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TECHNICAL PAPERS: Gas Turbines: Structures and Dynamics

Unbalance Response of Rotors Supported on Hydrodynamic Bearings Placed Close to Nodal Points of Excited Vibration Modes

[+] Author and Article Information
Demetrio C. Zachariadis

Department of Mechanical Engineering, Polytechnic School, University of São Paulo, Av. Prof. Mello Moraes 2231, São Paulo 05508-900, Brazildczachar@usp.br

J. Eng. Gas Turbines Power 128(3), 661-669 (Mar 01, 2002) (9 pages) doi:10.1115/1.2132381 History: Received December 01, 2001; Revised March 01, 2002

The traditional 8-coefficient bearing model, used in linear rotor dynamics, is shown here to be inadequate for the unbalance response calculation of rotor systems supported on hydrodynamic journal bearings placed close to nodal points of excited modes of vibration. In such situations, one cannot neglect the time varying tilt angle between journals and bearings, whose consideration leads to the adoption of a 32-coefficient bearing model. Numerical results indicate that the differences between vibration amplitudes calculated using both bearing models can be greater than 100%, while discrepancies in the predicted stability thresholds are small. The conclusions of the study are coherent with previously published theoretical and experimental results.

Copyright © 2006 by American Society of Mechanical Engineers
Topics: Bearings , Rotors , Vibration
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References

Figures

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Figure 1

Rotor system model

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Figure 2

Unbalance excitations

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Figure 3

Moments around axes Y and Z; —, this work; ---, results taken from Fig. 7(b) in (15); So, Sommerfeld N#

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Figure 4

Nondimensional stiffness coefficients; lines, this work; points, data taken from Fig. 8 in (7); ε, journal’s relative eccentricity

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Figure 5

Campbell diagram, rotor a

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Figure 6

Campbell diagram, rotor b

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Figure 7

Campbell diagram, rotor c

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Figure 8

Campbell diagram, rotor d

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Figure 9

Vibration mode, rotor a, p≈ωr=35.0rps

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Figure 10

Vibration mode, rotor a, p≈ωr=61.0rps

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Figure 11

Vibration mode, rotor a, p≈ωr=78.0rps

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Figure 12

Vibration mode, rotor a, p≈ωr=81.0rps

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Figure 13

Vibration mode, rotor b, p≈ωr=62.0rps

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Figure 14

Vibration mode, rotor b, p≈ωr=79.0rps

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Figure 15

Vibration mode, rotor c, p≈ωr=62.8rps

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Figure 16

Vibration mode, rotor c, p≈ωr=78.0rps

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Figure 17

Vibration mode, rotor d, p≈ωr=110.0rps.

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Figure 18

Amplification factors, rotor a, disk I, load 1

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Figure 19

Amplification factors, rotor a, disk II, load 1

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Figure 20

Amplification factors, rotor a, disk II, load 2

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Figure 21

Amplification factors, rotor a, disk I, load 3

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Figure 22

Amplification factors, rotor b, disk I, load 3

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Figure 23

Amplification factors, rotor b, disk II, load 3

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Figure 24

Amplification factors, rotor c, disk II, load 3

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Figure 25

Amplification factors, rotor d, disk I, load 4

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Figure 26

Amplification factors, rotor d, disk II, load 4

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Figure 27

Amplification factors, rotor d, disk III, load 4

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Figure 28

Comparison between experimental (Kikuchi (5)) and numerical results

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Figure 29

Vibration mode, tested laboratory rotor

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