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To investigate the sealing mechanism and performance of the symmetric magnetic fluid seal (SMFS) with occlusal pole teeth (OPT), an experimental device was designed. The impact of magnetic fluid volumes and groove widths on the sealing mechanism and performance of the SMFS-OPT was investigated under different environments. Combining experimental results and numerical analyses, the applicability of the magnetic fluid sealing theoretical pressure resistance formula to SMFS-OPT is verified. The results show that low magnetic fluid volume and a large groove width prolong the differential pressure reduction process, thereby reducing the pressure resistance of the sealing device. Increasing the volume of the magnetic fluid increases the sealing device's self-healing rate but does not change the trend of the number of ruptures' impact on the pressure resistance. [ABSTRACT FROM AUTHOR]

To investigate the influence of temperature on the pressure transfer mechanism and failure mechanism for magnetic fluid seal (MFS) with opposite pole teeth (OPT), a sealing device with water circulation channel was designed. Sealing mechanism and performance of the sealing device at different temperatures were experimentally investigated under gas and vacuum environments, respectively, and comparison with the experimental results at normal temperature. Theoretical pressure resistance was calculated according to the theoretical pressure resistance formula for MFS with temperature coefficient. The results show that temperature affects the trend of pressure difference variation for the MFS-OPT. As temperature decreases, self-stability of the magnetic fluid film improves, while pressure resistance and self-healing capability of the MFS-OPT become more pronounced. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

To enhance the sealing pressure of normal ferrofluid seals with single magnetic source and small sealing clearance, a symmetrical ferrofluid seal (SFFS) was designed. The study utilizes a combination of finite element simulation and experiments to investigate the influence of crucial factors, including sealing clearance, number of pole teeth, step height, and pole teeth position, on the sealing pressure of SFFS. The findings indicate that the experimental sealing pressure values for SFFS closely match the theoretical sealing pressure values. The sealing pressure of the SFFS decreases as the sealing clearances and step height increase. It increases with an increase in the number of pole teeth. • A symmetrical ferrofluid seal with single magnetic source and small sealing clearance is designed. • Determine the maximum sealing pressure when the pole teeth are on the outer circular surface of the shaft and the end face of the pole piece. • This provides an important reference for the design and application of ferrofluid seal. [ABSTRACT FROM AUTHOR]

To investigate the failure mechanism of the magnetic fluid seal (MFS) with opposite pole teeth (OPT) in gas and vacuum environments, a sealing device was designed to directly observe the surface shape of the magnetic fluid film. The failure mechanism and sealing performance of the MFS-OPT in different environments were investigated and discussed with the ordinary MFS. Numerical analysis was conducted to study the magnetic field distribution of the sealing device. The self-healing ability of the MFS-OPT in different environments was investigated. The results indicate that the pressure transfer process of sealing device occurs in a step-by-step manner. When the sealing device fails, it will go through two consecutive stages of microleakage and complete leakage. On the other hand, when the ordinary MFS fails, it first goes through a bubble stage. The magnetic fluid in the sealing device leaks from the middle location of the opposing pole teeth. The sealing device exhibits higher pressure resistance in a gas environment than that in a vacuum environment. Both gas and vacuum environments have a higher pressure resistance for MFS-OPT compared to ordinary MFSs. • The MFS-OPT device can visualize the change of MF film shape. • In the MFS-OPT, the leakage channel occurs in the middle of the opposing PT. • In a gas environment, the gas bubbles are not produced by MF film during failure. • Pressure resistance and self-healing ability of the MFS-OPT are superior to the ordinary MFS. [ABSTRACT FROM AUTHOR]

To improve the pressure capability of ferrofluid seals with small clearance, a converging ferrofluid seal with double magnetic sources was designed. The magnetic field distribution in the clearances of the converging ferrofluid seal was studied by employing the finite-element method, and the theoretical pressure capability of the seal is calculated. The effects of ferrofluid injection volume, radial clearance, axial clearance, and the numbers of radial pole teeth and axial pole teeth on the pressure capabilities of converging ferrofluid seal device were investigated by experimental methods and compared with the experimental pressure capability of the stepless ferrofluid seal. The results show that the experimental and theoretical pressure capabilities of the converging ferrofluid seal are in good agreement. The saturated ferrofluid injection volume of the converging ferrofluid seal device is 1 mL. The experimental pressure capability of the converging ferrofluid seal does not decrease with increasing clearance or decreasing number of pole teeth. The pressure capability of the converging ferrofluid seal is related not only to the size of the clearance but also to the number of pole teeth. The pressure capability of the converging ferrofluid seal is better than that of the stepless ferrofluid seal. [ABSTRACT FROM AUTHOR]

In order to solve the problem of reciprocating seal for hydraulic cylinder, a new structure of Magnetorheological fluid (MRF) reciprocating seal with increasing width of pole teeth and pole piece was designed. The theoretical analysis of MRF reciprocating seal is carried out. The magnetic field intensity distribution in the sealing gap of MRF reciprocating seal was analyzed by finite element method. According to the pressure capability formula of MRF, the theoretical pressure capability is calculated. The influences of structure parameters such as the number of magnetic sources, sealing gap height, pole teeth length, the ratio of permanent magnet height to its length, the ratio of pole piece height to shaft radius on the sealing capabilities were studied. The results showed that the pressure capability of MRF reciprocating seal increases with the increase of the number of magnetic sources and with the decrease of the sealing gap height. With the increase of the pole tooth length, the pressure capability of the reciprocating seal increases. With the increase of the ratio of permanent magnet height to its length, the pressure capability of the reciprocating seal increases first and then decreases. With the increase of the ratio of the pole piece height to shaft radius, the pressure capability of the MRF reciprocating seal increases first and then decreases. [ABSTRACT FROM AUTHOR]

To reveal the pressure transfer and the failure mechanism of the convergent ferrofluid seal (CFFS) with staggered pole teeth (SPT), an experiment observation apparatus has been designed to direct monitoring of morphological transformations in the ferrofluid film. The pressure transfer and failure processes of CFFS-SPT during the pressurization process was investigated experimentally. The effects of eccentricity distance of axial pole teeth and magnetic isolation materials on pressure resistance of the seal were investigated. The results indicate that the pressure transfer in the radial chamber of CFFS-SPT is faster than that in the axial chamber. When seal fails, CFFS-SPT experiences micro-leakage and complete leakage stages. Moreover, the change in eccentricity distance of axial pole teeth does not affect the sealing mechanism. • A CFFS-SPT capable of observing changes in the surface shape of the FF film was designed. • There are two forms of CFFS-SPT failure, micro-leakage and complete leakage. • The pressure in radial chamber increases almost simultaneously, while the pressure in axial chamber increases incrementally. • The seal pressure resistance increases as the eccentricity distance of axial pole teeth increases. • This study provides important guidance for the development of FFS with high sealing performance. [ABSTRACT FROM AUTHOR]