Radial Stiffness of a Ferrofluid Seal

This paper presents an analytical model for calculating the shape and the radial stiffness of ferrofluid seals used as radial bearings and this theoretical value of the radial stiffness is compared to measured values. This approach is interesting for the design of loudspeakers. Moreover, the concept of magnetic pressure is used to determine the seal shape as well as its energy. This paper corresponds to the case in which the ferrofluid seal is submitted to a high magnetic field. Furthermore, the calculation of the seal shape when the moving part is decentred is discussed. Indeed, the variation of the seal energy is evaluated with a three-dimensional analytical approach and both the restoring force exerted by the seal and the radial stiffness are calculated. The results obtained with an experimental setting confirm the validity of the model.