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COB266 O COMPORTAMENTO VISCO-ELÁSTICO DOS FLUIDOS LUBRIFICANTES NA ZONA DE VEDAÇÃO DE RETENTORES / THE VISCOELASTIC BEHAVIOUR OF LUBRICANT FLUIDS AT SEALING ZONE OF RADIAL LIP SEALS

Sylvio J. R. de Oliveira*, Volkert M. Wollesen**, Manfred Vötter**

* Departamento de Engenharia Mecânica, Escola de Engenharia - UFRJ - Caixa Postal 68503, CEP 21945-970, Rio de Janeiro, RJ, Brasil, E-Mail: sjro@serv.com.ufrj.br

** Arbeitsbereich Konstruktionstechnik II - TUHH - Denicke Str. 17, 21073, Hamburgo, Alemanha,

E-Mail: wollesen@tu-harburg.d400.de

The existing models that explain the lubricating and sealing mechanisms of radial lip seals consider behaviour of the fluid at sealing zone. Experimental results showed that the fluid supports very high shear rates (> ). At these conditions that fluid may deviate from newtonian behaviour and elastic properties might appear in the fluid. The non newtonian behaviour can explain why a lubricant film remains in the sealing zone of radial lip seals without leakage. This work presents a new hypothesis including a mathematical description in order to explain the lubricating and sealing mechanisms of radial lip seals.

Keywords: Radial Lip Seal, Non-Newtonian Fluid, Fluid Film Thickness, Pumping Mechanism

Retentor, Fluido Não-Newtoniano, Espessura de Filme, Mecanismo de Bombeamento

COB267 Sealing Zone Conditions of Radial Lip Seals Considering the Viscoelastic Properties of Lubricating Fluids

Kay Wiehler, Sylvio Jose Ribeiro de Oliveira & Manfred Vötter

Technische Universität Hamburg-Harburg, Konstruktionstechnik II, 21071 Hamburg, Germany, E-mail: wiehler@tu-harburg.de

The proceedings in the sealing zone between a lip seal and shaft surface are still not thoroughly understood. Due to the small fluid film thickness (micrometer range), the high temperatures (up to 200°C), the shear stress (MPa range) and the shear rate (> 10⁶ s^-1) it is difficult to achieve accurate measurements. A recently developed model takes the non-newtonian fluid behavior into account in order to describe the existence of a fluid film in the sealing zone. The radial pressure of the seal is compensated by the viscoelastic properties of the fluid and no deviation from parallel of the surfaces in micro and macro range is mandatory for this model. The measurement of rheological data of lubricating fluids at high shear rates is difficult and reliable data is hardly accessible. Therefore the data of higher viscous polymer melt and solution experiments is taken to model the viscoelastic behavior of lower viscous lubricating fluids. This simulation shows for various working conditions the influence of the fluid properties upon fluid film thickness, torque and pumping action of radial lip seals.

Keywords: Radial Lip Seal, Non-Newtonian Fluid, Pumping Mechanism, Fluid Film Thickness

COB342 NUMERICAL INVESTIGATION OF LAMINAR FLOW IN A FLAT WAVY CHANNEL

Jin Hu and Hans J. Leutheusser

Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada

A numerical approach is described which was developed to analyze experimental findings of flow passing between a sinusoidally wavy and a flat wall. The experimental data were obtained in a two dimensional wind tunnel, specially designed to simulate lubricant flow in a hydrodynamic bearing when the thickness of the fluid film approaches the order of magnitude of the size of the surface roughness. As such, the present investigation provides new insights into the physics of fluid film tribology.

Keywords: Finite Element Method; Laminar Flow; Lubrication; Roughness; Reynolds Equation.

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