Magnetic-field analysis of ferrofluidic seals for optimum design

Abstract

Ferrofluidic devices have found applications in laser systems, high-vacuum equipment, computers, loudspeakers, inertia dampers, and motors. With the technique of magnetic-fluid sealing, one is called upon to produce custom solutions for complex and diverse seal problems, many of which may be characterized by very hostile environments, wide temperature ranges, and intense radioactive conditions. In designing a magnetic circuit for a magnetic-liquid seal, a number of factors, such as the size of the available envelope, pressure differential across the seal, chemical compatibility with various environments, and proper selection of permanent and soft magnetic materials need to be considered for achieving the most cost-effective solution while meeting the entire range of requirements for any specific application. In order to evaluate flux leakage and fringing while accounting for nonlinear characteristics of magnetic materials, it becomes necessary to resort to numerical techniques to determine the effect caused by varying the significant parameters and to achieve an optimized design for the device. This paper presents modeling techniques for simulating ferrofluidic seals, and methods to deal with various geometries including inherent symmetry. By numerically analyzing the model, detailed flux distribution plots have been obtained by means of a computer.