Simulation of flow in a radial lip seal using different viscosity models

Abstract: Radial lip seals for rotating shaft have been used for a long time to keep lubricant within bearings and air and dust particles outside. How they work is not completely understood. This study examines operation of a plain radial lip seal lubricated with grease and aims at developing a model that explains the lubrication and sealing behaviour of this type of seal. One existing hypothesis how the seals function is the Weissenberg effect hypothesis. The hypothesis state that the lubricant is exposed to extreme shear load, which will contribute to the pumping effect and the maintenance of the lubricated film. An investigation is therefore made to examine if the non Newtonian characteristics of the grease prevents leakage. Comparison between Newtonian and non Newtonian fluid calculated by using the finite element software program COMSOL Multiphysics has been performed. The results show that there are differences between Newtonian and non Newtonian flow. The non Newtonian characteristics contribute to a larger flow in the axial direction as compared to the corresponding Newtonian fluid. This may contribute to a pumping effect and transportation of heat near the minimum film thickness. At the edge of the contact, the non Newtonian fluid becomes more viscous than the Newtonian fluid. The magnitude of the velocity in the pumping direction for the non Newtonian fluid decreases, which may contribute to the maintenance of the lubricated film.