Research Papers: Hydrodynamic Lubrication

A Baseline Theory for the Design of Oil-Lubricated Centrally Pivoted Plane-Pad Thrust Bearings

[+] Author and Article Information
L. Chang

Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802

J. Tribol 132(4), 041703 (Oct 07, 2010) (6 pages) doi:10.1115/1.4002219 History: Received May 03, 2010; Revised July 15, 2010; Published October 07, 2010; Online October 07, 2010

A baseline theory is developed in this paper for the design of oil-lubricated centrally pivoted plane-pad thrust bearings. By focusing on the hydrodynamics generated by the viscosity-temperature effects of the lubricating oil, a mathematical model is derived with a single dimensionless parameter Wth. The nominal value of Wth is 0.1 for typical pad bearings in current industrial practice. The theory suggests two important design calculations for centrally pivoted plane-pad bearings: (1) The minimum oil film thickness in the bearing is about 0.65 of the film thickness determined using the classical isothermal lubrication theory with the pad pivoted at the maximum-load optimum location. Thus, by setting the film thickness to 1.54 times the design requirement, one may carry out design selections and calculations using the classical theory. (2) The friction in the bearing is about 1.7 times the value determined using the classical theory at the maximum-load optimum condition and with the film thickness equal to the design requirement. Thus, one may also use the classical theory to meaningfully calculate the friction and power loss in the centrally pivoted plane-pad bearing systems. The theory is developed based on fundamental lubrication science, order of magnitude analyses of the assumptions, and supporting evidence from numerical literature case studies. It would be a conservative baseline theory for the bearing design as other complicated and/or incidental mechanisms would help provide a design factor of safety.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

Schematic of a centrally pivoted plane-pad thrust bearing system (Fig. 17.1 (1))

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Figure 2

Schematic of a pivoted plane-pad bearing

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Figure 3

The one-to-one relation between the two model parameters

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Figure 4

Convergent inclination of the pad under practical design conditions

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Figure 5

Bearing load capacity associated with the viscosity-temperature effects

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Figure 6

Bearing film thickness illustrating ho≈0.65hmax under practical design conditions

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Figure 7

Bearing friction illustrating f≈1.7fiso under practical design conditions

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Figure 8

Friction results by Eq. 29 for comparison with results in Ref. 7



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