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Research Papers: Gas Turbines: Structures and Dynamics

Improving Tilting-Pad Journal Bearing Predictions—Part II: Comparison of Measured and Predicted Rotor-Pad Transfer Functions for a Rocker-Pivot Tilting-Pad Journal Bearing

[+] Author and Article Information
Jason C. Wilkes

Research Engineer
Southwest Research Institute,
San Antonio, TX, 78238
e-mail: jason.wilkes@swri.org

Dara W. Childs

Leland T. Jordan
Prof. of Mechanical Engineering,
Turbomachinery Laboratory,
Texas A&M University,
College Station, TX, 77802
e-mail: dchilds@tamu.edu

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES and POWER. Manuscript received July 2, 2012; final manuscript received July 5, 2012; published online December 4, 2012. Editor: Dilip R. Ballal.

J. Eng. Gas Turbines Power 135(1), 012503 (Dec 04, 2012) (11 pages) Paper No: GTP-12-1250; doi: 10.1115/1.4007368 History: Received July 02, 2012; Revised July 05, 2012

As described in Part I (Wilkes et al., 2012, “Improving Tilting-Pad Journal Bearing Predictions—Part I: Model Development and Impact of Rotor Excited Versus Bearing Excited Impedance Coefficients,” ASME J. Eng. Gas Turb. Power, 135(1), p. 012503), most analytical models for tilting-pad journal bearing (TPJBs) are based on the assumption that explicit dependence on pad motion can be eliminated by assuming harmonic rotor motion such that the amplitude and phase of pad motions resulting from radial and transverse rotor motions are predicted by rotor-pad transfer functions. In short, these transfer functions specify the amplitude and phase of pad motion (angular, radial, translational, etc.) in response to an input rotor motion. Direct measurements of pad motion during test excitation were recorded to produce measured transfer functions between rotor and pad motion, and a comparison between these measurements and predictions is given. Motion probes were added to the loaded pad (having the static load vector directed through its pivot) of a 5-pad TPJB to obtain accurate measurement of pad radial and tangential motion, as well as tilt, yaw, and pitch. Strain gauges were attached to the side of the loaded pad to measure static and dynamic bending strains, which were then used to determine static and dynamic changes in pad curvature (pad clearance).

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References

Adams, M., and Payandeh, S., 1983, “Self-Excited Vibration of Statically Unloaded Pads in Tilting-Pad Journal Bearings,” ASME J. Lubr. Technol., 105, pp. 377–384. [CrossRef]
Sabnavis, G., 2005, “Test Results for Shaft Tracking Behavior of Pads in a Spherical Pivot Type Tilting Pad Journal Bearing,” M.S. thesis, Virginia Polytechnic Institute and State University, Blacksburg, VA.
Wilkes, J., 2011, “Measured and Predicted Transfer Functions Between Rotor Motion and Pad Motion for a Rocker-Back Tilting-Pad Bearing in LOP Configuration,” Proc. of ASME Turbo Expo 2011, Vancouver, Canada, June 6–10, ASME Paper No. GT2011-46510. [CrossRef]
Lund, J. W., 1964, “Spring and Damping Coefficients for the Tilting-Pad Journal Bearing,” ASLE Trans., 7, pp. 342–352. [CrossRef]
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Lund, J. W., and Pedersen, L. B., 1987, “The Influence of Pad Flexibility on the Dynamic Coefficients of a Tilting Pad Journal Bearing,” ASME J. Tribol., 109(1), pp. 65–70. [CrossRef]
Wilkes, J., and Childs, D., 2012, “Improving Tilting-Pad Journal Bearing Predictions—Part I: Model Development and Impact of Rotor Excited Versus Bearing Excited Impedance Coefficients,” ASME J. Eng. Gas Turb. Power, 135(1), p. 012503.
Rodriguez, L., and Childs, D., 2006, “Frequency Dependency of Measured and Predicted Rotordynamic Coefficients for Load-on-Pad Flexible-Pivot Tilting-Pad Bearing,” ASME J. Tribol., 128(2), pp. 388–395. [CrossRef]
Carter, C., and Childs, D., 2008 “Measurements Versus Predictions for the Rotordynamic Characteristics of a 5-Pad, Rocker-Pivot, Tilting-Pad Bearing in Load Between Pad Configuration,” Proc. of ASME Turbo Expo 2008, Berlin, Germany, June 9–13, ASME Paper No. GT2008-50069. [CrossRef]
Harris, J., and Childs, D., 2008, “Static Performance Characteristics and Rotordynamic Coefficients for a Four-Pad Ball-In-Socket Tilting Pad Journal Bearing,” Proc. of ASME Turbo Expo 2008, Berlin, Germany, June 9–13, ASME Paper No. GT2008-50063. [CrossRef]
Kulhanek, C., 2010, “Dynamic and Static Characteristics of a Rocker-Pivot, Tilting-Pad Bearing with 50% and 60% Offsets,” M.S. thesis, Texas A&M University, College Station, TX.
Wilkes, J., 2011, “Measured and Predicted Rotor-Pad Transfer Functions for a Rocker-Pivot Tilting-Pad Journal Bearing,” Ph.D. dissertation, Texas A&M University, College Station, TX.
Glienicke, J., 1966, “Experimental Investigation of Stiffness and Damping Coefficients of Turbine Bearings and Their Application to Instability Predictions,” Proc. of the International Mech. E., Vol. 181(3B), pp. 116–129.
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Wilkes, J., and Childs, D., 2012, “Tilting-Pad Journal Bearings—A Discussion on Stability Calculation, Frequency Dependence, and Pad and Pivot Flexibility,” Proc. of ASME Turbo Expo 2012, Copenhagen, Denmark, June 11–15, Paper No. GT2012-69809.
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Figures

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Fig. 1

Drawing of the test rig [11]

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Fig. 2

Stator and test bearing viewed from the nondrive end

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Fig. 3

Primary pad degrees of freedom

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Fig. 4

Proximity probe orientation on loaded pad

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Fig. 5

Configuration of strain gauges applied to the loaded pad

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Fig. 6

Properties of the measured TF amplitudes of the loaded pad due to (a) transverse (ηj) and (b) radial (ξj) rotor motions at 4400 rpm and 1566 kPa unit load (UL)

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Fig. 7

Measured TF amplitudes of the loaded pad due to (a) transverse (ηj) and (b) radial (ξj) rotor motions at 4400 rpm at zero, medium and high unit loads

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Fig. 8

Measured and predicted pad-rotor TF amplitudes of the loaded pad due to (a) transverse (ηj) and (b) radial (ξj) rotor motions at 4400 rpm and 0 kPa (0 psi) UL

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Fig. 9

Measured and predicted pad-rotor TF amplitudes of the loaded pad due to (a) transverse (ηj) and (b) radial (ξj) rotor motions at 4400 rpm and 3132 kPa (454 psi) UL

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Fig. 10

Measured and predicted pad-rotor TF amplitudes of the loaded pad due to (a) transverse (ηj) and (b) radial (ξj) rotor motions at 4400 rpm and 1566 kPa (227 psi) UL

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Fig. 11

Measured TF amplitudes of the loaded pad due to (a) transverse (ηj) and (b) radial (ξj) rotor motions at 4400 rpm at various unit loads

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Fig. 12

Measured and predicted pad-rotor TF amplitudes of the loaded pad due to (a) transverse (ηj) and (b) radial (ξj) rotor motions at 4400 rpm and 3132 kPa (454 psi) UL

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Fig. 13

Waterfall plot of normalized pad tilt response due to test excitations at 4400 rpm and 3132 kPa unit load

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Fig. 14

Measured TF amplitudes of the loaded pad due to (a) transverse (ηj) and (b) radial (ξj) rotor motions at 10,200 rpm at zero, medium and high unit loads

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Fig. 15

Measured and predicted rotor-pad TF amplitudes of the loaded pad due to (a) transverse (ηj) and (b) radial (ξj) rotor motions at 10,200 rpm and 3132 kPa (454 psi) UL

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