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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 self-repairing performance of common ferrofluid seal (FS) and meet sealing requirements of long life under vacuum conditions, the interlaced FS device was developed. Effects of the number of axial pole teeth (PT), the number of radial PT, the width of the axial sealing gap (SG), and the height of the radial SG on their self-repairing performance were studied through experimental methods and compared with the self-repairing performance of the common FS. The results reveal that the self-repairing performance of interlaced FS is significantly better than that of the common FS with an increase in the number of FS ring ruptures. The ability to self-repairing of the interlaced FS diminishes or remains unchanged. As the quantity of axial PT increases, the self-repairing performance of interlaced FS is enhanced and then weakened. As the number of radial PT increases, the self-repairing performance of interlaced FS is weakened and then enhanced and then weakened. When the axial SG width exceeds 0.1 mm, the self-repairing performance of interlaced FS is weakened with the increase of SG. When the height of the radial SG exceeds 0.1 mm, the self-repairing performance of interlaced FS is weakened with the increase of SG. • The interlaced ferrofluid seal was designed. • The self-repairing performance of interlaced ferrofluid seals is much higher than that of common magnetic fluid seals. • The purpose of this study is to provide a reference for the design of vacuum seals that can withstand 1 atm. [ABSTRACT FROM AUTHOR]

To solve the problems of high leakage rate and short service life in vacuum equipment, a magnetic fluid reciprocating seal (MFRS) device was designed. A MFRS vacuum test bench was constructed for testing the leakage rate of seals. The effect of the magnetic fluid (MF) injection volume on the pressure resistance of the seals and the effects of reciprocating speed and reciprocating stroke on the leakage rate and the vacuum resistance of the seals were studied by experimental method. The results show that the optimum MF injection volume should be 2.5 ml, and the ratio of functioning MF injected to seal gap volume is 4.596. When the reciprocating shaft moves at a speed of less than 2.85 mm/s, the leakage rate varies in the order of 10−11 Pa m3/s. With the increase of the reciprocating speed, the vacuum of the sealing chamber first remains unchanged and then increases. With the increase of the reciprocating stroke, the vacuum of the sealing chamber first remains unchanged and then increases. The results of the study are of great significance for the design of reciprocating seals to meet the requirements of vacuum environment. • The magnetic fluid reciprocating sealing device is designed for vacuum equipment. • Design and construct the magnetic fluid reciprocating seal experimental bench for testing the leakage rate of seals. • The effects of reciprocating speed and reciprocating stroke on the leakage rate and vacuum tolerance of the seals were also experimentally investigated. [ABSTRACT FROM AUTHOR]

A novel symmetrical embedded magnetic fluid seal (SEMFS) structure was designed with the aim of enhancing the pressure resistance of the magnetic fluid (MF) seal with small gap under vacuum condition. The magnetic field distribution in the sealing gap (SG) was studied by numerical simulation, and the theoretical pressure resistant-withstanding of the SEMFS was obtained by combining the pressure resistance theories of stepped MFS. An experimental study was conducted to investigate the effects of magnetic fluid injection volume (MFIV), number of pole teeth, SG, and rotational speed of the rotating shaft on the seal's pressure resistance. The pressure resistant-withstanding values obtained were compared with those theoretically projected for the (SEMFS) and the ordinary magnetic fluid seal (OMFS), based on numerical analysis. The results indicate that the measured pressure value for the SEMFS matches well with the calculated pressure value. Furthermore, the SEMFS exhibits superior pressure resistance capabilities compared to the OMFS when subjected to the same parameters, which fully reflects the superiority of SEMFS structure. With an augment in the injection volume of MF, the pressure-withstanding performance of the SEMFS exhibits an initial upward trend followed by a gradual stabilization. Moreover, the pressure-withstanding performance of the SEMFS demonstrates a progressive enhancement with an increase in the number of radial pole teeth (RPT) and a corresponding increment in the number of axial pole teeth (APT). The ability to resist pressure of SEMFS decreases as the radial sealing gap (RSG) and axial sealing gap (ASG) increase. At low shaft speeds, the SEMFS's pressure resistance capability is not impacted by rotational speed and can be considered similar to a static seal. • A novel symmetrical embedded magnetic fluid seal structure was designed. • A sealing test bench was designed to conduct experimental studies on the sealing performance. • The symmetrical embedded magnetic fluid seal structure exhibits superior pressure resistance capabilities compared to the traditional sealing structure. • The increase of the magnetic fluid volume will cause the sealing pressure resistance to rise first and then stabilize. • The more the teeth, the smaller the seal gap and the greater the pressure value. The low speed has almost no effect on the pressure resistance. [ABSTRACT FROM AUTHOR]

To improve the sealing performance of ferrofluid, a Fe 3 O 4 magnetic nanoparticles with different coating times was synthesized by the chemical co-precipitation method, and the performance of diester-based Fe 3 O 4 ferrofluid was investigated and characterized. A convergent ferrofluid seal (CFFS) device was designed and the prepared ferrofluid was applied to it. The influence of important factors such as seal clearance and pole teeth of CFFS on the pressure capability of the CFFS are investigated using simulations and experiments. The results show that the prepared magnetization intensity of the ferrofluid is 29.5 kA/m. The simulation and experimental results of the CFFS agree well, and its performance is 3.3 times that of the ordinary ferrofluid seal. • The ferrofluid particles prepared by chemical precipitation method have uniform particle size and good anti-precipitation property. • The effect of radial and axial clearance size on the pressure resistance of the convergent ferrofluid seal was investigated. • The effect of the number of radial and axial pole teeth on the pressure resistance of the seal was investigated. • Designed convergent ferrofluid seal provides a theoretical basis for a convergent ferrofluid seal with high sealing performance. [ABSTRACT FROM AUTHOR]

To solve the problem of low pressure resistance of the conventional ferrofluid seal (FFS) under the condition of single magnetic source with large gap, which is difficult to meet the demand of vacuum sealing, the convergent FFS with stepped pole piece structure was designed. The designed structure is also compared with the conventional FFS structure. The effects of radial and axial sealing gaps (SGs), number of steps, step height on the pressure resistance and self-repairing ability of the seal were experimentally investigated. The results show that the new FFS structure can withstand 1 atm when the number of steps is 4 and the radial SG is 0.4 mm, which can provide a reference for vacuum sealing. The innovative FFS has a maximum pressure resistance 23 times higher than the conventional FFS for the same size. The self-repairing ability of the seal is negatively correlated with the radial and axial SG, the number of steps, and the height of the steps. The results of this study are important for the design of the FFS structure with single magnetic source that meets the requirements of a vacuum environment. • The ferrofluid seal with the stepped pole piece is designed. • The maximum pressure resistance of the new ferrofluid seal is 23 times higher than the conventional ferrofluid seal under the same size. • The purpose of this study is to provide a reference for the design of vacuum seals that can withstand 1 atm. [ABSTRACT FROM AUTHOR]

In order to enhance the pressure resistance of the ordinary magnetic fluid (MF) seal (MFS) with a large diameter shaft and large sealing gap, the converging embedded MFS (EMFS) device with a large diameter shaft and large sealing gap is designed in accordance with the principle of EMFS. A combination of numerical simulations and experimental studies is used to examine the effect of important factors such as the size of the sealing gap and the pole teeth (PT) number on the ability of the converging EMFS to pressure resistance. The findings indicate that the experimental pressure resistance of the converging EMFS with a large diameter shaft and large sealing gap is basically consistent with the theoretical pressure resistance. As the radial and axial sealing gaps increase, the pressure resistance of the converging EMFS decreases. With the increase of the number of radial PT, the pressure resistance of the converging EMFS first increases and then decreases. With the increase of the number of axial PT, the pressure resistance of the converging EMFS first increases, then decreases and then increases. The pressure resistance of the converging EMFS remains unchanged with the increase of the speed. • The converging embedded magnetic fluid sealing device with a large diameter shaft and large sealing gap is designed. • The effect of the size of sealing gap on the pressure resistance of the seal is studied. • The effect of the number of pole teeth on the pressure resistance of the seal is studied. • The designed sealing device has little effect on the pressure resistance of the seal at low speed. • This sealing device provides certain technical support for solving the problem of engineering machinery sealing. [ABSTRACT FROM AUTHOR]

Magnetic fluid seal (MFS) has been widely applied in the vacuum environment, but its pressure transfer mechanism has been less studied. This paper investigates the pressure transfer mechanism of MFS in the vacuum environment by designing an experimental device of MFS mechanism, which can observe the change of liquid film during the pressure transfer. Meanwhile, the pressure transfer mechanism of the designed device in the vacuum environment is compared with the that of MFS in the gas environment. The self-repairing performance of MFS in both vacuum and gas environments is investigated. Based on the MFS theory, the magnetic field distribution of the experimental device is analyzed numerically, and the theoretical pressure resistance is calculated and compared with the experimental value. The results show that the pressure transfer mechanism of MFS in the vacuum environment is similar to that in the gas environment with different forms. The pressure transfer form in the vacuum environment is magnetic fluid liquid film to produce a leakage channel. It is concluded that the self-repairing performance of MFS in the vacuum environment is better than that in the gas environment. • Using a comparative study approach. • The pressure transfer mechanism of MFS in the vacuum environment is similar to that in the gas environment. • The pressure transfer of MFS in the vacuum environment is the form of leakage channels generated in magnetic fluid film. • The self-repairing performance of MFS in the vacuum environment is better than that in the gas environment. [ABSTRACT FROM AUTHOR]