Parallel-surface thrust bearings at high speeds

Young, John (1961) Parallel-surface thrust bearings at high speeds. PhD thesis, University of Glasgow.

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Abstract

On a few occasions thrust bearings composed of two opposing flat parallel surfaces, have shown some indications of fluid film lubrication. This behaviour is in contradiction to the classical lubrication theory, which requires some geometrical restriction or 'taper wedge' effect in the bearing clearance in order to produce a load-carrying oil film. A tentative explanation by Fogg suggested a 'thermal wedge' effect in which the restriction to oil flow in the bearing is caused by thermal expansion of the fluid as it passes through a space of constant area. Theoretical analyses of the problem have confirmed the thermal wedge as a possible contributing factor in developing a load-bearing fluid film, but no direct correlation of theory with practice has previously been made. Towards this end, the theoretical analysis of the thermal wedge effect in a parallel surface bearing has been extended in this thesis to include the important effect of side leakage. General equations for temperature distribution, and for bearing pressure and load-carrying capacity for a sector pad have been developed, and from these were obtained characteristic equations which can be applied directly to an actual bearing, and which can be used to produce theoretical performance curves. A high-speed experimental apparatus was designed and built and tests were conducted on a parallel-surface thrust bearing, over a wide range of operating conditions. Readings of bearing friction, load, film thickness, oil flow and temperatures around the bearing were taken for a large number of tests. The maximum bearing pressure which could be carried without excessive friction and temperature rise was about 60 to 70 psi, which is in accordance with values for the old-fashioned horseshoe marine bearings. The experimental results were plotted and compared with the theoretical performance curves. Although a certain amount of scatter is evident in the experimental points, sufficient correlation is shown to confirm the thermal wedge behaviour, within the range of test conditions. It is concluded that the thermal wedge effect does exist and is of importance in a parallel surface bearing at high speeds and low loads. However, in order to produce a high load-carrying capacity, a parallel surface bearing of a type similar to the test bearing would be required to operate with a film thickness of about 0.0002 Inches and a temperature rise around the bearing pad of some 300

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: H L McBroom
Keywords: Mechanical engineering, Fluid mechanics
Date of Award: 1961
Depositing User: Enlighten Team
Unique ID: glathesis:1961-73148
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56
URI: http://theses.gla.ac.uk/id/eprint/73148

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