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Research Papers: Hydrodynamic Lubrication

Steady-State Tilting-Pad Bearing Performance Under Reduced Oil Supply Flow Rates

[+] Author and Article Information
Bradley R. Nichols

Rotating Machinery and Controls Laboratory,
Department of Mechanical and
Aerospace Engineering,
University of Virginia,
Charlottesville, VA 22904;
Rotor Bearing Solutions International,
Charlottesville, VA 22911
e-mails: brn7 h@virginia.edu;
brad.nichols@rotorsolution.com

Roger L. Fittro

Rotating Machinery and Controls Laboratory,
Department of Mechanical and
Aerospace Engineering,
University of Virginia,
Charlottesville, VA 22904
e-mail: fittro@virginia.edu

Christopher P. Goyne

Rotating Machinery and Controls Laboratory,
Department of Mechanical and
Aerospace Engineering,
University of Virginia,
Charlottesville, VA 22904
e-mail: goyne@virginia.edu

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received August 15, 2017; final manuscript received January 31, 2018; published online April 3, 2018. Assoc. Editor: Alan Palazzolo.

J. Tribol 140(5), 051701 (Apr 03, 2018) (8 pages) Paper No: TRIB-17-1317; doi: 10.1115/1.4039408 History: Received August 15, 2017; Revised January 31, 2018

Reduced oil supply flow rates in fluid film bearings can cause cavitation, or lack of a fully developed hydrodynamic film layer, at the leading edge of the bearing pads. Reduced oil flow has the well-documented effects of higher bearing operating temperatures and decreased power losses and is commonly referred to as starvation. This study looks at the effects of oil supply flow rate on steady-state bearing performance and provides increased experimental data for comparison to computational predictions. Tests are conducted on a five-pad tilting-pad bearing positioned in a vintage, flooded housing with oil supply nozzles. Pad temperatures, sump temperature, journal operating position, and motor input power are measured at various operating speeds ranging from 2000 to 12,000 rpm and various oil supply flow rates. Predicted results are obtained from bearing modeling software based on thermoelastohydrodynamic (TEHD) lubrication theory. A starved flow model was previously developed as an improvement over the original flooded flow model to more accurately capture bearing behavior under reduced flow conditions. Experimental results are compared to both flow models. The starved bearing model predicts significantly higher journal operating positions than the flooded model and shows good correlation with the experimental data. Predicted pressure profiles from the starved bearing model show cavitation of the upper unloaded pads that increase in severity with increasing speed and decreasing oil supply flow rate. The progressive unloading of these top pads explains the rise in shaft centerline position and helps further validate the starvation model.

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References

Fillon, M. , Bilgoud, J. C. , and Frene, J. , 1992, “ Experimental Study of Tilting-Pad Journal Bearings—Comparison With Theoretical Thermoelastohydrodynamic Results,” ASME J. Tribol., 114(3), pp. 579–587. [CrossRef]
Dmochowski, W. , Brockwell, K. , DeCamillo, S. , and Mikula, A. , 1993, “ A Study of the Thermal Characteristics of the Leading Edge Groove and Conventional Tilting Pad Journal Bearings,” ASME J. Tribol., 115(2), pp. 219–226. [CrossRef]
Simmons, J. E. L. , and Dixon, S. J. , 1994, “ Effect of Load Direction, Preload, Clearance Ratio, and Oil Flow on the Performance of a 200 mm Journal Pad Bearing,” Tribol. Trans., 37(2), pp. 227–236. [CrossRef]
Bouchoule, C. , Fillon, M. , Nicolas, D. , and Barresi, F. , 1996, “ Experimental Study of Thermal Effects in Tilting Pad Journal Bearings at High Operating Speeds,” ASME J. Tribol., 118(3), pp. 532–538. [CrossRef]
Harangozo, A. V. , Stolarski, T. A. , and Gozdawa, R. J. , 1991, “ The Effect of Different Lubrication Methods on the Performance of a Tilting-Pad Journal Bearing,” Tribol. Trans., 34(4), pp. 529–536. [CrossRef]
Tanaka, M. , 1991, “ Thermohydrodynamic Performance of a Tilting Pad Journal Bearing With Spot Lubrication,” ASME J. Tribol., 113(3), pp. 615–619. [CrossRef]
Fillon, M. , Bilgoud, J. C. , and Frene, J. , 1993, “ Influence of the Lubricant Feeding Method on the Thermoelastohydrodynamic Characteristics of Tilting-Pad Journal Bearings,” Sixth International Conference on Tribology, Budapest, Hungary, Aug. 30–Sept. 2, pp. 7–10.
Brockwell, K. , Dmochowski, W. , and DeCamillo, S. , 1994, “ Analysis and Testing of LEG Tilting Pad Journal Bearing—A New Design for Increasing Load Capacity, Reducing Operating Temperatures and Conserving Energy,” 23rd Turbomachinery Symposium, Dallas, TX, Sept. 13–15, pp. 43–56.
DeCamillo, S. , and Brockwell, K. , 2001, “ A Study of Parameters That Affect Pivoting Shoe Journal Bearing Performance in High-Speed Turbomachinery,” 30th Turbomachinery Symposium, College Station, TX, pp. 9–22.
Dmochowski, W. , and Blair, B. , 2006, “ Effect of Oil Evacuation on the Static and Dynamic Properties of Tilting Pad Journal Bearings,” Tribol. Trans., 49(4), pp. 536–544. [CrossRef]
Nicholas, J. C. , 1994, “ Tilting Pad Bearing Design,” 23rd Turbomachinery Symposium, College Station, TX, Dallas, TX, Sept. 13–15, pp. 179–194.
Nicholas, J. C. , 2003, “ Tilting Pad Journal Bearings With Spray-Bar Blockers and By-Pass Cooling for High Speed, High Load Applications,” 32nd Turbomachinery Symposium, College Station, TX, Sept. 8–11, pp. 27–37.
He, M. , 2003, “Thermoelastohydrodynamic Analysis of Fluid Film Journal Bearings,” Ph.D. dissertation, University of Virginia, Charlottesville, VA.
He, M. , Allaire, P. E. , Barrett, J. , and Nicholas, J. C. , 2005, “ Thermohydrodynamic Modeling of Leading-Edge Groove Bearings Under Starved Conditions,” Tribol. Trans., 48(3), pp. 362–369. [CrossRef]
Cloud, C. H. , 2007, “Stability of Rotors Supported on Tilting-Pad Journal Bearings,” Ph.D. dissertation, University of Virginia, Charlottesville, VA.
Nicholas, J. C. , Elliott, G. , Shoup, T. P. , and Martin, E. , 2008, “ Tilting Pad Journal Bearing Starvation Effects,” 37th Turbomachinery Symposium, Houston, TX, Sept. 8–11, pp. 1–10.
Nichols, B. R. , Fittro, R. L. , and Goyne, C. P. , 2017, “ Subsynchronous Vibration Patterns Under Reduced Oil Supply Flow Rates,” ASME J. Eng. Gas Turbines Power, in press.

Figures

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Fig. 2

Test bearing in flooded, pressurized housing [15]

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Fig. 3

Flooded, pressurized housing oil flow path features [11]

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Fig. 4

Test bearing thermocouple locations [15]

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Fig. 5

Groove mixing and hot-oil carryover concepts [11]

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Fig. 6

TC 5L measured and predicted temperatures

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Fig. 7

TC 5T measured and predicted temperatures

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Fig. 8

TC 4T measured and predicted temperatures

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Fig. 9

TC 1L measured and predicted temperatures

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Fig. 10

Measured and predicted sump temperatures

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Fig. 11

Measured and predicted vertical operating positions (2000 rpm, 0.3 eccentricity ratio reference)

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Fig. 12

Percentage power change with oil supply flow rate

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Fig. 17

Predicted pressure profiles versus flow rate, 10,000 rpm, starved model (627 kPa max)

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Fig. 16

Predicted pressure profiles versus flow rate, 10,000 rpm, flooded model (696 kPa max)

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Fig. 15

TC 4T hot-oil carryover sensitivity (flooded model, 3.79 lpm)

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Fig. 14

Predicted pressure profiles versus speed, nominal flow rate, starved model (581 kPa max)

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Fig. 13

Predicted pressure profiles versus speed, nominal flow rate, flooded model (710 kPa max)

Tables

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