A design based on centrifugal inertia of rotational oil film for reducing pressure at shaft hole

Abstract

Shaft seal covers a very wide range of machinery and applications. Lip seals, which are used for sealing shafts against the exit or ingress of liquids, are a type of shaft seal. Reducing the wear of the sealing ring and extending its service life can increase the time interval for machine maintenance and inspection. In this paper, a disk structure for reducing the pressure difference between the inside and outside of the lip seals is proposed. The disk structure forms a layer of rotating oil film on the seal ring, so the oil pressure near the seal ring is less than in a sealing chamber. First, based on the similarity principle and the hypothesis of von Kármán, a theoretical model of the rotating oil film was established, and the dominant influence of inertia of circumferential velocity and viscosity of radial velocity on pressure distribution was expounded. Then, an experimental device that can measure pressure distribution and temperature was constructed, and a pressure distribution measurement experiment was conducted. Based on theoretical models and experiments, it was proved that the rotating disk could generate a pressure drop and the pressure drop was a function of the square of the rotating speed. The influence of temperature and oil film thickness was studied, and it was found that the increase in the temperature and oil film thickness weakened rotational flow inertia and enhanced radial flow viscosity, increasing pressure within the oil film. Additionally, it was observed that the oil in the sealing chamber produced a sunken liquid level due to the stirring of the rotating disk, which would reduce the boundary pressure at the periphery of the oil film and produce a greater pressure drop inside the oil film.