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TECHNICAL PAPERS

Numerical and Experimental Investigations on Flexible Multi-bearing Rotor Dynamics

[+] Author and Article Information
Q. Ding

Department of Mechanics,  Tianjin University, Tianjin, 300072, People’s Republic of Chinaqding@public.tpt.tj.cn

A. Y. Leung

Department of Building and Construction,  City University of Hong Kong, Tatchee Avenue, HKSAR, Chinabcaleung@cityu.edu.hk

J. Vib. Acoust 127(4), 408-415 (Jul 07, 2004) (8 pages) doi:10.1115/1.1898336 History: Received December 16, 2003; Revised July 07, 2004

An experimental test rig is built to verify the dynamics of a multi-bearing rotor. It consists of two flexibly coupled shafts and is connected to a motor at one end via a flexible coupling. Each of the shafts is supported at the ends by two hydrodynamic bearings and is attached with two disks with equal and unequal masses, respectively. The mathematical model of the test rig is developed and is simulated numerically. The non-stationary dynamic responses of the system during speed-up with a constant angular acceleration are shown, respectively, by the non-stationary bifurcation diagrams, the selected time flows, and the spectrum cascades. Experiments are then carried out on the test rig. Generally, the numerical results are verified qualitatively by the experiments. Both results indicate that the non-synchronous whirls of the two shafts influence each other when flexibly coupled together. In particular, a new phenomenon is found for the four-bearing rotor system: the pre-existing non-synchronous whirl/whip resulted from the instability of one shaft can activate the onset of oil instability of another shaft. In the theoretical simulation, this phenomenon represents the rapid increase of the non-synchronous whirl orbit, whereas in the experiment, it represents the simultaneous existence of two whirl/whip frequencies in the spectra.

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Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 1

Experimental four-bearing flexible rotor rig

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Figure 2

NBDs of the single-shaft rotors in speed up (α=5rad∕s2)

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Figure 3

NBDs of the multi-bearing rotor in speed up (k4=0.05k3,α=5rad∕s2)

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Figure 4

NBDs of the multi-bearing rotor in speed up (k4=0.01k3,α=5rad∕s2)

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Figure 5

Rapid growth of the whirl orbit of disk 5 (k4=0.01k3,α=5rad∕s2)

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Figure 6

Rapid growth of the half-frequency component of X5(k4=0.01k3,α=5rad∕s2)

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Figure 7

Experimental result of single-shaft 1: spectrum cascade and selected orbits (x2,y2)

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Figure 8

Experimental result of single-shaft 2: spectrum cascades and selected orbits

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Figure 9

Experimental results of multi-bearing rotor: spectrum cascades of disk 2 in whole process and in whirl/whip regime

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Figure 10

Experimental results of multi-bearing rotor: spectrum cascades of disk 5 in whole process and in whirl/whip regime

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Figure 11

Experimental results of multi-bearing rotor: selected orbits of disks 2 and 5

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