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Research Papers: Gas Turbines: Aircraft Engine

Study of Gas/Liquid Behavior Within an Aeroengine Bearing Chamber

[+] Author and Article Information
Stephen Pickering

University Technology Centre for Gas Turbine Transmission Systems,
University of Nottingham,
University Park,
Nottingham NG7 2RD, UK

Steven H. Collicott

School of Aeronautics and Astronautics,
Purdue University,
West Lafayette, IN 47907-2045

Nikolas Wiedemann

Rolls-Royce plc, Derby, DE24 8BJ, UK

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Engineering for Gas Turbines and Power. Manuscript received August 8, 2012; final manuscript received August 9, 2012; published online April 18, 2013. Editor: Dilip R. Ballal.

J. Eng. Gas Turbines Power 135(5), 051201 (Apr 18, 2013) (11 pages) Paper No: GTP-12-1319; doi: 10.1115/1.4007753 History: Received August 08, 2012; Revised August 09, 2012

Aeroengine bearing chambers typically contain bearings, seals, shafts and static parts. Oil is introduced for lubrication and cooling and this creates a two phase flow environment that may contain droplets, mist, film, ligaments, froth or foam and liquid pools. Some regions of the chamber contain a highly rotating air flow such that there are zones where the flow is gravity dominated and zones where it is rotation dominated. The University of Nottingham Technology Centre in Gas Turbine Transmission Systems, is conducting an ongoing experimental program investigating liquid and gas flow behavior in a relevant highly rotating environment. Previously reported work by the UTC has investigated film thickness and residence volume within a simplified chamber consisting of outer cylindrical chamber, inner rotating shaft and cuboid off-take geometry (termed the generic deep sump). Recently, a more aeroengine relevant bearing chamber offtake geometry has been studied. This geometry is similar to one investigated at Purdue University and consists of a “sub-sump” region approached by curved surfaces linked to the bearing chamber. The test chamber consists of an outer, stationary cylinder with an inner rotating shaft. The rig runs at ambient pressure and the working fluid (water) is introduced either via a film generator on the chamber wall or through holes in the shaft. In addition to visual data (high speed and normal video), liquid residence volume within the chamber and film thickness were the two numerical comparators chosen. Data was obtained for a number of liquid supply rates, scavenge ratios and shaft rotation speeds. The data from the current model is compared to that from the earlier studies. The data shows that in contrast to the previously reported generic deep sump study, the residence volume of the curved wall deep sump (CWDS) designs is far less sensitive to shaft speed, liquid supply rate and scavenge ratio. The method of liquid supply only makes a significant difference at the lowest scavenge ratios. Residence volume data for the Nottingham CWDS is comparable, when appropriately scaled, to that for the Purdue design. The film thickness data shows that at the lower shaft speeds investigated the flow is gravity dominated whereas at higher shaft speeds shear dominates.

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References

Chandra, B., Simmons, K., Pickering, S., and Tittel, M., 2010, “Factors Affecting Oil Removal From an Aeroengine Bearing Chamber,” Proc. of ASME Turbo Expo 2010, Glasgow, UK, June 14–18, ASME Paper No. GT2010-22631. [CrossRef]
Chandra, B., Simmons, K., Pickering, S., and Tittel, M., 2011, “Liquid and Gas Flow Behaviour in a Highly Rotating Environment,” Proc. of ASME Turbo Expo 2011, Vancouver, Canada, June 6–10, ASME Paper No. GT2011-46430. [CrossRef]
Wittig, S., Glahn, A., and Himmelsbach, J., 1994, “Influence of High Rotational Speeds on Heat Transfer and Oil Film Thickness in Aero-Engine Bearing Chambers,” ASME J. Eng. Gas Turbines and Power, 116, pp. 395–401. [CrossRef]
Glahn, A., and Wittig, S., 1996, “Two-Phase Air/Oil Flow in Aero Engine Bearing Chambers: Characterization of Oil Film Flows,” ASME J. Eng. Gas Turbines and Power, 118, pp. 578–583. [CrossRef]
Gorse, P., Busam, S., and Dullenkopf, K., 2006, “Influence of Operating Condition and Geometry on the Oil Film Thickness in Aeroengine Bearing Chambers,” ASME J. Eng. Gas Turbines and Power, 128, pp. 103–110. [CrossRef]
Glahn, A., Kurreck, M., Willmann, M., and Wittig, S., 1996, “Feasibility Study on Oil Droplet Flow Investigations Inside Aero Engine Bearing Chambers—PDPA Techniques in Combination With Numerical Approaches,” ASME J. Eng. Gas Turbines and Power, 118, pp. 749–755. [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, pp. 117–124. [CrossRef]
Willenborg, K., Busam, S., Roßkamp, H., and Wittig, S., 2002, “Experimental Studies of the Boundary Conditions Leading to Oil Fire in the Bearing Chamber and in the Secondary Air System of Aeroengines,” ASME Turbo EXPO (GT2002), Amsterdam, The Netherlands, June 3–6, ASME Paper No. GT2002-30241. [CrossRef]
Chandra, B., 2006, “Flows in Turbine Engine Oil Sumps,” Ph.D. thesis, Purdue University, Lafayette, IN.

Figures

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Fig. 1

CWDS on test at Purdue 3, inlet liquid (water) flow rate of 1.1 lpm, a shaft speed of 10 000 rpm, and a scavenge ratio of 1.5

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Fig. 2

Nottingham Scavenge test rig

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Fig. 3

Schematic representation of the water-air circuit

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Fig. 4

Angular (θ) and axial (z) measurement origins

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Fig. 5

Normalized residence volumes of Nottingham and Purdue curved wall deep sumps

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Fig. 6

Liquid injection system, Purdue CWDS

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Fig. 7

Generic deep sump geometry [1,2]

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Fig. 8

Normalized residence volumes of CWDS compared to generic deep sump—liquid injection via FG in both cases

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Fig. 9

Off-take void fraction of CWDS with FG

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Fig. 10

Off-take void fraction of CWDS with RID

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Fig. 11

Contours of nondimensional film thickness δ* for CWDS with FG (SR = 3.7, 120 lpm/m flow rate, 15,000 rpm shaft speed). (a) δ* contour range 0 to 0.01 illustrating that there is only small variation in film thickness. (b) δ* contour range 0.001 to 0.004 illustrating that film thickens a little towards front and rear walls and sump entrance.

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Fig. 12

Nondimensional wall film thickness of CWDS with FG

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Fig. 13

Illustrating effect of scavenge ratio on implied film velocity

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Fig. 14

Illustrating effect of liquid supply rate on implied film velocity

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Fig. 15

Contours of nondimensional film thickness δ* for CWDS with RID (flow rate 80 lpm/m, scavenge ratio 4 and 10,000 rpm shaft speed). (a) δ* contour range 0 to 0.01 illustrating that there is only small variation in film thickness. (b) δ* contour range 0.001 to 0.004 illustrating that film is thicker away from front and rear walls, no thickening towards sump entrance.

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Fig. 16

Wall film thickness of CWDS with RID

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Fig. 17

Implied wall film velocity of CWDS with RID

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Fig. 18

With fluid introduction via film generator, incoming flow stays attached to the curved wall (120 lpm/m, SR = 3, 15,000 rpm shaft speed)

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Fig. 19

With fluid introduction via RID incoming flow may overshoot and splash upwards (120 lpm/m, SR = 3.8, 15,000 rpm shaft speed)

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Fig. 20

Film generator (FG)

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Fig. 21

RID schematic drawing and photograph of the RID spindle

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Fig. 22

Residence volume and void fraction measurements procedure

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