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Research Papers: Gas Turbines: Structures and Dynamics

An Experimental Study of the Load-Orientation Sensitivity of Three-Lobe Bearings

[+] Author and Article Information
Rasish Khatri

Development Engineer,
Calnetix Technologies,
Cerritos, CA 90703

Dara W. Childs

Leland T. Jordan Professor of Mechanical Engineering,
Turbomachinery Laboratory,
College Station, TX 77843

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 10, 2014; final manuscript received August 15, 2014; published online November 11, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(4), 042503 (Apr 01, 2015) (9 pages) Paper No: GTP-14-1356; doi: 10.1115/1.4028662 History: Received July 10, 2014; Revised August 15, 2014; Online November 11, 2014

Static and dynamic performance test results are provided for a three-lobe bearing evaluated over the following range of radial static-load orientations (taken from the leading edge of the loaded pad): 0 deg, 20 deg, 30 deg, 40 deg, 60 deg, 80 deg, 90 deg, and 100 deg. Static and dynamic test results are evaluated to determine the sensitivity of the bearing to changes in the static load direction. The bearing has the following specifications: 100 deg arc angle, 0.52 preload, 70% offset, 101.74 mm minimum bore diameter, 0.116 mm radial pad clearance, and 76.3 mm axial length. The bearing is tested at 6750 rpm, 9000 rpm, 10,800 rpm, and 13,200 rpm, and at five different unit loads. Static measurements include hot and cold clearances, static eccentricities, and pad metal temperatures. Dynamic results include stiffness coefficients, damping coefficients, and whirl-frequency ratios (WFRs). Dynamic tests show that the three-lobe bearing is very sensitive to load orientation at low speeds and high loads. Kxx is highest for the 80 deg, 90 deg, and 100 deg load orientations. Kyy is highest for the 20 deg, 30 deg, and 40 deg load orientations. Kxy is highest for the 80 deg, 90 deg, and 100 deg load orientations. The magnitude of Kyx is highest for the 0 deg and 20 deg load orientations. Cxx is largest for the 80 deg, 90 deg, and 100 deg load orientations, and Cyy is largest for the 0 deg, 20 deg, 30 deg, and 40 deg load orientations. In terms of WFRs, it is generally dynamically advantageous to orient the static load vector for this bearing toward the leading edge of the pad. WFRs at 6750 rpm with loads of 1149 kPa, 1723 kPa, and 2298 kPa are equal to zero when the static load vector is pointed toward the leading edge of the pad and between 0.25 and 0.5 when the static load vector is pointed toward the trailing edge of the pad. The bearing is not sensitive to load orientation at high speeds and light loads. At 13,200 rpm, measured WFRs are between 0.2 and 0.6 at all loads and for all load orientations. Measured WFRs at the no-load condition are between 0.3 and 0.6 at all speeds. Static data showed that the 30 deg and 90 deg load orientations yielded slightly higher measured maximum pad-metal-temperature increases at each speed relative to the other load orientations. At the highest static-load magnitudes, the pad metal temperatures are not as dependent on load orientation. The 20 deg, 30 deg, and 40 deg load orientations had the smallest measured eccentricity ratio, and thus the highest static stiffness.

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References

Pinkus, O., 1959, “Analysis and Characteristics of the Three-Lobe Bearing,” ASME J. Basic Eng., 81, pp. 49–55.
Someya, T., ed., 1989, Journal-Bearing Databook, Springer-Verlag, Heidelberg, Germany.
Leader, M. E., Flack, R. D., and Lewis, D. W., 1980, “An Experimental Determination of the Instability of a Flexible Rotor in Four-Lobe Bearings,” Wear, 58(1), pp. 35–47. [CrossRef]
Lanes, R. F., and Flack, R. D., 1982, “Effects of Three-Lobe Bearing Geometries on Flexible-Rotor Stability,” ASLE Trans., 25(3), pp. 377–385. [CrossRef]
Pettinato, B., and Flack, R. D., 2001, “Test Results For a Highly Preloaded Three-Lobe Journal Bearing-Effect of Load Orientation on Static and Dynamic Characteristics,” Lubrication Eng., 57(9), pp. 23–30.
Allaire, P. E., and Flack, R. D., 1981, “Design of Journal Bearings for Rotating Machinery,” Tenth Turbomachinery Symposium, College Station, TX, Dec. 1–3, pp. 25–45.
Nicholas, J., and Moll, R., 1993, “Shifting Critical Speeds Out of the Operating Range by Changing From Tilting Pad to Sleeve Bearings,” Twenty-Second Turbomachinery Symposium, Dallas, TX, Sept. 14–16, pp. 25–32.
Khatri, R., 2013, “An Experimental Investigation of the Static and Dynamic Performance of Horizontal-Application and Vertical-Application Three-Lobe Bearings,” M.S. thesis, Texas A&M University, College Station, TX.
Kaul, A., 1999, “Design and Development of a Test Setup for the Experimental Determination of the Rotordynamic and Leakage Characteristics of Annular Bushing Oil Seals,” M.S. thesis, Texas A&M University, College Station, TX.
Childs, D. W., Delgado, A., and Vannini, G., 2011, “Tilting-Pad Bearings: Measured Frequency Characteristics of their Rotordynamic Coefficients,” Fortieth Turbomachinery Symposium, Houston, TX, Sept. 12–15.
Glienicke, J., 1966, “Experimental Investigation of Stiffness and Damping Coefficients of Turbine Bearings and Their Application to Instability Predictions,” Proc. Inst. Mech. Eng., 181(3B), pp. 116–129. [CrossRef]
Wilkes, J., 2011, “Measured and Predicted Transfer Functions Between Rotor Motion and Pad Motion for a Rocker-Back Tilting-Pad Bearing in LOP Configuration,” Ph.D. thesis, Texas A&M University, College Station, TX.
Childs, D., and Hale, K., 1994, “A Test Apparatus and Facility to Identify the Rotordynamic Coefficients of High-Speed Hydrostatic Bearings,” ASME J. Tribol., 116(2), pp. 337–344. [CrossRef]
Lund, J., 1965, “The Stability of an Elastic Rotor in Journal Bearings With Flexible, Damped Supports,” ASME J. Appl. Mech., 32(4), pp. 911–920. [CrossRef]

Figures

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Fig. 1

Typical geometry of a three-lobe bearing

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Fig. 3

The eight static load orientations tested on a 100 deg arc angle pad of a three-lobe bearing

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Fig. 2

Cross section of test rig [9]

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Fig. 10

Kxx (top) and Kyy (bottom) versus load orientation at 13,200 rpm

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Fig. 4

Measured cold clearance (0 deg load orientation)

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Fig. 5

Measured hot clearance (0 deg load orientation)

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Fig. 6

Pad metal temperature increases versus load orientation at 6750 rpm

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Fig. 7

Pad metal temperature increases versus load orientation at 13,200 rpm

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Fig. 8

Eccentricity ratio versus load orientation at 6750 rpm

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Fig. 9

Kxx (top) and Kyy (bottom) versus load orientation at 6750 rpm

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Fig. 11

Kxx and Kyy (top), absolute orthotropy (middle), and relative orthotropy (bottom) versus load orientation at 6750 rpm/2298 kPa

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Fig. 12

Kxx and Kyy (top) and |KxxKyy| (bottom) versus load orientation at 13,200 rpm/2298 kPa

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Fig. 13

Kxy (top) and Kyx (bottom) versus load orientation at 6750 rpm

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Fig. 14

Kxy (top) and Kyx (bottom) versus load orientation at 13,200 rpm

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Fig. 15

Cxx (top) and Cyy (bottom) versus load orientation at 6750 rpm

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Fig. 16

Cxx (top) and Cyy (bottom) versus load orientation at 13,200 rpm

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Fig. 17

WFR versus load orientation at 6750 rpm

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Fig. 18

WFR versus load orientation at 13,200 rpm

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