Influence of gravity on the anti-pressure ability of magnetic fluid seal

Abstract

Magnetic fluid seal is the most important and mature application of magnetic fluid. Usually, gravity is ignored when analysing the performance of magnetic fluid seal and designing magnetic fluid sealing devices. With the expansion of magnetic fluid seal applications, gravity could seriously affect the performance of magnetic fluid seal, especially when the “O” ring diameter of magnetic fluid and sealing gap are both large. In this paper, the influence of gravity on the anti-pressure ability of magnetic fluid seal is theoretically analysed and proven by the experiments. The results show that magnetic fluid seal has a limit size that is directly proportional to the magnetic field gradient in the sealing gap and is inversely proportional to the ratio of magnetic fluid density to the magnetization. If the diameter of the magnetic fluid “O” rings, whose centre axis is perpendicular to the direction of gravity, is far smaller than the limit size, the influence of gravity on the anti-pressure ability of magnetic fluid seal can be neglected. However, if the size is close to or greater than the limit size, gravity would lead to a drop in the anti-pressure ability of magnetic fluid seal.