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Free-surface grease flow on a rotating plate
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.ORCID iD: 0000-0001-5294-1855
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.ORCID iD: 0000-0003-4785-7098
SKF Engineering & Research Center, Nieuwegein.ORCID iD: 0000-0001-9356-7599
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2014 (English)In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 56, no 2, p. 317-325Article in journal (Refereed) Published
Abstract [en]

Grease lubrication is traditionally used in a great variety of mechanical systems such as rolling bearings, seals, and gears where it has been shown more advantageous than oil, mainly due to its consistency allowing the grease to stay inside the system and not leak out. Knowledge of the flow dynamics of grease is important for the understanding and prediction of grease distribution for optimum lubrication and for the migration of wear and contaminant particles. Free-surface effects play an important role in rolling bearings and open gears as the configuration normally is filled with about 30 % grease to avoid heavy churning. In this study, an analytical model of the stationary uniform flow on a rotating disc is developed and validated with experiments. The model results in the velocity profile for the flow in the thin fully yielded viscous layer in connection to the surface as well as an expression for the plug flow region on top of the viscous layer. Furthermore, the depth-averaged velocity is derived as is the shear stress value on the plate. From the latter, follows a condition for the grease to start moving and in turn yielding an expression for the viscous layer thickness as a function of the grease yield stress value, grease density, angular velocity, and radial position. In addition, an expression of the layer thickness containing the ratio between the flow rate and the layer width which in turn can account for effects not included in the model such as wall slip and surface adhesion and thus add another degree of freedom into the model. Experiments with two different greases having NLGI grade 1 and 2, respectively, shows it is possible to obtain a good fit with the analytically obtained thickness using the rheological parameters for actual greases.

Place, publisher, year, edition, pages
2014. Vol. 56, no 2, p. 317-325
National Category
Fluid Mechanics and Acoustics Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Fluid Mechanics; Machine Elements
Identifiers
URN: urn:nbn:se:ltu:diva-15967DOI: 10.1007/s11249-014-0411-3ISI: 000344612900014Scopus ID: 2-s2.0-84925532980Local ID: f8d7807a-34ee-4614-8f55-56dda6554617OAI: oai:DiVA.org:ltu-15967DiVA, id: diva2:988943
Note
Validerad; 2014; 20140331 (lgwe)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved

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Westerberg, Lars-GöranLi, JinxiaHöglund, ErikLugt, PietBaart, Pieter

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Tribology letters
Fluid Mechanics and AcousticsTribology (Interacting Surfaces including Friction, Lubrication and Wear)

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