Numerical Study of the Two-Phase Air/Oil Flow Within an Aero-Engine Bearing Chamber Model Using a Coupled Lagrangian Droplet Tracking Method

2002 ◽  
Author(s):  
Kathy Simmons ◽  
Stephen Hibberd ◽  
Yi Wang ◽  
Ian Care
Keyword(s):  
Coupling Method ◽  
Oil Droplets ◽  
Two Phase ◽  
Droplet Motion ◽  
Tracking Method ◽  
Aero Engine ◽  
Oil Flow ◽  
Turbulent Airflow ◽  
Airflow Field ◽  
Engine Bearing

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.

A Numerical Model for Oil Film Flow in an Aero-Engine Bearing Chamber and Comparison With Experimental Data

2004 ◽  
Author(s):  
Mark Farrall ◽  
Kathy Simmons ◽  
Stephen Hibberd ◽  
Philippe Gorse
Keyword(s):  
Experimental Data ◽  
Boundary Conditions ◽  
Roller Bearing ◽  
Numerical Approach ◽  
Oil Droplets ◽  
Two Phase ◽  
Oil Film ◽  
Aero Engine ◽  
The Impact ◽  
Engine Bearing

The work presented forms part of an on-going investigation, focusing on modelling the motion of a wall oil film present in a bearing chamber and comparison with existing experimental data. The film is generated through the impingement of oil droplets shed from a roller bearing. Momentum resulting from the impact of oil droplets, interfacial shear from the airflow, and gravity cause the film to migrate around the chamber. Oil and air exit the chamber at scavenge and vent ports. A previously reported numerical approach to the simulation of steady-state two-phase flow in a bearing chamber, that includes in-house sub-models for droplet-film interaction and oil film motion, has been extended. This paper includes the addition of boundary conditions for the vent and scavenge together with a comparison to experimental results obtained from ITS, University of Karlsruhe. The solution is found to be sensitive to the choice of boundary conditions applied to the vent and scavenge.

Comparison of CFD and PIV Data for the Airflow in an Aero-Engine Bearing Chamber

2004 ◽  
Author(s):  
C. W. Lee ◽  
P. C. Palma ◽  
K. Simmons ◽  
S. J. Pickering
Keyword(s):  
Experimental Data ◽  
Fluid Transport ◽  
Cfd Simulation ◽  
Computational Modelling ◽  
Two Phase ◽  
Aero Engine ◽  
Flow Features ◽  
Airflow Field ◽  
Rsm Model ◽  
Engine Bearing

Investigations into the single-phase velocity field of a model aero-engine bearing chamber are presented. Adequately resolving the airflow field is important to subsequent computational modelling of two-phase fluid transport and heat transfer characteristics. A specially designed test rig, representing the features of a Rolls-Royce Trent series aero-engine bearing chamber, was constructed. Experimental data for the airflow field was obtained using particle image velocimetry (PIV). The results show a strong influence of shaft rotation and chamber geometry on the flow features within the bearing chamber. A computational fluid dynamics (CFD) simulation was carried out using the commercial CFD code FLUENT 6. Flow features were adequately modelled, showing the features of secondary velocities. Turbulence modelling using the differential Reynolds stress (RSM) model shows good agreement with the experimental data.

Further Computational Investigations Into Aero-Engine Bearing Chamber Off-Take Flows

2010 ◽  
Author(s):  
Adam Robinson ◽  
Carol Eastwick ◽  
Herve´ Morvan
Keyword(s):  
Experimental Work ◽  
Symmetry Plane ◽  
Two Phase ◽  
Pipe System ◽  
Aero Engine ◽  
Gravity Driven ◽  
Computational Fluid Dynamics Cfd ◽  
Modelling Assumptions ◽  
Static Head ◽  
Engine Bearing

Within an aero-engine bearing chamber oil is provided to components to lubricate and cool. This oil must be efficiently removed (scavenged) from the chamber to ensure it does not overheat and degrade. Bearing chambers typically contain a sump section with an exit pipe leading to a scavenge pump. In this paper a simplified geometry of a sump section, here simply made of a radial off-take port on a walled inclined plane, is analysed computationally. This paper follows on work presented within GT2008-50634. In the previous paper it was shown that simple gravity draining from a static head of liquid cold be modelled accurately, for what was akin to a deep sump situation fond in integrated gear boxes for example. The work within this paper will show that the draining of flow perpendicular to a moving film can be modelled. This situation is similar to the arrangements found in transmission bearing chambers. The case modelled is of a walled gravity driven film running down a plane with a circular off-take port, this replicates experimental work similar to that reported in GT2008-50632. The commercial computational fluid dynamics (CFD) code, Fluent 6 [1] has been employed for modelling, sing the Volume of Fluid (VOF) approach of Hirt and Nichols [2, 3] to capture the physics of both the film motion and the two phase flow in the scavenge pipe system. Surface tension [4] and a sharpening algorithm [5] are used to complement the representation of the free surface and associated effects. This initial CFD investigation is supported and validated with experimental work, which is only depicted briefly here as it is mainly sued to support the CFD methodology. The case has been modelled in full as well as with the use of a symmetry plane running down the centre of the plane parallel to the channel walls. This paper includes details of the meshing methodology, the boundary conditions sued, which will be shown to be of critical importance to accurate modelling, and the modelling assumptions. Finally, insight into the flow patterns observed for the cases modelled are summarised. The paper further reinforces that CFD is a promising approach to analysing bearing chamber scavenge flows although it can still be relatively costly.

scholarly journals Influences of the Geometry of the Scavenge Pipe on the Air–Oil Two-Phase Flow and Heat Transfer in an Aero-Engine Bearing Chamber

ACS Omega ◽  
2019 ◽  
Vol 4 (12) ◽  
pp. 15226-15233 ◽  
Author(s):  
Peng Lu ◽  
Lulu Fang ◽  
Xiangyang Wang ◽  
Qihang Ye ◽  
Jingzhou Zhang
Keyword(s):  
Heat Transfer ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Flow And Heat Transfer ◽  
Aero Engine ◽  
Engine Bearing

Film Flow Characteristics of Droplet Cooling in a Simplified Bearing Chamber

2013 ◽  
Author(s):  
E. D. Kay ◽  
H. Power ◽  
S. Hibberd
Keyword(s):  
Gas Turbines ◽  
Flow Characteristics ◽  
Temperature History ◽  
Design Parameters ◽  
Flow Conditions ◽  
Internal Surfaces ◽  
Aero Engine ◽  
Oil Flow ◽  
Oil Films ◽  
Engine Bearing

Droplet-cooled oil films develop on the internal surfaces of an aero-engine bearing chamber and are a primary mechanism in removing heat from the chamber as oil is continuously collected and externally cooled and recycled. Predicting the internal oil temperature and oil temperature history is an important thermal problem which becomes more apparent with potential increases in operating temperatures of gas turbines. Studying interacting oil flow and thermal processes within a simplified bearing chamber geometry provides useful information on the trends and characteristics which can arise under different applied flow conditions (e.g. mass flow rate of oil through the system) and insight to the effect chamber design parameters may have on oil degradation and cooling of chamber walls. Thin oil films develop on the walls of a bearing chamber as oil is injected or shed from bearings and impinges on the walls under a strong airflow set in motion by rotating components. Typically the film is also subject to a heat flux from the hot chamber walls and the droplets provide an important cooling effect through “heat-to-oil” mechanisms. We present a mathematical model for the depth-averaged flow and associated heat transfer by thin oil films on the walls of a simplified aero-engine bearing chamber. Cases corresponding to generic flow conditions relevant to an aero-engine bearing chamber are presented. Characteristics of the film and the efficacy of the flow regime to transfer heat from the chamber is explored through calculating residence times and time histories of oil particles as they make a transit of the internal system.

The study of droplet deformation and droplet volume fraction in an aero-engine bearing chamber

2018 ◽  
Vol 233 (6) ◽  
pp. 2264-2277
Author(s):  
Long Fang ◽  
Guoding Chen
Keyword(s):  
Volume Fraction ◽  
Theoretical Calculations ◽  
Research Work ◽  
Droplet Volume ◽  
Droplet Deformation ◽  
Two Phase ◽  
Aero Engine ◽  
Model Equations ◽  
Breakup Model ◽  
Engine Bearing

Inside an aero-engine bearing chamber, the shape, velocity, and temperature of each droplet shed from roller elements keep changing under the actions of the rotating airflow. Research on droplet deformation, droplet motion, and droplet volume fraction is fundamental to the understanding of the complex two-phase flow in an aero-engine bearing chamber. In this paper, the modified Taylor analogy breakup model, equations of temperature and motion are established to obtain the size, temperature, and velocity of a deformed droplet. Subsequently, a method is presented to solve for the droplet volume fraction in a bearing chamber based on the size and motion parameters of deformed droplets. In the end, a simplified bearing chamber experimental setup has been constructed. Comparisons between the experimental results and theoretical calculations show a good match based upon the research analogy used. The research work in this paper can provide theoretical foundations for the analyses of heat exchange and lubrication in bearing chambers. This also has great significance in realizing the rigorous design required for the lubrication system of an aero-engine.

Two-Phase Flow Pressure Drop in Corrugated Tubes Used in an Aero-engine Oil System

2015 ◽  
Vol 138 (6) ◽  
Author(s):  
Michael Flouros ◽  
Andreas Kanarachos ◽  
Kyros Yakinthos ◽  
Christina Salpingidou ◽  
Francois Cottier
Keyword(s):  
Pressure Drop ◽  
Two Phase Flow ◽  
Operating Conditions ◽  
Engine Oil ◽  
Phase Flow ◽  
Test Results ◽  
Two Phase ◽  
Aero Engine ◽  
Flow Pressure ◽  
Engine Bearing

In modern aero-engines, the lubrication system holds a key role due to the demand for high reliability standards. An aero-engine bearing chamber contains components like bearings and gears. Oil is used for lubrication and for heat removal. In order to retain the oil in a bearing chamber, pressurized seals are used. These are pressurized using air from the compressor. In order to avoid overpressurization of the bearing chamber, air/oil passages are provided in the bearing chamber. At the top, a vent pipe discharges most of the sealing air and at the bottom, a scavenge pipe is used for discharging the oil by means of a pump (scavenge pump). The scavenge pipe is setup in most cases by tubes of circular or noncircular cross sections. When the scavenge pipe has to be routed in a way that sharp bends or elbows are unavoidable, flexible (corrugated) pipes can be used. Because of the corrugation, considerable flow resistance with high-pressure drop can result. This may cause overpressurization of the bearing compartment with oil loss into the turbomachinery with possibility of ignition, coking (carbon formation), or contamination of the aircraft’s air conditioning system. It is therefore important for the designer to be capable to predict the system’s pressure balance behavior. A real engine bearing chamber sealed by brush seals was used for generating different air/oil mixtures thus corresponding to different engine operating conditions. The mixtures were discharged through a scavenge pipe which was partly setup by corrugated tubes. Instead of a mechanical pump, an ejector was used for evacuating the bearing chamber. An extensive survey covering the existing technical literature on corrugated tube pressure drop was performed and is presented in this paper. The survey has covered both single-phase and multiphase flows. Existing methods were checked against the test results. The method which was most accurately predicting lean air test results from the rig was benchmarked and was used as the basis for extending into a two-phase flow pressure drop correlation by applying two-phase flow multiplier techniques similar to Lockhart and Martinelli. Comparisons of the new two-phase flow pressure drop correlation with an existing correlation by Shannak are presented for mixtures like air/oil, air/water, air/diesel, and air/kerosene. Finally, numerical analysis results using ansys cfx version 15 are presented.

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

2014 ◽  
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.

Theoretical and experimental studies on the motion and thermal states of oil droplet in a bearing chamber

2016 ◽  
Vol 230 (14) ◽  
pp. 2596-2614 ◽  
Author(s):  
Hengchao Sun ◽  
Guoding Chen ◽  
Yonghong Zhang ◽  
Li’na Wang
Keyword(s):  
Operating Conditions ◽  
Similarity Criteria ◽  
Two Phase ◽  
Droplet Motion ◽  
Oil Droplet ◽  
Flow And Heat Transfer ◽  
Droplet Trajectory ◽  
The Difference ◽  
Thermal States ◽  
Engine Bearing

Study on the motion and thermal states of oil droplet is an important part of research on the oil/air two-phase flow and heat transfer in an aero engine bearing chamber. In this paper, dimensional analysis is applied to the airflow analysis of bearing chamber. That makes the analysis model suitable for a wide range of geometric and operating conditions. Moreover, the temperature solution is added to the oil droplet motion analysis. That could promote the calculation accuracy of the droplet trajectory, velocity, and temperature. Firstly, the similarity criteria of the airflow in a bearing chamber are determined based on the dimensional analysis. The airflow distribution general formulas are proposed based on the numerical results of airflow velocity and temperature. The general formulas include 14 similarity criteria and are suitable for various geometric and operating conditions. The reliability of the general formulas is verified by some available experimental results. Secondly, the difference equations of the oil droplet velocity and temperature are listed by the difference method. The velocity and temperature of the droplet are obtained using a step-by-step method. The influence of droplet diameter, shaft rotational speed, air flow rate, and temperature on the oil droplet trajectory, velocity, and temperature are discussed. Thirdly, a test facility is built in order to investigate into the oil droplet motion and thermal states in a bearing chamber. The trajectory and velocity of the oil droplet are measured by the high-speed photography. Lastly, the proposed theoretical method about the oil droplet motion and thermal states is verified by above measurement results. The work in this paper may have a certain significance for perfecting the research system and improving the research level on the oil/air two-phase flow and heat transfer in an aero engine bearing chamber.

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