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Technical Brief

Structural Stiffness and Damping Coefficients of a Multileaf Foil Bearing With Bump Foils Underneath

[+] Author and Article Information
Ye Tian

e-mail: a.g.o.u2@stu.xjtu.edu.cn

Yanhua Sun

Mem. ASME
e-mail: sunyanhua@mail.xjtu.edu.cn

Lie Yu

e-mail: yulie@mail.xjtu.edu.cn
State Key Laboratory for Strength and Vibration
of Mechanical Structures,
Xi'an Jiaotong University,
Xi'an, Shaanxi Province 710049, China

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 28, 2013; final manuscript received November 13, 2013; published online December 12, 2013. Assoc. Editor: Jerzy T. Sawicki.

J. Eng. Gas Turbines Power 136(4), 044501 (Dec 12, 2013) (8 pages) Paper No: GTP-13-1276; doi: 10.1115/1.4026054 History: Received July 28, 2013; Revised November 13, 2013

This paper presents a multileaf foil bearing (MLFB), which consists of four resilient top foils and four stiff bump foils underneath; thus, a high supporting capacity and a high damping capacity can be achieved. A specially designed test rig is used to identify the structural stiffness and damping coefficients of the MLFB. The rotor of the test rig is supported by two journal MLFBs and a thrust active magnetic bearing (AMB) and the static and dynamic loads are applied by two radial AMBs. The tests on MLFBs were conducted under conditions of no shaft rotation at different angular positions and journal displacements with different excitation frequency. A frequency domain identification method is presented to determine the stiffness and damping coefficients. Static measurements show nonlinear deflections with applied forces, which varies with the orientation of the load angular position. The dynamic measurements show that the stiffness and equivalent viscous damping change with the excitation frequency. Furthermore, the stiffness and damping coefficients are related to the operating position where dynamic load tests were conducted. The investigation provides extensive measurements of the static and dynamic characteristics of the MLFB. These results can serve as a benchmark for the calibration of analytical tools under development.

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Figures

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Fig. 1

Schematic example of journal foil bearings: (a) leaf-type foil bearing, and (b) bump-type foil bearing

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Fig. 2

Schematic of the multileaf foil bearing (MLFB)

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Fig. 3

Schematic of the test rig

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Fig. 4

Load and angular positions

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Fig. 5

Measured static load versus journal displacement. (a) AP0: load on middle of bump strip and (b) AP1: load on edge of bump strip.

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Fig. 6

Static structural stiffness versus journal displacement

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Fig. 7

Test positions and excitation directions

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Fig. 8

Schematic of the dynamic model

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Fig. 10

Measured equivalent viscous damping: (a) cnnf, (b) cttf, (c) cntf, and (d) ctnf

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Fig. 9

Measured structural stiffness: (a) knnf, (b) kttf, (c) kntf;, and (d) ktnf

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