A symmetric stepped magnetic fluid seal (SSMFS) structure with three magnetic sources is designed with the
goal of improving the leakage problem under the large clearance rotary seal condition. The magnetic field distribution
in the sealing clearance is analyzed using the finite element method when the radial and axial clearances
are both 0.4 mm. The pressure capacity is calculated, and the effects of the height of permanent magnets,
the length of the pole teeth, and the number of pole teeth are compared with those of diverging stepped magnetic
fluid seal (DSMFS) and converging stepped magnetic fluid seal (CSMFS) with three magnetic sources.
The numerical outcomes demonstrate that the SSMFS with three magnetic sources has a greater pressure
capacity than the other two seal structures. The effects of magnetic fluid injection volumes, radial and axial
clearances, various rotational speeds, and holding times are then investigated in tests to determine the pressure
capacity of the SSMFS with three magnetic sources. The results are compared to those of the other two structures.
The experimental date indicate that the SSMFS with three magnetic sources has a magnetic fluid injection
saturation of around 7 ml. The advantages of the SSMFS structure become more clear with the
modification of the radial clearance and axial clearance. With an increase in rotation speed and holding time,
the pressure capacity of SSMFS with three magnetic sources has no obvious change, but it is obviously higher
than that of the other two structures.