scholarly journals Towards Investigation of External Oil Flow From a Journal Bearing in an Epicyclic Gearbox

2017 ◽  
Author(s):  
Martin Berthold ◽  
Hervé Morvan ◽  
Colin Young ◽  
Richard Jefferson-Loveday
Keyword(s):  
Flow Field ◽  
Journal Bearing ◽  
Numerical Models ◽  
Flow Behavior ◽  
Phase Interface ◽  
Journal Bearings ◽  
Field Behavior ◽  
Oil Flow ◽  
Inlet Conditions ◽  
Near Wall

High loads and bearing life requirements make journal bearings the preferred choice for use in high power, epicyclic gearboxes in jet engines. In contrast to conventional, non-orbiting journal bearings in epicyclic star gearboxes, the kinematic conditions in epicyclic planetary arrangements are much more complex. With the planet gears rotating about their own axis and orbiting around the sun gear, centrifugal forces generated by both motions interact with each other and affect the external flow behavior of the oil exiting the journal bearing. This paper presents a literature and state-of-the-art knowledge review to identify existing work performed on cases similar to external journal bearing oil flow. In order to numerically investigate external journal bearing oil flow, an approach to decompose an actual journal bearing into simplified models is proposed. Later, these can be extended in a step-wise manner to allow key underlying physical phenomena to be identified. Preliminary modeling considerations will also be presented. This includes assessing different geometrical inlet conditions with the aim of minimizing computational requirements and different numerical models for near-wall treatment. The correct choice of near-wall treatment models is particularly crucial as it determines the bearing’s internal and external thermal behavior and properties. The findings and conclusions are used to create a three dimensional (3D), two-component computational fluid dynamic (CFD) sector model with rotationally periodic boundaries of the most simplistic approximation of an actual journal bearing: a non-orbiting representation, rotating about its own axis, with a circumferentially constant, i.e. concentric, lubricating gap. The inlet boundary conditions for simulating the external oil flow are generated by partly simulating the internal oil flow within the lubricating gap. In order to track the phase interface between the oil and the air surrounding the bearing, the Volume of Fluid (VoF) method is used. The quality of the CFD simulations of the domain of interest is not only dependent on the accuracy of the inlet conditions, but is also dependent on the computational mesh type, cell count, cell shape and numerical methods used. External journal bearing oil flow was simulated with a number of different mesh densities and the effect on the flow field behavior will be discussed. Two different operating temperatures, representing low and high viscosity oil, were used and their effect on the flow field behavior will also be assessed. In order to achieve the future objective of creating a design tool for routine use, key areas will be identified in which further progress is required. This includes the need to progressively increase the model fidelity to eventually simulate an orbiting journal bearing in planetary configuration with an eccentric, i.e. convergent-divergent, lubricating gap.

scholarly journals Multiphase CFD Modeling of External Oil Flow From a Journal Bearing

2018 ◽  
Author(s):  
Martin Berthold ◽  
Hervé Morvan ◽  
Richard Jefferson-Loveday ◽  
Benjamin C. Rothwell ◽  
Colin Young
Keyword(s):  
Boundary Conditions ◽  
Journal Bearing ◽  
Flow Behavior ◽  
Phase Interface ◽  
Numerical Schemes ◽  
Ansys Fluent ◽  
Oil Film ◽  
Reconstruction Scheme ◽  
Geometric Reconstruction ◽  
Oil Flow

High loads and bearing life requirements make journal bearings a potential choice for use in high power, epicyclic gearboxes in jet engines. Particularly in a planetary configuration the kinematic conditions are complex. With the planet gears rotating about their own axis and orbiting around the sun gear, centrifugal forces generated by both motions interact with each other and affect the external flow behavior of the oil exiting the journal bearing. Computational Fluid Dynamics (CFD) simulations using the Volume of Fluid (VoF) method are carried out in ANSYS Fluent [1] to numerically model the two-phase flow behavior of the oil exiting the bearing and merging into the air surrounding the bearing. This paper presents an investigation of two numerical schemes that are available in ANSYS Fluent to track or capture the air-oil phase interface: the geometric reconstruction scheme and the compressive scheme. Both numerical schemes are used to model the oil outflow behavior in the most simplistic approximation of a journal bearing: a representation, rotating about its own axis, with a circumferentially constant, i.e. concentric, lubricating gap. Based on these simplifications, a three dimensional (3D) CFD sector model with rotationally periodic boundaries is considered. A comparison of the geometric reconstruction scheme and the compressive scheme is presented with regards to the accuracy of the phase interface reconstruction and the time required to reach steady state flow field conditions. The CFD predictions are validated against existing literature data with respect to the flow regime, the direction of the predicted oil flow path and the oil film thickness. Based on the findings and considerations of industrial requirements, a recommendation is made for the most suitable scheme to be used. With a robust and partially validated CFD model in place, the model fidelity can be enhanced to include journal bearing eccentricity. Due to the convergent-divergent gap and the resultant pressure field within the lubricating oil film, the outflow behavior can be expected to be very different compared to that of a concentric journal bearing. Naturally, the inlet boundary conditions for the oil emerging from the journal bearing into the external environment must be consistent with the outlet conditions from the bearing. The second part of this paper therefore focuses on providing a method to generate appropriate inlet boundary conditions for external oil flow from an eccentric journal bearing.

Multiphase Computational Fluid Dynamics Modeling of External Oil Flow From a Journal Bearing

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Martin Berthold ◽  
Hervé Morvan ◽  
Richard Jefferson-Loveday ◽  
Colin Young ◽  
Benjamin C. Rothwell ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Boundary Conditions ◽  
Journal Bearing ◽  
Flow Behavior ◽  
Phase Interface ◽  
Ansys Fluent ◽  
Reconstruction Scheme ◽  
Geometric Reconstruction ◽  
Oil Flow

High loads and bearing life requirements make journal bearings a potential choice for use in high power, epicyclic gearboxes in jet engines. Particularly, in a planetary configuration, the kinematic conditions are complex. With the planet gears rotating about their own axes and orbiting around the sun gear, centrifugal forces generated by both motions interact with each other and affect the external flow behavior of the oil exiting the journal bearing. Computational fluid dynamics (CFD) simulations using the volume of fluid (VoF) method are carried out in ANSYS fluent (ANSYS, 2013, “ANSYS Fluent User's Guide,” ANSYS Inc., Canonsburg, PA) to numerically model the two-phase flow behavior of the oil exiting the bearing and merging into the air surrounding the bearing. This paper presents an investigation of two numerical schemes that are available in ansysfluent to track or capture the air–oil phase interface: the geometric reconstruction scheme and the compressive scheme. Both numerical schemes are used to model the oil outflow behavior in the most simplistic approximation of a journal bearing: a representation, rotating about its own axis, with a circumferentially constant, i.e., concentric, lubricating gap. Based on these simplifications, a three-dimensional (3D) CFD sector model with rotationally periodic boundaries is considered. A comparison of the geometric reconstruction scheme and the compressive scheme is presented with regard to the accuracy of the phase interface reconstruction and the time required to reach steady-state flow-field conditions. The CFD predictions are validated against existing literature data with respect to the flow regime, the direction of the predicted oil flow path, and the oil film thickness. Based on the findings and considerations of industrial requirements, a recommendation is made for the most suitable scheme to be used. With a robust and partially validated CFD model in place, the model fidelity can be enhanced to include journal bearing eccentricity. Due to the convergent-divergent gap and the resultant pressure field within the lubricating oil film, the outflow behavior can be expected to be very different compared to that of a concentric journal bearing. Naturally, the inlet boundary conditions for the oil emerging from the journal bearing into the external environment must be consistent with the outlet conditions from the bearing. The second part of this paper therefore focuses on providing a method to generate appropriate inlet boundary conditions for external oil flow from an eccentric journal bearing.

Stability of Jeffcott Rotor Operating in Tilting 3-Pad Journal Bearings with Turbulent Oil Film

2009 ◽  
Vol 147-149 ◽  
pp. 450-455
Author(s):  
Stanislaw Strzelecki ◽  
Sobhy M. Ghoneam
Keyword(s):  
Theoretical Investigation ◽  
Dynamic Characteristics ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Oil Film ◽  
Temperature Distributions ◽  
Jeffcott Rotor ◽  
Oil Flow ◽  
The Stability ◽  
Oil Film Pressure

This paper introduces the results of theoretical investigation on the dynamic characteristics of tilting 3-pad journal bearing that operates with turbulent oil film. The Reynolds, energy, viscosity and geometry equations determine the oil film pressure, temperature distributions, and oil film resultant force that are the grounds for the dynamic characteristics of bearing. These equations were solved simultaneously on the assumption of adiabatic laminar or adiabatic turbulent oil flow in the bearing gap. The stability and system damping of Jeffcott rotor operating in tilting 3-pad journal bearing was determined.

scholarly journals Numerical Modeling of Flow Field in Morning Glory Spillways and Determining Rating Curve at Different Flow Rates

2016 ◽  
Vol 2 (9) ◽  
pp. 448-457 ◽  
Author(s):  
Mohammad Reza Enjilzadeh ◽  
Ebrahim Nohani
Keyword(s):  
Numerical Model ◽  
Flow Field ◽  
Numerical Modelling ◽  
Relative Error ◽  
Numerical Models ◽  
Discharge Rate ◽  
Morning Glory ◽  
Physical Models ◽  
Rating Curve ◽  
Inlet Conditions

Morning glory spillways with drop inlets are normally employed in dams built on narrow valleys or placed on steep slopes. In Iran, morning glory spillways have been commonly used in large Dam projects such as Sefidrood dam, Alborz dam, and Haraz dam. Physical models should be built to accurately determine hydraulic parameters of the flow and flow field in spillways. Establishment of a physical model involves extravagant costs and conditions that cannot be justified in some cases. Therefore, suitable numerical models can be proposed for such circumstances. Using FLOW3D numerical models, 3-dimensional numerical modelling of the flow was calibrated and validated by experimental information associated with morning glory spillway of Alborz dam and accuracy of numerical modelling was determined by relative error of numerical model. So it was attempted to determine flow pattern and control conditions of morning glory spillways in different modes using boundary conditions, inlet conditions and grid spacing of flow field and project rating curve of morning glory spillways. According to the results of numerical model, relative error of numerical modelling equals 6.4% for calculating discharge rate of the spillways. Numerical modelling error is 7.6% for determining depth parameter of the flow in spillway crest in comparison with experimental results.

Experimental Verification of a New Model for Transition Flow of Thin Films in Long Journal Bearings

2010 ◽  
Author(s):  
Dingfeng Deng ◽  
Minel J. Braun
Keyword(s):  
Experimental Verification ◽  
Journal Bearing ◽  
Flow Behavior ◽  
Journal Bearings ◽  
Turbulent Regime ◽  
Transition Flow ◽  
New Model ◽  
Taylor Vortices ◽  
The Difference ◽  
Good Agreement

A new model for predicting the flow behavior in long journal bearing films in the transition regime (Taylor and wavy vortex regimes) was previously proposed by the authors. This paper presents the experimental verification. A comparison between the experimental and numerical results of the Torque–Speed graphs is presented with good agreement between the numerical and experimental data for the Couette, Taylor and pre-wavy regimes. In the wavy and turbulent regime, the magnitude of the numerically obtained data is larger than the corresponding measured torques, but the difference is confined to below 14%. A comparison between experimental and numerical flow patterns is also presented. The results match well in general, except that experimentally, a pre-wavy regime was identified. The latter is characterized by the disappearance of the Taylor vortices, while numerically the Taylor vortices are only distorted and the wavy vortices are formed in this regime.

scholarly journals Toward Investigation of External Oil Flow From a Journal Bearing in an Epicyclic Gearbox

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Martin Berthold ◽  
Hervé Morvan ◽  
Colin Young ◽  
Richard Jefferson-Loveday
Keyword(s):  
Journal Bearing ◽  
Phase Interface ◽  
Three Dimensional ◽  
High Viscosity ◽  
Design Tool ◽  
Jet Engines ◽  
Sector Model ◽  
Bearing Life ◽  
Oil Flow ◽  
High Viscosity Oil

High loads and bearing life requirements make journal bearings the preferred choice for use in high-power, planetary gearboxes in jet engines. With the planet gears rotating about their own axis and orbiting around the sun gear, centrifugal forces generated by both motions interact with each other and create complex kinematic conditions. This paper presents a literature and state-of-the-art knowledge review to identify existing work performed on cases similar to external journal bearing oil flow. In order to numerically investigate external journal bearing oil flow, an approach to decompose an actual journal bearing into simplified models is proposed. Preliminary modeling considerations are discussed. The findings and conclusions are used to create a three-dimensional (3D), two-component computational fluid dynamics (CFD) sector model with rotationally periodic boundaries of the most simplistic approximation of an actual journal bearing: a nonorbiting representation, rotating about its own axis, with a circumferentially constant, i.e., concentric, lubricating gap. In order to track the phase interface between the oil and the air, the volume of fluid (VoF) method is used. External journal bearing oil flow is simulated with a number of different mesh densities. Two different operating temperatures, representing low and high viscosity oil, are used to assess the effect on the external flow field behavior. In order to achieve the future objective of creating a design tool for routine use, key areas are identified in which further progress is required.

Validation of Turbulence Models for the Superlaminar Flows in Journal Bearings

2017 ◽  
Author(s):  
Aoshuang Ding ◽  
Xiaodong Ren
Keyword(s):  
Buffer Layer ◽  
Turbulence Models ◽  
Journal Bearings ◽  
Wall Turbulence ◽  
Fully Developed Turbulence ◽  
Developed Turbulence ◽  
Sst Model ◽  
Oil Flow ◽  
Near Wall Turbulence ◽  
Near Wall

With the development of high speed rotating machinery, the flow regime in bearings changes from laminar to superlaminar, that is, the flow is between laminar and fully developed turbulent. The superlaminar oil flow in an oil–lubricated tilting–pad journal bearing is analyzed in this study. A three–dimensional model for the oil domain is established and the CFD results obtained using laminar and seventeen turbulence models are compared with the experimental results obtained by S.Taniguchi. The seventeen turbulence models are divided into three groups, namely, classical fully developed turbulence models, transition turbulence models, and turbulence models with low–Re correction. The laminar and classical turbulence models cannot simulate the superlaminar flow correctly; accordingly, corrections should be applied to classical fully developed turbulence models for superlaminar flows to consider the turbulent effect properly. However, not all corrections are suitable. Among all the compared turbulence models, the SST model with low–Re correction performs the best. Furthermore, this model can capture the turbulent effect in superlaminar oil flow, as indicated in the analysis of turbulent viscosity ratio. A comparison of the velocity profiles shows that the mechanism of the superlaminar flow in journal bearings is near–wall turbulence. The buffer layer plays an important role in superlaminar flows. The SST model with low–Re correction can likewise capture the characteristics of the buffer layer and simulate the near–wall turbulence properly in superlaminar flows. Thus in superlaminar journal bearings, the low–Re correction is the most suitable correction for the SST turbulence model for simulating oil flows.

Paper 8: A Graphical Method for Predicting the Performance of Circumferentially Grooved Hydrodynamic Journal Bearings under Steady Loads

1965 ◽  
Vol 180 (11) ◽  
pp. 160-173
Author(s):  
F. A. Martin
Keyword(s):  
Iterative Process ◽  
Journal Bearing ◽  
Graphical Method ◽  
Design Method ◽  
Simultaneous Equations ◽  
Eccentricity Ratio ◽  
Normal Manner ◽  
Oil Flow ◽  
Bearing Design ◽  
Inlet Conditions

This paper illustrates a procedure of bearing design which avoids the iterative process of conventional methods of determining the eccentricity ratio in a journal bearing. The iterative process results from the need to satisfy three simultaneous equations; in the method described, the equations are graphically defined on two sheets. The transparent sheet defines the bearing data and eccentricity ratio and the opaque sheet defines the viscosity-temperature characteristics of the oil chosen. The transparent sheet is moved over the opaque sheet according to a fixed locus till a point representing the bearing data is coincident with the oil inlet conditions. The eccentricity ratio can be read directly and power loss and oil flow calculations may then be carried out in the normal manner. Experimental results obtained from tests with circumferentially grooved bearings have been used to test the generality of the design method and also to check the assumptions relating to operating viscosities in the bearing.

Oil Wave Journal Bearing Steady-State Data From a New Test Rig

2008 ◽  
Author(s):  
Florin Dimofte ◽  
Nicoleta M. Ene ◽  
Fred B. Oswald
Keyword(s):  
Steady State ◽  
Journal Bearing ◽  
Rotation Speed ◽  
Constant Load ◽  
Journal Bearings ◽  
Test Rig ◽  
State Data ◽  
Air Turbine ◽  
Oil Flow ◽  
Significant Attenuation

An oil lubricated wave bearing has been tested on a new rig for fluid film journal bearings at NASA Glenn Research Center in Cleveland, Ohio, USA. The tests are intended to evaluate the rig possibilities of running without misalignment. Data recorded under steady-state conditions included oil flow rate, input, output and oil supply temperatures, and shaft position. Two sets of data were collected: i) by varying the load to 9000 N at a constant shaft rotation speed of 8,000 RPM and ii) by varying the speed from 9,000 to 12,000 RPM at constant load of 6,700 N. The temperatures of the metal sleeves were also recorded. Vibration levels at four locations were displayed and recorded. These measurements indicated that damping from the wave bearings provides significant attenuation of the vibration generated by the air turbine that drives the rig.

Effects of Nonuniform Tip Clearance on Fan Performance and Flow Field

2015 ◽  
Author(s):  
Yingxiu Chen ◽  
Anping Hou ◽  
Mingming Zhang ◽  
Jianxiong Li ◽  
Simu Zhang
Keyword(s):  
Flow Field ◽  
Aerodynamic Force ◽  
Numerical Models ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Stall Margin ◽  
Fan Performance ◽  
Two Factors ◽  
Clearance Level

Nonuniform tip clearance, caused by the deformation of the casing (casing ovalization), exists in all fans to some extent. However, description of the flow behavior with this kind of nonuniform clearance is seldom given in the open literature. In this paper, both steady and unsteady calculations are performed to study the influence of the nonuniform clearance on fan performance and flow field. The investigation method is based on three dimensional RANS equations, carried out by the ANSYS CFX fluid solver. A new factor τ, which is in the range of 0 to 1, is defined to represent the nonuniformity of the tip clearance. A series of numerical models with different tip clearance nonuniformities τ are investigated. In addition, the original, uniform tip clearance is also performed serving as a reference. The results indicate that the fan performance is mainly affected by two factors: the clearance nonuniformity τ and the average clearance level. There is a clear decreasing trend of the fan performance with increasing nonuniformity and average tip clearance level. The maximum clearance can contribute to the reduction of stall margin. Furthermore, the effects of nonuniform clearance on tip leakage vortex and aerodynamic force are also discussed in detail. The deformation of the casing can affect the pressure fluctuation and thus increase the amplitude of the aerodynamic force.

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