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Research Papers

The Oscillation Attenuation of an Accelerating Jeffcott Rotor Damped by Magnetorheological Dampers Affected by the Delayed Yielding Phenomenon in the Lubricating Oil

[+] Author and Article Information
Jaroslav Zapoměl

Institute of Thermomechanics,
The Czech Academy of Sciences,
Dolejškova 1402/5,
182 00 Praha 8,
Prague 182 00, Czech Republic;
Department of Applied Mechanics,
VSB-Technical University of Ostrava,
17. listopadu 15,
Ostrava 708 33, Czech Republic
e-mail: zapomel@it.cas.cz,
jaroslav.zapomel@vsb.cz

Petr Ferfecki

IT4Innovations National Supercomputing Center,
Department of Applied Mechanics,
VSB-Technical University of Ostrava,
Ostrava 708 33, Czech Republic
e-mail: petr.ferfecki@vsb.cz

1Corresponding author.

Contributed by the Technical Committee on Vibration and Sound of ASME for publication in the JOURNAL OF VIBRATION AND ACOUSTICS. Manuscript received March 3, 2017; final manuscript received July 17, 2017; published online September 29, 2017. Assoc. Editor: Patrick S. Keogh.

J. Vib. Acoust 140(1), 011017 (Sep 29, 2017) (10 pages) Paper No: VIB-17-1086; doi: 10.1115/1.4037512 History: Received March 03, 2017; Revised July 17, 2017

Adding damping devices to the rotor supports is a frequently used technological solution for reducing vibrations of rotating machines. To achieve their optimum performance, their damping effect must be adaptable to the current operating speed. This is offered by magnetorheological squeeze film dampers. The magnetorheological oils are liquids sensitive to magnetic induction and belong to the class of fluids with a yielding shear stress. Their response to the change of a magnetic field is not instantaneous, but it is a process called the delayed yielding. The developed mathematical model of the magnetorheological squeeze film damper is based on the assumptions of the classical theory of lubrication. The lubricant is represented by a bilinear material, the yielding shear stress of which depends on magnetic induction. The delayed yielding process is described by a convolution integral with an exponential kernel. The developed mathematical model of the damper was implemented in the computational procedures for transient analysis of rotors working at variable operating speed. The carried-out simulations showed that the delayed yielding effect could have a significant influence on performance of magnetorheological damping devices. The development of a novel mathematical model of a magnetorheological squeeze film damper, the representation of the magnetorheological oil by bilinear material, taking the delayed yielding phenomenon into consideration, increased numerical stability of the computational procedures for transient analysis of flexible rotors, and extension of knowledge on behavior of rotor systems damped by magnetorheological squeeze film dampers are the principal contributions of this paper.

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References

Figures

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Fig. 1

Scheme of a magnetorheological squeeze film damper: 1—outer ring, 2—inner ring, 3—magnetorheological oil, 4—electric coil, 5—squirrel cage spring, 6—damper housing, and 7—shaft

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Fig. 2

The cross section of the gap of a magnetorheological squeeze film damper

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Fig. 3

The introduced coordinate system

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Fig. 4

Scheme of the magnetic circuit

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Fig. 5

A scheme of the investigated rotor including the fixed coordinate system

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Fig. 6

Angular speed during the rotor deceleration

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Fig. 7

Displacement of the disk center in the horizontal (left) and vertical (right) directions

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Fig. 8

Displacement of the journal center in the horizontal (left) and vertical (right) directions

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Fig. 9

Transient orbits of the disk (left) and rotor journal (right) centers

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Fig. 10

Horizontal displacement of the disk center, 0.0/0.2 A, 200 rad/s, time constants 1 ms (left), 5 ms (right)

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Fig. 11

The disk center horizontal displacement, 0.2 A, 200/150 rad/s, time constants 1 ms (left), 5 ms (right)

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Fig. 12

The journal center horizontal displacement, 0.2 A, 200/150 rad/s, time constants 1 ms (left), 5 ms (right)

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Fig. 13

Orbits of the disk (left) and journal (right) centers, 0.2 A, 200 rad/s, time constants 1 ms, 5 ms

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Fig. 14

Orbits of the disk (left) and journal (right) centers, 0.2 A, 150 rad/s, time constants 1 ms, 5 ms

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Fig. 15

The disk (left) and journal (right) center vibration amplitude—time constant relationship, 0.2 A

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