Research Papers: Hydrodynamic Lubrication

Stiffness and Damping Properties of (Semi) Floating Ring Bearing Using Magnetorheological Fluids as Lubricant

[+] Author and Article Information
Xiaohu Wang, Hongguang Li, Wen Lu, Guang Meng

State Key Laboratory of Mechanical System
and Vibration,
Shanghai Jiao Tong University,
Shanghai 200240, China

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received March 7, 2016; final manuscript received December 4, 2016; published online May 17, 2017. Assoc. Editor: Bugra Ertas.

J. Tribol 139(5), 051701 (May 17, 2017) (11 pages) Paper No: TRIB-16-1075; doi: 10.1115/1.4035773 History: Received March 07, 2016; Revised December 04, 2016

Magnetorheological fluids (MRFs) are applicable for achieving semi-active control in smart bearings. For hydrodynamic bearings lubricated with MRF, changes of the viscosity induced by magnetic field lead to changes of the dynamic characteristics such as stiffness and damping properties, providing the controllability to the bearings in rotor applications. Two main defects of the MRF, however, may potentially limit the use of this kind of bearings. One is that the magnetic field-induced viscosity alteration capability decreases as the shear rate increases; the other is the extra friction introduced by iron particles in the MRF in external magnetic field. In this study, the floating ring bearing (FRB) and semi-floating ring bearing (sFRB) are introduced to replace common journal bearing for MRF-lubricated smart bearings. Performance enhancement is achieved using FRB and sFRB. The lubrication behavior of MRF is studied using the Herschel–Bulkley (HB) model that incorporates the yield stress and the shear-thinning effect, which are the two main features of the MRF under shearing. A kind of MRF is developed for lubrication application, and a test rig is setup to measure its shear rate–stress relationship and then to identify its HB model parameters. With the identified HB model, stiffness and damping characteristics of the MRF-lubricated FRB and sFRB are studied. Results show that, compared to MRF-lubricated common journal bearings, the MRF-lubricated FRB and sFRB both achieve better performances in damping enhancement, while limiting the journal friction to a relatively lower degree.

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Fig. 1

Typical structures of a floating ring bearing and a semifloating ring bearing

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Fig. 2

Shear rate and stress relationship in a HB model

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Fig. 3

Lubrication oil film geometry

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Fig. 4

The geometry of the FRB (sFRB). Oj, Or and Ob are geometric centers of journal, floating ring, and bearing, respectively. φ1, φ2,e1, e2 are the four position parameters that determine the relative positions of Oj and Or to Ob. The ξObη coordinate system is defined by ξ pointing to the gravity direction. View A is the enlarged partial view of outer film formation velocities, and view B is the enlarged partial view of inner film formation velocities.

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Fig. 5

Numerical procedure of calculating FRB (sFRB) stiffness and damping coefficients

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Fig. 6

A sample of MRF using ISO VG32 and 9 μm carbonyl iron powder (30 wt.%)

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Fig. 7

Magnetorheological fluid shear property test system

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Fig. 8

The structure of the shear cell

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Fig. 9

The configuration of coils and shear cell

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Fig. 10

Coil–yoke magnetic field test system

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Fig. 11

Simulated and measured magnetic field in the coil–yoke system: (a) magnetic field in the gap of the shear cell and (b) simulated and tested magnetic field data comparison

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Fig. 12

Magnetic field in the coil–yoke system (I = 1.5 Å): (a) no drum and (b) drum installed

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Fig. 13

Identified HB model parameters trends with I and H. Trend lines are added for visual aid.

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Fig. 14

Shear rate–stress relationship of the tested MRF in magnetic field of Ma, Mb, Mc, and Md

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Fig. 15

Comparison of magnetic fields in outer and inner film for various excitation currents: (a) Ma magnetic field distribution in outer and inner film (I = 1.5 Å); and (b) comparison of inner and outer film magnetic fields for Ma, Mb, and Md (I = 0.8, 1.5, and 3.0 Å)

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Fig. 16

Ring rotation ratio ωr/ωj trends with outer eccentricity εo

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Fig. 17

Inner–outer eccentric ratio εi/εo trends with εo

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Fig. 18

Stiffness coefficients of inner and outer oil film of FRB relationship with εo: (a) direct stiffness in ξ direction kξξo and kξξi; (b) direct stiffness in η direction kηηo and kηηi; (c) cross stiffness kξηo and kξηi; and (d) cross stiffness kηξo and kηξi

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Fig. 19

Damping coefficients of inner and outer oil film of FRB relationship with εo: (a) direct damping in ξ direction cξξo and cξξi; (b) direct damping in η direction cηηo and cηηi; (c) cross damping cξηo and cξηi; and (d) cross damping cηξo and cηξi

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Fig. 20

Journal friction torque of the three studied types of bearings

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Fig. 21

Damping properties of the three studied types of bearings

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Fig. 22

Direct damping coefficients of the outer film of sFRB relationship with εo: (a) direct damping in ξ direction  cξξo and (b) direct damping in η direction cηηo




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