Fundamental Research on a Radial Face Seal

Abstract

Radial face seals generally speaking operate under full hydrodynamic lubricating conditions, but the mechanism of lubrication is not completely understood. In a primarily experimental investigation the author has attempted to establish a description of the basic lubricating mechanism in radial face seals. The experimental apparatus and measuring techniques are briefly described. The experimental results display a high degree of reproducibility. Dynamic measurements of film thickness reveal fluctuations at twice shaft speed frequency that are concluded to be due to surface waviness. This conclusion is corroborated by the topography of the sealing faces. At constant geometry the friction coefficient and film thickness appear to depend on two dimensionless numbers incorporating average face pressure, sealing pressure, viscosity and speed. A simplified theory that lakes into account the macroroughness of the sealing faces shows close correlation with the experimental data obtained. Having obtained a strong indication that macroroughness of the sealing faces is the prime factor causing lubrication, a few practical consequences are discussed.