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TECHNICAL PAPERS

Experimental Investigation Into the Effect of Fluid Viscosity on Instability of an Over-hung Flexible Rotor Partially Filled With Fluid

[+] Author and Article Information
Zhu Changsheng

College of Electrical Engineering, Zhejiang University, 310027 Hangzhou, Zhejiang, The People’s Republic of Chinacszhu@hotmail.com

J. Vib. Acoust 128(3), 392-401 (Jun 01, 2006) (10 pages) doi:10.1115/1.2166857 History:

The effect of fluid viscosity on the developing process of the instability in an over-hung flexible rotor partially filled with fluid, the dynamical behavior of the rotor system while the instability occurs, the unstable region of rotational speeds, and the whirl frequency of the rotor system in the unstable region of rotational speeds, are experimentally investigated in this paper. It is shown that when the rotational speed is just over the reduced first critical speed of the fluid-filled rotor system that is less than the first critical speed of empty rotor system, the unstable motion occurs. The rotor system in the unstable speed region does not whirl at either a constant rotational speed or the first critical speed of the empty rotor system, the whirl frequency of the rotor system in the unstable speed region, dominated by the fluid-filled ratio and weakly depending on the viscosity of fluid, linearly increases with the rotational speed. There exists a hysteresis range of rotational speeds at the upper bound of the unstable speed region, which is not caused by the rotor transient motion when passing through the unstable speed region. As the fluid viscosity increases, both the unstable speed region and the hysteresis region narrow. The influence of the fluid viscosity on the unstable speed region of a rotor filled with a high viscosity fluid must be considered.

FIGURES IN THIS ARTICLE
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Copyright © 2006 by American Society of Mechanical Engineers
Topics: Fluids , Viscosity , Rotors , Whirls , Motion
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Figures

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Figure 1

A schematic of the flexible rotor experimental rig (all dimensions in mm)

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Figure 7

Effect of the fluid viscosity on the unstable speed region: Water (엯), Shell 4113 oil (◻), Shell 13 oil (◇), Shell 37 oil (▵)

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Figure 8

Theoretical and experimental unstable speed region of the rotor system: Water (엯), Shell 37 oil (◻), 2D viscous fluid model (◇), 2D inviscid fluid model, and quasi-3D inviscid fluid model (▶ ▿)

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Figure 9

The variation of the nondimensional whirl frequency of rotor with the rotational speed in run-up and run-down operations (H=0.383 water), run-up (엯), run-down (●), error line (---)

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Figure 10

The variation of the nondimensional whirl frequency with the rotational speed for different kinds of fluids. H=0.069 (엯), H=0.196 (◻), H=0.383 (◇), H=0.502 (▿). (a) Water, (b) Shell 4113 oil, (c) Shell 13 oil, and (d) Shell 37 oil.

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Figure 11

The effect of the fluid viscosity on nondimensional whirl frequency: Water (엯), Shell 4113 oil (◻), Shell 13 oil (◇), Shell 37 oil (▿). (a) H=0.196 and (b) H=0.383.

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Figure 2

Imbalance response of empty rotor system: — for run-up, –엯–엯– for run-down

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Figure 3

Imbalance response of rotor system partially filled with water and Shell 37 oil: — for run-up, –엯–엯– for run-down. (a) With water. (b) With Shell 37 oil.

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Figure 4

Characteristics of rotor motion in run-up operation (with 280ml water, i.e., H=0.383). (a) Imbalance response, (b) waterfall diagram of vibration, and (c) motion orbit and corresponding spectrum.

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Figure 5

Effect of the fluid viscosity on the characteristics of the fluid-filled rotor, where 1, 2, 3, and 4 stand for water, Shell 4113 oil, Shell 13 oil, and Shell 37 oil, respectively; — for run-up, –엯–엯– for run-down. (a) H=0.069, (b) H=0.196, (c) H=0.383, and (d) H=0.502.

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Figure 6

The variation of the unstable speed region for different viscosity fluids. Run-up (엯, ◇), run-down (◻,◇). 1-water; 2-Shell 4113 oil; 3-Shell 13 oil; and 4-Shell 37 oil.

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