Abstract: To improve the pressure capability of magnetic fluid seal with a large gap, a new type of alternative combined magnetic fluid and labyrinth sealing structure is proposed on the basis of magnetic fluid seal with the multiple magnetic sources and a usual magnetic fluid sealing structure with two permanent magnets is designed. The pressure capabilities of the alternative combined seal with lubricating oil-based magnetic fluid, kerosene-based magnetic fluid and ester-based magnetic fluid under 0.3 mm to 0.7 mm sealing gap have been investigated by experimental methods. The magnetic field intensity is calculated by numerical method and the theoretical pressure capability of the magnetic fluid seal in the alternative combined seal is obtained according to the theoretical pressure formula of the magnetic fluid seal. The obtained experimental values of the combined seal have been compared and analyzed with the theoretical values of the magnetic fluid seal in the alternative combined seal. The results indicate that the alternative combined magnetic fluid and labyrinth seal shows good performance compared with the multiple magnetic sources and when the height of the sealing gap is larger than 0.4 mm, the pressure capability of the alternative combined seal decreases with the increase of the height of the sealing gap.

Key words: combined seal, labyrinth, large gap, magnetic fluid