Two-phase air/oil flow in aero engine bearing chambers: characterization of oil film flows

1997 ◽  
Vol 23 (7) ◽  
pp. 79
Keyword(s):  
Two Phase ◽  
Oil Film ◽  
Aero Engine ◽  
Oil Flow ◽  
Film Flows ◽  
Engine Bearing

Two-Phase Air/Oil Flow in Aero Engine Bearing Chambers: Characterization of Oil Film Flows

1996 ◽  
Vol 118 (3) ◽  
pp. 578-583 ◽  
Author(s):  
A. Glahn ◽  
S. Wittig
Keyword(s):  
High Speed ◽  
Force Balance ◽  
Two Phase ◽  
Oil Film ◽  
Theoretical Approaches ◽  
Geometric Conditions ◽  
Oil Flow ◽  
Secondary Air ◽  
Film Flows

For the design of secondary air and lubrication oil systems, a sufficient knowledge of two-phase flow and heat transfer phenomena under bearing chamber flow conditions is required. The characterization of oil film flows at the bearing chamber walls is one of the major tasks for a better understanding of these processes and, therefore, a necessity for improvements of the efficiency of aero engines. The present paper gives a contribution to this subject. Utilizing a fiber-optic LDV setup, measurements of oil film velocity profiles have been performed in our high-speed bearing chamber rig simulating real engine conditions. All data have been compared with different theoretical approaches, which have been derived from a force balance at a liquid film element, including geometric conditions and temperature dependent fluid properties, and by approaches for the eddy viscosity available in the literature.

Two-Phase Air/Oil Flow in Aero Engine Bearing Chambers: Characterization of Oil Film Flows

1995 ◽  
Author(s):  
A. Glahn ◽  
S. Wittig
Keyword(s):  
High Speed ◽  
Force Balance ◽  
Two Phase ◽  
Oil Film ◽  
Theoretical Approaches ◽  
Oil Flow ◽  
Secondary Air ◽  
Aero Engines ◽  
Film Flows

For the design of secondary air and lubrication oil systems a sufficient knowledge on two-phase flow and heat transfer phenomena under bearing chamber flow conditions is required. The characterization of oil film flows at the bearing chamber walls is one of the major tasks for a better understanding of these processes and, therefore, a necessity for improvements of the efficiency of aero engines. The present paper gives a contribution to this subject. Utilizing a fibre-optic LDV-setup, measurements of oil film velocity profiles have been performed in our high speed bearing chamber rig simulating real engine conditions. All data have been compared with different theoretical approaches which have been derived from a force balance at a liquid film element, including geometrical conditions and temperature dependent fluid properties, and by approaches for the eddy viscosity available in the literature.

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.

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.

scholarly journals Two-Phase Air/Oil Flow in Aero-Engine Bearing Chambers – Assessment of an Analytical Prediction Method for the Internal Wall Heat Transfer

1999 ◽  
Vol 5 (3) ◽  
pp. 155-165 ◽  
Author(s):  
A. Glahn ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Prediction Method ◽  
Analytical Prediction ◽  
Two Phase ◽  
Gravity Forces ◽  
Lubrication Oil ◽  
Oil Flow ◽  
Aero Engines ◽  
Film Flows ◽  
Engine Bearing

The present paper gives a theoretical outline on liquid film flows driven by superimposed effects of interfacial shear and gravity forces and discusses related heat transfer processes which are relevant for lubrication oil systems of aero engines. It is shown that a simple analytical approach is able to predict measured heat transfer data fairly well. Therefore, it offers scope for improvements within the analysis of bearing chamber heat transfer characteristics as well as for appropriate studies with respect to other components of the lubrication oil system such as vent pipeline elements.

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.

Study of Oil Film Heat Transfer in Gas Turbine Engine Bearing Chamber

2021 ◽  
Author(s):  
Illia Petukhov ◽  
Taras Mykhailenko ◽  
Oleksii Lysytsia ◽  
Artem Kovalov
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Gas Turbine ◽  
Gas Turbine Engine ◽  
Flow Core ◽  
Two Phase ◽  
Turbine Engine ◽  
Oil Film ◽  
Phase Medium ◽  
Engine Bearing

Abstract A clear understanding of the heat transfer processes in a gas turbine engine bearing chamber at the design stage makes it possible to properly design the lubrication and sealing systems and ensure the future bearing safe operation. The heat transfer coefficient (HTC) calculated based on the classical Newton-Richman equation is widely used to represent the heat transfer data and useful for the thermal resistance analysis. However, this approach is only formally applicable in the case of a two-phase medium. While there is a need to model a two-phase medium, setting the flow core temperature correctly in the Newton-Richman equation is an issue that is analyzed in this study. The heat from the flow core is transferred to the boundary of the oil film on the bearing chamber walls by an adjacent air and precipitating droplets. The analysis showed that droplet deposition plays a decisive role in this process and significantly intensifies the heat transfer. The main contribution to the thermal resistance of internal heat transfer is provided by the oil film. In this regard, the study considers the issues of the bearing chamber workflow modeling allowing to determine the hydrodynamic parameters of the oil film taking into account air and oil flow rates and shaft revolutions. The study also considers a possibility to apply the thermohydraulic analogy methods for the oil film thermal resistance determination. The study presents practical recommendations for process modeling in the bearing chamber.

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.

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