Theoretical and Experimental Analysis of a Non Contacting Elastohydrodynamic Sealing

Abstract

This paper presents a novel elastohydrodynamic sealing concept for the contactless sealing of spool valves. The basic goal is that the spool and the sleeve can be manufactured with standard mechanical engineering precision. High initial gaps are compensated for the elastic deformation of an elastomer seal driven by a self-regulating hydrodynamic effect. The final gap reveals a small leakage within the range normal for precisely manufactured spool valves and also features a low friction since a direct, solid contact between the seal and the sleeve is prevented. This sought-after behavior in ideal conditions is compared with imperfect situations by means of a simulation study and experiments. The simulation uses a Finite Element model which takes the seal‘s elastic deformation, the mechanical contact, the sealing gap pressure and the surface roughness into account. A simple prototype of the sealing system was produced to test its functionality in real conditions. Leakages of QLeak <= 18 ml/min @180 bar were recorded. However, an unexpectedly high friction occurred indicating an actual contact between the seal and the sleeve. The component roughness was identified as the cause of this behavior.