Upstream Pumping of Radial Lip Seals by Tangentially Deforming, Rough Seal Surfaces

Abstract

This paper aims at a theoretical explanation of the following two experimental observations of radial lip seals: fluid film formation and upstream pumping action. The origins of these observations are still poorly understood. A hydrodynamic analysis is presented for the fully flooded contact zone of a smooth shaft surface running against a rough seal surface. Four roughness structures are considered: one-dimensional sinusoidal and two-dimensional sinusoidal seal roughness structures both without and with a tangential seal surface displacement. The tangential seal surface displacement is chosen asymmetric with the axial position in the contact. It follows that the tangential deformation of the one- and two-dimensional seal roughness structures used in this paper can explain the aforementioned experimental observations and simulate the observed order of magnitude of load-carrying capacity, pump rate, and friction torque found in the literature.