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Research Papers: Hydrodynamic Lubrication

Static 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, Niigata 940-2188, Japan
e-mail: s125012@stn.nagaokaut.ac.jp

Hiroo Taura

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

Satoru Kaneko

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

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received July 25, 2016; final manuscript received January 5, 2017; published online May 19, 2017. Assoc. Editor: Joichi Sugimura.

J. Tribol 139(5), 051703 (May 19, 2017) (11 pages) Paper No: TRIB-16-1233; doi: 10.1115/1.4035778 History: Received July 25, 2016; Revised January 05, 2017

Surface texturing is a technique for improving frictional and hydrodynamic performances of journal bearings because microtextures can serve as reservoirs for oil or traps for debris and may also generate hydrodynamic pressure. Over the past two decades, many researchers have experimentally demonstrated that texturing of various tribological elements can reduce friction force and wear, contributing to improvement of lubrication performance. Some numerical studies have examined the hydrodynamic lubrication conditions and reported that surface texturing affects the static characteristics of journal bearings, such as their load carrying capacity and friction torque. However, the validity of these numerical models has not been confirmed because of a lack of experimental studies. This study proposes a numerical model that includes both inertial effects and energy loss at the edges of dimples on the surface of a journal bearing in order to investigate the bearing's static characteristics. Experimental verification of journal bearings is also conducted with a uniform square-dimple pattern on their full-bearing surface. The results obtained by the model agree well with those of experiment, confirming the model's validity. These results show that under the same operating conditions, textured bearings yield a higher eccentricity ratio and lower attitude angle than the conventional ones with a smooth surface. This tendency becomes more marked for high Reynolds number operating conditions and for textured bearings with a large number of dimples.

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Figures

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Fig. 1

Analytical model with coordinate system

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Fig. 2

Schematic of experimental apparatus

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Fig. 3

Test bearing and loading equipment (cross-sectional view)

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Fig. 4

Schematic of square dimples

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Fig. 5

An overview of the photographs of textured surfaces: (a) TX1 (dimple width = 0.65 mm) and (b) TX2 (dimple width = 2.50 mm)

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Fig. 6

Loci of journal centers in TX1 and PLN for Re = 10

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Fig. 7

Relationships of eccentricity ratio ε and attitude angle φ to Sommerfeld number S for TX1 and PLN at Re = 10

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Fig. 8

Numerical results of pressure distribution at ε = 0.5: (a) pressure distribution at z¯  = 0.487 and (b) oil film region (p¯  > 0) for PLN (upper) and TX1 (lower)

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Fig. 9

Numerical results of circumferential mean velocity u¯θm for various values of Re; ε = 0.2 (θ − φ = 0 corresponds to maximum film-thickness position and θ − φ = π corresponds to minimum film-thickness position)

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Fig. 10

Loci of the journal centers of PLN and TX1 for different Re values

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Fig. 11

Relationships of eccentricity ratio ε and attitude angle φ to Sommerfeld number S for PLN and TX1 for various values of Re

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Fig. 12

Numerical results of the relationships of force components fε¯ and fθ¯ to ε for various values of Re: (a) reduction rates of force components fε¯ and fθ¯ for TX1 to corresponding ones for “PLN” and (b) ratio of tangential force component fθ¯ to radial force component fε¯ for PLN and TX1

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Fig. 13

Loci of the journal center of PLN, TX1 and TX2 for Re = 10

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Fig. 14

Relationships of eccentricity ratio ε and attitude angle φ to Sommerfeld number S for PLN, TX1 and TX2 for Re = 10

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Fig. 15

Numerical results of circumferential mean velocity u¯θm for different dimple patterns; ε = 0.2 (θ − φ = 0 corresponds to maximum film-thickness position and θ − φ = π corresponds to minimum film-thickness position)

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