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Research Papers: Hydrodynamic Lubrication

Numerical and Experimental Analyses of the Dynamic Characteristics of Journal Bearings With Square Dimples

[+] Author and Article Information
Hiroyuki Yamada

Department of Energy and Environment Science,
Graduate School of Nagaoka
University of Technology,
Kamitomioka machi 1603-1,
Nagaoka-shi 940-2188, Niigata, Japan
e-mail: s125012@stn.nagaokaut.ac.jp

Hiroo Taura

Department of Mechanical Engineering,
Nagaoka University of Technology,
Kamitomioka-machi 1603-1,
Nagaoka-shi 940-2188, Niigata, Japan
e-mail: htaura@vos.nagaokaut.ac.jp

Satoru Kaneko

Department of Mechanical Engineering,
Nagaoka University of Technology,
Kamitomioka-machi 1603-1,
Nagaoka-shi 940-2188, Niigata, Japan
e-mail: kaneko@mech.nagaokaut.ac.jp

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received January 16, 2017; final manuscript received May 20, 2017; published online August 16, 2017. Assoc. Editor: Stephen Boedo.

J. Tribol 140(1), 011703 (Aug 16, 2017) (13 pages) Paper No: TRIB-17-1016; doi: 10.1115/1.4037151 History: Received January 16, 2017; Revised May 20, 2017

Numerous previous numerical studies have investigated the effect of surface texturing upon the static characteristics of journal bearings, including their load-carrying capacity and friction torque. In general, the dynamic characteristics of journal bearings are also important, since they are essential factors in predicting the vibration behavior of actual rotors supported by journal bearings. However, the effects of surface texture upon these dynamic characteristics have not been investigated through either numerical or experimental analysis. Thus, in the present study, such analyses were conducted to investigate the dynamic characteristics of textured journal bearings, such as their dynamic coefficients of oil film and the stability-threshold shaft speed supported by the bearings. Numerical analysis was done using a model that included inertial effects and energy loss; this model agreed well with experimental results concerning static characteristics from our previous study. Dynamic testing based on a sinusoidal-excitation method was also performed using textured journal bearings with uniform square dimples to verify the numerical results, which agreed qualitatively with those of experiment, confirming the validity of the numerical analysis. These results suggest that under the same operating conditions, the main effect of texturing upon the dynamic coefficients is to yield the cross-coupled stiffness coefficients with lower absolute values than the conventional ones with a smooth surface. The linear stability-threshold shaft speed of the rotor supported by the textured journal bearings became higher than that of a smooth bearing, mainly due to the reduction of cross-coupled stiffness coefficients. This tendency became more pronounced for high Reynolds number operating conditions and textured bearings with a large number of dimples.

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References

Figures

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Fig. 1

Analytical model of the journal bearing under dynamic state with a coordinate system

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Fig. 2

Schematic of a model rotor

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Fig. 3

Schematic of the experimental apparatus: ① test journal bearing, ② shaft, ③ rolling bearings, ④ electric motor, and ⑤ flexible coupling

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Fig. 4

Test bearing and loading equipment (cross-sectional view)

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Fig. 5

Schematic of the square dimples [21]

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Fig. 6

An overview of the images of the textured surfaces [21]: (a) TX1 (dimple width: 0.65 mm) and (b) TX2 (dimple width: 2.50 mm)

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Fig. 7

Relationship of stiffness coefficients to Sommerfeld number for TX1 and PLN at Re = 8: (a) direct terms and (b) cross-coupled terms

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Fig. 8

Relationship of damping coefficients to Sommerfeld number for TX1 and PLN at Re = 8: (a) direct terms and (b) cross-coupled terms

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Fig. 9

Tangential oil-film reaction force component under steady-state versus eccentricity ratio for TX1 and PLN at Re = 8

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Fig. 10

Relationship of linear stability-threshold shaft speed νc to Sommerfeld number S for TX1 and PLN at Re = 8

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Fig. 11

Relationship of stiffness coefficients to Sommerfeld number for PLN and TX1 for different Re values: (a) direct terms and (b) cross-coupled terms

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Fig. 12

Relationship of damping coefficients to Sommerfeld number for PLN and TX1 for different Re values: (a) direct terms and (b) cross-coupled terms

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Fig. 13

Relationship of linear stability-threshold shaft speed to Sommerfeld number for PLN and TX1 for different Re values

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Fig. 14

Relationship of stiffness coefficients to Sommerfeld number for PLN, TX1, and TX2 at Re = 8: (a) direct terms and (b) cross-coupled terms

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Fig. 15

Relationship of damping coefficients to Sommerfeld number for PLN, TX1, and TX2 at Re = 8: (a) direct terms and (b) cross-coupled terms

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Fig. 16

Relationship of linear stability-threshold shaft speed to Sommerfeld number for PLN, TX1, and TX2 at Re = 8

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