0
Research Papers: Gas Turbines: Structures and Dynamics

Rotor Damped Natural Frequencies and Stability Under Reduced Oil Supply Flow Rates to Tilting-Pad Journal Bearings

[+] Author and Article Information
Bradley R. Nichols

Rotating Machinery and Controls Laboratory,
Department of Mechanical and
Aerospace Engineering,
University of Virginia,
Charlottesville, VA 22904
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

1Present address: Rotor Bearing Solutions International, Charlottesville, VA 22901.

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received January 30, 2018; final manuscript received June 29, 2018; published online August 13, 2018. Editor: Jerzy T. Sawicki.

J. Eng. Gas Turbines Power 140(12), 122502 (Aug 13, 2018) (10 pages) Paper No: GTP-18-1036; doi: 10.1115/1.4040813 History: Received January 30, 2018; Revised June 29, 2018

Reduced oil supply flow rates in fluid film bearings can cause cavitation, or lack of a fully developed film layer, over one or more of the pads due to starvation. Reduced oil flow has the well-documented effects of higher bearing operating temperatures and decreased power losses; however, little experimental data are available on its effects on system stability and dynamic performance. The study looks at the effects of oil supply flow rate on dynamic bearing performance by comparing experimentally identified damped natural frequencies and damping ratios to predictive models. A test rig consisting of a flexible rotor and supported by two tilting pad bearings in flooded housings is utilized in this study. Tests are conducted over a range of supercritical operating speeds and bearing loads while systematically reducing the oil supply flow rates provided to the bearings. Shaft response measured as a magnetic actuator is used to perform sine sweep excitations of the rotor. A single-input, multiple-output system identification technique is then used to obtain frequency response functions (FRFs) and modal parameters. All experimental results are compared to predicted results obtained from bearing models based on thermoelastohydrodynamic (TEHD) lubrication theory. Both flooded and starved model flow assumptions are considered and compared to the data. Differences in the predicted trends of the models and the experimental data across varying operating conditions are examined. Predicted pressure profiles and dynamic coefficients from the models are presented to help explain any differences in trends.

Copyright © 2018 by ASME
Your Session has timed out. Please sign back in to continue.

References

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. 3, pp. 7–10.
Brockwell, K. , Dmochowski, W. , and DeCamillo, S. , 1994, “Analysis and Testing of the 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. http://oaktrust.library.tamu.edu/handle/1969.1/163501
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. https://oaktrust.library.tamu.edu/bitstream/handle/1969.1/163327/t30pg009.pdf?sequence=1&isAllowed=y
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]
DeCamillo, S. M. , He, M. , and Cloud, C. H. , 2008, “Journal Bearing Vibration and SSV Hash,” 37th Turbomachinery Symposium, Houston, TX, Sept. 8–11, pp. 11–22. http://oaktrust.library.tamu.edu/handle/1969.1/163128
He, M. , 2003, “Thermoelastohydrodynamic Analysis of Fluid Film Journal Bearings,” Ph.D. dissertation, University of Virginia, Charlottesville, VA. https://elibrary.ru/item.asp?id=5710650
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]
Whalen, J. K. , Cerny, V. , He, M. , and Polerich, V. , 2015, “The Effect of Starvation on the Dynamic Properties of Tilting-Pad Journal Bearings,” 44th Turbomachinery Symposium, Houston, TX, Sept. 14–17, pp. 14–17. http://oaktrust.library.tamu.edu/handle/1969.1/162169
Nichols, B. R. , Fittro, R. L. , and Goyne, C. P. , 2018, “Subsynchronous Vibration Patterns Under Reduced Oil Supply Flow Rates,” ASME J. Eng. Gas Turbines Power, 140(10), p. 102503.
Cloud, C. H. , 2007, “Stability of Rotors Supported on Tilting-Pad Journal Bearings,” Ph.D. Dissertation, University of Virginia, Charlottesville, VA.
Nicholas, J. C. , 1994, “Tilting Pad Bearing Design,” 23rd Turbomachinery Symposium, College Station, TX, Sept. 13–15, pp. 179–194. https://dyrobes.com/wp-content/uploads/2016/04/Tilting-Pad-Bearing-Design-John-C.-Nicholas-199428032016.pdf
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. https://pdfs.semanticscholar.org/bc64/74754c93304c2c67a09d23c902bf2d4ad276.pdf
NI, 2009, “The Fundamentals of FFT-Based Signal Analysis and Measurement in LabVIEW and LabWindows/CVI,” National Instruments, Austin, TX, accessed June 7, 2018, www.ni.com/white-paper/4278/en
Lee, C. , 1991, “A Complex Modal Testing Theory for Rotating Machinery,” Mech. Syst. Signal Process., 5(2), pp. 119–137. [CrossRef]
Kline, S. J. , and McClintock, F. A. , 1953, “Describing Uncertainties in Single-Sample Experiments,” Mech. Eng., 75(1), pp. 3–8.
Barrett, L. E. , Gunter, E. J. , and Allaire, P. E. , 1978, “Optimum Bearing and Support Damping for Unbalance Response and Stability of Rotating Machinery,” ASME J. Eng. Power, 100(1), pp. 89–94. [CrossRef]

Figures

Grahic Jump Location
Fig. 3

Flooded, pressurized housing oil flow path features [11]

Grahic Jump Location
Fig. 2

Test bearing drawing [10]

Grahic Jump Location
Fig. 9

Effect of oil supply flow rate on damping ratio, 124 kPa specific load

Grahic Jump Location
Fig. 8

Effect of bearing load on damping ratio, 100% flow rate

Grahic Jump Location
Fig. 4

Damped natural frequency versus speed, 124 kPa specific load, 100% flow rate

Grahic Jump Location
Fig. 5

Damping ratio versus speed, 124 kPa specific load, 100% flow rate

Grahic Jump Location
Fig. 6

Identified frequency response versus speed, forward mode contribution, Grr, 124 kPa specific load, 100% flow rate

Grahic Jump Location
Fig. 7

Effect of bearing load on damped natural frequency, 100% flow rate

Grahic Jump Location
Fig. 10

Effect of oil supply flow rate on damping ratio, 365 kPa specific load

Grahic Jump Location
Fig. 11

Vertical stiffness and damping coefficients, 124 kPa specific load, 100% flow rate

Grahic Jump Location
Fig. 15

Pressure profiles versus bearing load, 12,000 rpm, 100% flow rate

Grahic Jump Location
Fig. 16

Vertical stiffness coefficients versus oil supply flow rate, 124 kPa specific load

Grahic Jump Location
Fig. 12

Pressure profiles versus operating speed, 124 kPa specific load, 100% flow rate

Grahic Jump Location
Fig. 13

Vertical stiffness coefficients versus load, 100% flow rate

Grahic Jump Location
Fig. 14

Vertical damping coefficients versus load, 100% flow rate

Grahic Jump Location
Fig. 17

Vertical damping coefficients versus oil supply flow rate, 124 kPa specific load

Grahic Jump Location
Fig. 18

Pressure profiles versus oil supply flow rate, 10,000 rpm, 124 kPa specific load

Grahic Jump Location
Fig. 19

Pressure profiles versus oil supply flow rate, 10,000 rpm, 365 kPa specific load

Tables

Errata

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In