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TECHNICAL PAPERS

Entrainment and Inlet Suction: Two Mechanisms of Hydrodynamic Lubrication in Textured Bearings

[+] Author and Article Information
M. Fowell, A. V. Olver, A. D. Gosman

Department of Mechanical Engineering, Imperial College, London, UK

H. A. Spikes

Department of Mechanical Engineering, Imperial College, London, UKh.spikes@imperial.ac.uk

I. Pegg

 Duncton Technical Centre, Ford Motor Company, Laindon, Essex, UK

J. Tribol 129(2), 336-347 (Nov 11, 2006) (12 pages) doi:10.1115/1.2540089 History: Received July 28, 2006; Revised November 11, 2006

A new mechanism of hydrodynamic lubrication termed “inlet suction,” applicable to low convergence, micropocketed bearings, has been identified. In this, sliding of one of the bearing surfaces generates a subambient pressure in pockets close to the bearing inlet. Because this pressure is less than the external atmospheric pressure, lubricant is “sucked” into the bearing through the inlet land. This is quite a different mechanism from classical entrainment due to shear. In the current paper flow, hydrodynamic load support and friction are calculated using analytical solutions for simple pocketed bearings having a wide range of convergence ratios, including parallel surfaces. It is found that for the parallel case, inlet suction provides the only mechanism of hydrodynamic load support, and that inlet suction continues to play a major role in load support and friction reduction up to quite high convergence ratios. This mechanism of lubrication is believed to be responsible for the enhanced lubricant film formation and reduced friction of textured bearings, previously reported by a number of authors.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic diagram of parallel, pocketed bearing

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Figure 2

Dependence of load support on cavitation pressure for a pocketed, parallel bearing; a∕Bo=0.2, b∕Bo=0.3, ho=1μm, hd=5μm

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Figure 3

Pressure profiles across pocketed parallel bearing with cavitation, ho=1μm, hd=5μm; (a) with inlet land length a∕Bo=0.2, (b) with inlet land length a∕Bo=0.05

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Figure 4

Schematic diagram of convergent, pocketed bearing

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Figure 5

Schematic pressure profiles showing two types of fluid behavior in a pocketed bearing: (i) with cavitation; (ii) with no cavitation

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Figure 6

Influence of convergence ratio on load support for pocketed and nonpocketed bearings. For pocketed bearing a∕Bo=0.2, b∕Bo=0.3, ho=1μm, hd=5μm, pcav=0.

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Figure 7

Dependence of inlet suction flow and entrainment flow on convergence ratio for a cavitating, pocketed bearing; a∕Bo=0.2, b∕Bo=0.3, ho=1μm, hd=5μm, pcav=0

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Figure 8

Influence of convergence ratio on: (i) differential flow and (ii) load support, for a noncavitating pocketed and a nonpocketed bearing; a∕Bo=0.2, b∕Bo=0.3, ho=1μm, hd=5μm, pcav=0

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Figure 9

Piecewise linear approximation of converging film

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Figure 10

Influence of multiple pockets on load support for a pocketed parallel bearing; (i) two pockets of length 0.002m and (ii) eight pockets of length 0.0004m

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Figure 11

Influence of inlet length on load support for a parallel bearing at various pocket depths; b∕Bo=0.3, ho=1μm, pcav=0

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Figure 12

Plot of a∕Bo versus pocket depth for a pocketed parallel bearing with b∕Bo=0.3, ho=1μm, and pcav=0

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Figure 13

Influence of inlet length on load support for a convergent bearing at various pocket depths; b∕Bo=0.3, ho=1μm, pcav=0

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Figure 14

Effect of pocket on friction force for convergent bearing with b∕Bo=0.3, ho=1μm, pcav=0

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Figure 15

Effect of pocket on friction coefficient for convergent bearings with b∕Bo=0.3, ho=1μm, pcav=0

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Figure 16

Dependence of load support on minimum film thickness for parallel and convergent bearings: a∕Bo=0.2, b∕Bo=0.3, ho=1μm, hd=5μm

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