Failure mechanism and pressure resistance investigation of divergent magnetic fluid seals with staggered pole teeth

This paper investigates the failure mechanism of a divergent magnetic fluid seal (MFS) with staggered pole teeth (SPT). By pole teeth, we mean the teeth machined on the inner ring surface of the pole pieces, which have a magnetic field gathering effect. A sealing apparatus capable of directly visualizing the surface deformation of the magnetic fluid film is developed, and the sealing mechanism is studied through experiments. The magnetic field distribution of the sealing apparatus is numerically analyzed to calculate its theoretical value, and this is compared against the experimental observations. The impacts of the eccentricity distance of the axial pole teeth and the addition of magnetic insulation materials on the pressure resistance of the MFS-SPT structure are investigated. The results show that, during the pressure loading process, the magnetic fluid moves to the low-pressure side. When the seal fails, micro-leakage and complete leakage occur successively in the MFS-SPT structure. There is good agreement between the experimental and theoretical pressure resistance of a divergent MFS-SPT. As the eccentricity distance of the axial pole teeth increases, the pressure resistance of the divergent MFS-SPT is enhanced. The sealing performance of the divergent MFS-SPT structure is improved when a magnetic insulation material is added to the grooves of the axial teeth.