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TECHNICAL PAPERS

Stability-Optimized Clearance Configuration of Fluid-Film Bearings

[+] Author and Article Information
Koichi Matsuda1

Department of Intelligent Machinery and Systems, Kyushu University, 744 Moto-oka, Fukuoka 819-0395, Japanmatsuda@mech.kyushu-u.ac.jp

Shinya Kijimoto, Yoichi Kanemitsu

Department of Intelligent Machinery and Systems, Kyushu University, 744 Moto-oka, Fukuoka 819-0395, Japan

1

Corresponding author.

J. Tribol 129(1), 106-111 (Aug 14, 2006) (6 pages) doi:10.1115/1.2401213 History: Received April 28, 2006; Revised August 14, 2006

The whirl instability occurs at higher rotating speeds for a full circular fluid-film journal bearing, and many types of clearance configuration have been proposed to solve this instability problem. A clearance configuration of fluid-film journal bearings is optimized in a sense of enhancing the stability of the full circular bearing at high rotational speeds. A performance index is chosen as the sum of the squared whirl-frequency ratios over a wide range of eccentricity ratios, and a Fourier series is used to represent an arbitrary clearance configuration of fluid-film bearings. An optimization problem is then formulated to find the Fourier coefficients to minimize the index. The designed bearing has a clearance configuration similar to that of an offset two-lobe bearing for smaller length-to-diameter ratios. It is shown that the designed bearing cannot destabilize the Jeffcott rotor at any high rotating speed for a wide range of eccentricity ratio. The load capacity of the designed bearings is nearly in the same magnitude as that of the full circular bearing for smaller length-to-diameter ratios. The whirl-frequency ratios of the designed bearing are very sensitive to truncating higher terms of the Fourier series for some eccentricity ratio. The designed bearings successfully enhance the stability of a full circular bearing and are free from the whirl instability.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Configuration of a fluid-film journal bearing

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Figure 2

Optimal clearance configuration of the designed bearings

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Figure 3

Squared values of the whirl-frequency ratios for the designed and circular bearings

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Figure 4

Dimensionless stiffness coefficients for the optimal and circular bearings

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Figure 5

Dimensionless damping coefficients for the optimal and circular bearings

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Figure 6

Dimensionless force as a function of eccentricity ratio for the optimal and circular bearings

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Figure 7

Friction coefficients as a function of Sommerfeld number for the optimal and circular bearings

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Figure 8

Typical pressure distribution for the designed bearing

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Figure 9

Truncation effect of the optimal Fourier coefficients on the whirl-frequency ratios

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