predicting the Flow Regime in an Aero Engine Bearing Chamber

Volume 5C: Heat Transfer ◽

10.1115/gt2014-26756 ◽

2014 ◽

Cited By ~ 1

Author(s):

Wolfram Kurz ◽

Hans-Jörg Bauer

Keyword(s):

Flow Regime ◽

Air Flow ◽

Flow Regimes ◽

Chamber Pressure ◽

Test Rig ◽

Oil Viscosity ◽

Oil Film ◽

Aero Engine ◽

Oil Flow ◽

Engine Bearing

The paper discusses an approach to predict the two-phase flow regime in an aero engine bearing chamber. In general, one of two distinct flow regimes can occur in a bearing chamber. At lower shaft speeds, the oil flow is only partially affected by the air flow, which is driven by the rotating shaft. At higher shaft speeds, however, the rotating air flow forces the oil film at the chamber walls to rotate, too. Thus, the two flow regimes correspond to two very different oil film distributions inside a bearing chamber presumably with significant consequences for the internal wall heat transfer. In order to determine the driving parameters for the flow regimes and the change between them, experiments were carried out with a bearing chamber test rig. With this test rig all relevant operating parameters as well as the geometry of the bearing chamber could be varied independently. The analysis of the experimental data allowed defining a general parameter which takes into account the chamber pressure, shaft speed, oil viscosity and chamber length. The influence of the oil flow rate and the overall dimensions are assessed qualitatively.

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On the liquid lining in fluid-conveying curved tubes

Journal of Fluid Mechanics ◽

10.1017/jfm.2011.346 ◽

2011 ◽

Vol 705 ◽

pp. 213-233 ◽

Cited By ~ 8

Author(s):

Andrew L. Hazel ◽

Matthias Heil ◽

Sarah L. Waters ◽

James M. Oliver

Keyword(s):

Thin Film ◽

Surface Tension ◽

Film Thickness ◽

Secondary Flows ◽

Immiscible Fluid ◽

Straight Tube ◽

Core Flow ◽

Film Model ◽

Thin Film Model ◽

Axial Pressure Gradient

AbstractWe consider axially uniform, two-phase flow through a rigid curved tube in which a fluid (air) core is surrounded by a film of a second, immiscible fluid (water): a simplified model for flow in a conducting airway of the lung. Jensen (1997) showed that, in the absence of a core flow, surface tension drives the system towards a configuration in which the film thickness tends to zero on the inner wall of the bend. In the present work, we demonstrate that the presence of a core flow, driven by a steady axial pressure gradient, allows the existence of steady states in which the film thickness remains finite, a consequence of the fact that the tangential stresses at the interface, imposed by secondary flows in the core, can oppose the surface-tension-driven flow. For sufficiently strong surface tension, the steady configurations are symmetric about the plane containing the tube’s centreline, but as the surface tension decreases the symmetry is lost through a pitchfork bifurcation, which is closely followed by a limit point on the symmetric solution branch. This solution structure is found both in simulations of the Navier–Stokes equations and a thin-film model appropriate for weakly curved tubes. Analysis of the thin-film model reveals that the bifurcation structure arises from a perturbation of the translational degeneracy of the interface location in a straight tube.

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Thin Film Modelling for Aero-Engine Bearing Chambers

Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Wind Turbine Technology ◽

10.1115/gt2011-46259 ◽

2011 ◽

Cited By ~ 1

Author(s):

C. Wang ◽

H. P. Morvan ◽

S. Hibberd ◽

K. A. Cliffe

Keyword(s):

Thin Film ◽

Film Flow ◽

Momentum Equation ◽

Thin Film Flow ◽

Simple Formulation ◽

Physical Mechanisms ◽

Thin Film Model ◽

Aero Engine ◽

Flow Features ◽

Engine Bearing

This paper presents a dynamic mathematical model describing the thin film flow in aero-engine bearing chamber. By analyzing the depth averaged continuity equation and momentum equation term by term, the comprehensive physical mechanisms driving thin film flow are revealed. The terms that require extra modeling work are then identified. As a useful first approach, a thin film model based on presumed quadratic velocity profile is adopted. A preliminary study shows that this model can include the main film flow features in aero-engine bearing chamber, whilst maintain simple formulation and work efficiently. Finally, a converging computational strategy is obtained towards the numerical simulation of engine bearing chamber.

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