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Research Papers: Gas Turbines: Structures and Dynamics

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

[+] Author and Article Information
Martin Berthold

Gas Turbine and Transmissions
Research Centre (G2TRC),
University of Nottingham,
Energy Technology Building,
Nottingham NG7 2RD, UK
e-mail: eaxmb3@nottingham.ac.uk

Hervé Morvan

Professor
Gas Turbine and Transmissions
Research Centre (G2TRC),
University of Nottingham,
Coates Building,
Nottingham NG7 2RD, UK
e-mail: herve.morvan@nottingham.ac.uk

Colin Young

Rolls-Royce plc,
P.O. Box 31,
Derby DE24 8BJ, UK
e-mail: colin.young@rolls-royce.com

Richard Jefferson-Loveday

Gas Turbine and Transmissions
Research Centre (G2TRC),
University of Nottingham,
Coates Building,
Nottingham NG7 2RD, UK
e-mail: richard.jefferson-loveday@nottingham.ac.uk

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 28, 2017; final manuscript received August 24, 2017; published online January 17, 2018. Editor: David Wisler.

J. Eng. Gas Turbines Power 140(6), 062501 (Jan 17, 2018) (9 pages) Paper No: GTP-17-1410; doi: 10.1115/1.4038284 History: Received July 28, 2017; Revised August 24, 2017

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.

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References

Rolls-Royce plc., 2016, “Rolls-Royce plc UltrafanTM Engine With Epicyclic Gearbox,” Rolls-Royce plc., Derby, UK, accessed Nov. 16, 2016, https://www.flickr.com/photos/rolls-royceplc/14151477988/in/album-72157644584413758/
Townsend, D. P. , 1991, Dudley's Gear Handbook, 2nd ed., McGraw-Hill, New York.
Karaman, T. , 1921, “Über Laminare Und Turbulente Reibung,” Z. Angew. Math. Mech., 1(4), pp. 233–252. [CrossRef]
Daily, J. , and Nece, R. , 1958, “Roughness and Chamber Dimension Effects on Induced Flow and Frictional Resistance of Enclosed Rotating Disks,” Massachusetts Institute of Technology, Cambridge, MA, Technical Report No. 27.
Dorfman, L. A. , 1963, Hydrodynamic Resistance and Heat Loss of Rotating Solids, Oliver & Boyd, Edinburgh, UK.
Owen, J. M. , and Rogers, R. H. , 1989, Flow and Heat Transfer in Rotating-Disc-Systems: Rotor-Stator Systems, Vol. 1, Research Studies Press Ltd., Taunton, UK.
Reynolds, O. , 1886, “On the Theory of Lubrication and Its Application to Mr. Beauchamp Tower's Experiments, Including an Experimental Determination of the Viscosity of Olive Oil,” Philos. Trans. R. Soc. London, 177, pp. 154–234.
Fraser, R. P. , Dombrowski, N. , and Routley, J. H. , 1963, “The Filming of Liquids by Spinning Cups,” Chem. Eng. Sci., 18(6), pp. 323–337. [CrossRef]
Hinze, J. O. , and Milborn, H. , 1950, “Atomization of Liquids by Means of a Rotating Cup,” ASME J. Appl. Mech., 17(2), pp. 145–153.
Liu, J. , Yu, Q. , and Guo, Q. , 2012, “Experimental Investigation of Liquid Disintegration by Rotary Cups,” Chem. Eng. Sci., 73, pp. 44–50. [CrossRef]
Kamiya, T. , and Kayano, A. , 1972, “Film-Type Disintegration by Rotating Disk,” J. Chem. Eng. Jpn., 5, pp. 174–182. [CrossRef]
Glahn, A. , Busam, S. , Blair, M. F. , Allard, K. L. , and Wittig, S. , 2002, “Droplet Generation by Disintegration of Oil Films at the Rim of a Rotating Disk,” ASME J. Eng. Gas Turbines Power, 124(1), pp. 117–124. [CrossRef]
Szeri, A. Z. , 1980, Tribology: Friction, Lubrication and Wear, Hemisphere, Washington, DC.
Taylor, G. I. , 1923, “Stability of a Viscous Liquid Contained Between Two Rotating Cylinders,” Philos. Trans. R. Soc. Lond. A, 223(605–615), pp. 289–343. [CrossRef]
Theodorsen, T. , and Regier, A. , 1944, “Experiments on Drag of Revolving Disks, Cylinders, and Streamline Rods at High Speeds,” National Advisory Committee for Aeronautics, Washington, DC, Report No. NACA-TR-793. https://ntrs.nasa.gov/search.jsp?R=20050241738
ANSYS, 2013, “ANSYS Fluent User's Guide,” ANSYS Inc., Canonsburg, PA.
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Figures

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Fig. 6

Liquid disintegration from a rotating cup with d = 128 mm and the following liquid properties: ρ = 1170 kg/m3, σ = 0.0488 N/m and μ = 0.072 kg/(ms) according to Ref. [10]. (a) direct droplet formation, Ω = 30.06 rad/s, V˙ = 0.00249 l/s, (b) ligament formation, Ω = 45.95 rad/s, V˙ = 0.0235 l/s, and (c) sheet formation, Ω = 67.05 rad/s, V˙ = 0.0235 l/s. (Figure used with permission from Liu et al. [10].)

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Fig. 5

Detail A of planet gear (Fig. 4) with possible exit flow directions (a, b)

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Fig. 4

Simple journal bearing model with axially and circumferentially constant lubricating gap height h0 and possible exit flow directions (a, b)

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Fig. 3

Epicyclic gearbox in star configuration

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Fig. 2

Epicyclic gearbox in planetary configuration

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Fig. 1

Rolls-Royce Ultrafan™ engine with epicyclic gearbox [1]

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Fig. 7

CFD model of domain of interest

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Fig. 8

Simplified CFD model of domain of interest

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Fig. 9

Fully developed velocity profiles in lubricating gap with k–ω SST turbulence model in the axial (a) and circumferential and (b) directions

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Fig. 12

CFD sector model results for T = 70 °C with boundary conditions and parameter settings as specified in the Appendix, Table 3. Displayed isosurface indicates 50% cell oil volume content. Mesh with Ncells,total = 773 k (Fig. 11(b1)).

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Fig. 10

CFD sector model results for T = 30 °C with boundary conditions and parameter settings as specified in the Appendix, Table 3 in full view (a) and detail view (b). Displayed isosurface indicates 50% cell oil volume content.

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Fig. 11

CFD sector model results for T = 30 °C with boundary conditions and parameter settings as specified in the Appendix, Table 3 for different mesh densities. Displayed isosurface indicates 50% cell oil volume content. (a) Sector size: 10 deg—Ncells,2D = 9.2 k, Ncells,Φ = 24, Ncells,total =221 k, t1 = 0.100 mm, Ncells,oil,d1 = 2, Nlig/10 deg = 5,d1: sharp edge, (b1) sector size: 20 deg—Ncells,2D = 13.1 k, Ncells,Φ = 59, Ncells,total = 773 k, t1 = 0.010 mm, Ncells,oil,d1 = 8, Nlig/10 deg = 5, d1: sharp edge, (b2) sector size: 20 deg—Ncells,2D = 13.1k, Ncells,Φ = 59, Ncells,total = 773 k, t1 = 0.010 mm, Ncells,oil,d1 = 8, Nlig/10 deg = 6, d1: 0.3 mm radius, and (c) sector size: 15 deg—Ncells,2D =54.3 k, Ncells,Φ = 79, Ncells,total = 4300 k, t1 = 0.005 mm, Ncells,oil,d1 = 16, Nlig /10 deg = 5, d1: sharp edge.

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