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Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The objective of the study is to develop recommendations for accounting during the design stage and the feasibility of operating a magnetic fluid seal with a significant eccentricity of the rotating shaft relative to stationary pole attachments. This goal is achieved through conducted experi-mental research, the selection of necessary equations, boundary conditions, assumptions, and physical properties of the magnetic fluid when constructing a numerical mathematical model of the working gap of the magnetic fluid seal. The most important results of the study include ob-tained and analyzed distributions of the magnetic field, velocity field, and pressure in the mag-netic fluid, as well as the evaluation results of the impact of absolute and relative shaft misa-lignment in the magnetic fluid seal, centrifugal forces arising during shaft rotation, on the re-tained pressure drop by the seal. A significant reduction in the retained pressure drop occurs at an eccentricity of up to 40% of the working gap, and with further increases in eccentricity, the rate of pressure drop reduction slows down. The significance of the results lies in the potential utilization of the provided numerical model, as well as the outcomes of physical and mathemati-cal experiments, in the development of a magnetic fluid seal operating with significant misa-lignment between the rotating shaft and the housing. The dimensionless dependencies obtained allow for consideration, during the design stage, of the reduction in retained pressure drop with shaft eccentricity, taking into account the magnitude of the working gap, magnetic induction, and linear velocity.

Due to the complexity of working conditions and physical fields, the clearance flow field of the magnetic fluid sealing device for the main shaft of hydraulic turbine has always been a difficult point in the research of magnetic fluid seal. To study the flow characteristics of magnetic fluid in the clearance of the magnetic fluid sealing device for the main shaft of a hydraulic turbine, a numerical model of the flow field in the seal clearance of the main shaft was established and verified through experiments. The influence of the seal clearance, the width of the pole tooth, the height of the pole tooth and the width of the pole tooth slot on the flow of the magnetic fluid was studied by numerical calculation. The results show that the magnetic fluid near the pole tooth is not affected by the structural parameters and basically remains stationary. When the seal clearance is less than 0. 6 mm, the magnetic fluid in the clearance basically does not flow. When the seal clearance exceeds 0. 6 mm, the magnetic fluid near the pole slot and permanent magnet increases with the increase of the seal clearance, and the speed increases linearly. The flow of magnetic fluid near the pole tooth slot and permanent magnet decreases with the increase of the width of the pole tooth, and the velocity decreases linearly at first, decreases sharply at the width of the pole tooth from 3. 0 mm to 3. 5 mm, and finally tends to be stable. With the gradual increase of the height of the pole teeth and the width of the pole tooth slot, the magnetic fluid flow near the pole teeth and the permanent magnet will weaken. The magnetic fluid velocity near the pole teeth and slots will decrease sharply at the the height of the pole tooth from 1. 0 mm to 3. 5 mm and the width of the pole teeth from 3. 0 mm to 12 mm and finally become stable, while the magnetic fluid velocity near the permanent magnet has been decreasing linearly. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

When applied to seal liquid, magnetic fluid seal was prone to failure with the increase of shaft speed because of instability at the interface of these two fluids caused by shaft rotation. In order to avoid this problem, a new type of magnetic fluid seal was proposed, in which the magnetic fluid was separated from the sealed liquid by gas. The sealing principle of the structure was studied. Gas-liquid two-phase flow in the structure was simulated by computational fluid dynamics. A test rig of magnetic fluid seal with gas isolation was set up. Experiments of pressure resistance and seal durability of the original structure and structure with gas isolation for sealing water were carried out on the test bench. The results of theoretical analysis, CFD and experiments indicated that: there was no obvious relationship between shaft speed and performance of magnetic fluid seal when gas isolation was added for sealing water. Its pressure resistance was almost the same as that of the structure sealing gas. Its seal durability was significantly longer. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To find the relationship between the volume of ferrofluids injected into the sealing gap and the sealing pressure of magnetic fluid seal, a magnetic fluid sealing experimental equipment is well designed. The ferrofluids used in magnetic fluid seal experiments are expertly synthesized silicone oil based ferrofluids, which have a saturated magnetization as high as 31.4 kA/m. The finding of experiments and simulation results indicates that the sealing pressure has a positive relationship with the volume of ferrofluids when the volume is smaller than 0.5 mL. Based on those results, a theoretical model is established. The key factor affecting the sealing pressure is the thickness of liquid sealing barrier L , which is related to the volume of ferrofluids. [ABSTRACT FROM AUTHOR]

Herein, a divergent stepped magnetic fluid seal with a single magnetic source is designed to improve the pressure capability of ordinary magnetic fluid seal under small clearance. To explore the effects of injection volume, axial clearance, radial clearance, axial tooth number and radial tooth number on divergent stepped magnetic fluid seal, the pressure capability of magnetic fluid seal with an ordinary structure was comparatively analyzed through experimentation. According to the experimental results, there is no leakage or ejection of magnetic fluid from the sealing device when the critical pressure of divergent stepped magnetic fluid sealing is reached. The divergent stepped magnetic fluid seal structure performs better in pressure resistance the magnetic fluid seal with an ordinary structure. Also, the existence of axial teeth in the stepped magnetic fluid sealing structure leads to an increase in polar teeth, which not only extends the leakage path of the sealing medium but also exacerbates energy loss for the magnetic fluid carried by the sealed medium. This is effective in improving the pressure resistance of the magnetic fluid seal. When the axial tooth number reaches or exceeds the radial tooth number and the axial clearance falls below the radial clearance, the divergent stepped magnetic fluid seal with small clearance has a pressure capability that is 4.1–6 times higher than the critical pressure of ordinary magnetic fluid seal. When the axial clearance exceeds the radial clearance and the axial tooth number falls below the radial tooth number, the divergent stepped magnetic fluid seal has a critical pressure that is 1.9–3.6 times higher than that of conventional magnetic fluid seal. [ABSTRACT FROM AUTHOR]

When sealing liquids with magnetic fluid, the interfacial stability problem caused by the interaction between the magnetic fluid and the sealed liquid leads to poor sealing performance. Centrifugal force is generated by the rotation of the sealed liquid in the back blade seal, which forms back pressure to reduce the load of the seal or prevents the sealed liquid from leaking. To reduce the influence of the shaft speed on the sealing performance, a combined magnetic fluid and back blade seal was designed for sealing liquids and a combined seal experiment stand was set up. Theoretical and experimental studies were carried out. The results showed that under a higher shaft speed, the combined seal structure had better sealing performance in which the back blade seal played the main role; the magnetic fluid seal played a major role in stopping and lowering the speed to prevent seal leakage. The combined seal could run stably under different shaft speeds. [ABSTRACT FROM AUTHOR]

The operating conditions of magnetic fluid seals during reciprocating motion are so different from those observed in rotating motion that the use of their conventional structures for reciprocating motion seals yields no good results. The analysis of the sealing mechanism of magnetic fluid seals in reciprocating motion shows that the operation of these seals is affected by the carry-over phenomenon and magnetic fluid film deformation in the sealing gap, which depends on the velocity of the reciprocating motion. The reduced amount of magnetic fluid in the sealing gap caused by the reciprocating motion of the shaft is the main reason for seal failures. The paper presents a short characterisation of magnetic fluid sealing technology, the principle of sealing, the operation of the magnetic fluid and the seal failure mechanism in linear motion of the shaft. Moreover, some new structural designs of hybrid seals, being combinations of typical hydraulic seals with magnetic fluid seals for reciprocating motion, and some examples of magnetic fluid sealing structures for hydraulic cylinders and piston compressors which have practical application values are presented.

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Material properties of permanent magnet in the magnetic fluid seal are important factors that determine the sealing effect. However, the relationship between the magnetic properties of permanent magnet and the failure-pressure has not been studied quantitatively in the available research. In this work, the relationship between material properties of permanent magnet and the failure-pressure of magnetic fluid seal was obtained from theoretical analysis and numerical simulation. The permanent magnet was changed in materials to calculate the failure-pressures of a typical magnetic fluid seal. The results show that the failure pressure of the magnetic fluid seal increases with the increase of the maximum magnetic energy product of the permanent magnet, but there is a turning point. After that, the failure-pressure decreases as the maximum magnetic energy product increases.

Magnetic fluid seal(MFS) is one of the most mature applications of magnetic fluid(MF) and is widely used in numerous fields. When applying the MFS at − 55 ℃(the low temperature), it will lead to a high initial torque situation and a noticeable seal capacity reduction. This situation results in sealing failure and impedes the normal device startup. In this study, we synthesized MF based on polyalpha-olefins-3.5 (PAO-3.5), demonstrating fluidity at − 55 ℃, a saturated magnetization of 46.7 kA/m, and stability exceeding 2 months. The low pour point of PAO-3.5 based MF positions them as a good material choice for MFS applications in low temperature. And a structure of field-controlled MFS to control the magnetic field in sealing gap was proposed. To emphasis the necessity of the control of magnetic field, empirical equations were employed to model the viscosity and yield stress of MF under varying magnetic field strengths and temperatures, explaining the impacts of these factors. And the starting torque of MFS in specific conditions can be predicted. Notably, the use of field-controlled MFS have decreases in starting torque during non-pressure-resistant scenario, pressure-resistant scenario and long-term use. [ABSTRACT FROM AUTHOR]

In response to the requirement of high vacuum and leakage rate of a small-diameter low-speed device of an enterprise, a double magnet multistage magnetic fluid sealing device is designed by analyzing the advantages and disadvantages of four different vacuum magnetic fluid sealing devices. The Ansys simulation software is used to analyze and calculate the magnetic field strength and distribution of this magnetic fluid sealing device, discuss the influence of the number of intermediate section pole teeth and the seal gap size on the pressure resistance of the magnetic fluid seal, and summarize the law. The proposed structure of the double magnet multistage magnetic fluid sealing device is optimized and determined by the influence law of structural parameters. Compared with traditional sealing forms, the advantages of the sealing device proposed in this article can be summarized as low processing difficulty, good reliability, and high pressure resistance. The reliability and rationality of this magnetic fluid sealing device are demonstrated by Ansys simulation results, which provide a reference for the structural design and analysis of small-diameter low-speed vacuum magnetic fluid sealing devices.

A magnetic fluid seal is often used in complex working conditions with harsh environmental requirements. Timely and accurate identification of the seal status can help avoid the major economic losses and even casualties caused by the seal failure. However, research on the recognition of magnetic fluid seal status is still at the exploratory stage internationally. Aiming at the problem of inclusion of other components and Gaussian noise when using acoustic emission nondestructive testing technology to detect the magnetic fluid seal status, a new recognition method based on the combination of high-order cumulant image and VGG16 convolutional neural network is proposed to identify the magnetic fluid seal status in this paper. In this method, high-order cumulant images are used for the denoising and feature selecting of detected signals, and the VGG16 convolutional neural network is trained to automatically learn image features to classify and recognize high-order cumulant images representing different sealing states. Experiments show that the accuracy of image recognition using VGG16 is significantly higher than that of other methods. The VGG16 method can identify the magnetic fluid seal state accurately and effectively, with strong robustness and Gaussian noise suppression ability.

Magnetic fluid seal is a new type of sealing method, which has been applied in many fields. For some fields, such as aviation and aerospace, high sealing performance, large shaft diameter, and small design space are required, which brings difficulties to the sealing design. Therefore, it is necessary to study a large diameter magnetic fluid seal with thin-wall parts. In this article, the effects of seal clearance and shaft deflection on the magnetic field distribution of magnetic fluid seal are analyzed by the finite element method. At the same time, the force of seal shaft in the assembly process is also simulated. The influence of the amount of magnetic fluid on the pressure resistance is analyzed. The low-temperature starting torque and high-temperature pressure resistance of magnetic fluid seal are experimentally studied, and the optimal injection amount of magnetic fluid is obtained. The research content of this article can be used as a reference for the design of a large diameter magnetic fluid seal with thin-wall parts.

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The operating conditions of magnetic fluid seals during reciprocating motion are so different from those observed in rotating motion that the use of their conventional structures for reciprocating motion seals yields no good results. The analysis of the sealing mechanism of magnetic fluid seals in reciprocating motion shows that the operation of these seals is affected by the carry-over phenomenon and magnetic fluid film deformation in the sealing gap, which depends on the velocity of the reciprocating motion. The reduced amount of magnetic fluid in the sealing gap caused by the reciprocating motion of the shaft is the main reason for seal failures. The paper presents a short characterisation of magnetic fluid sealing technology, the principle of sealing, the operation of the magnetic fluid and the seal failure mechanism in linear motion of the shaft. Moreover, some new structural designs of hybrid seals, being combinations of typical hydraulic seals with magnetic fluid seals for reciprocating motion, and some examples of magnetic fluid sealing structures for hydraulic cylinders and piston compressors which have practical application values are presented. [ABSTRACT FROM AUTHOR]

When sealing liquids with magnetic fluid, the interfacial stability problem caused by the interaction between the magnetic fluid and the sealed liquid leads to poor sealing performance. Centrifugal force is generated by the rotation of the sealed liquid in the back blade seal, which forms back pressure to reduce the load of the seal or prevents the sealed liquid from leaking. To reduce the influence of the shaft speed on the sealing performance, a combined magnetic fluid and back blade seal was designed for sealing liquids and a combined seal experiment stand was set up. Theoretical and experimental studies were carried out. The results showed that under a higher shaft speed, the combined seal structure had better sealing performance in which the back blade seal played the main role; the magnetic fluid seal played a major role in stopping and lowering the speed to prevent seal leakage. The combined seal could run stably under different shaft speeds.

The advantages of magnetic fluid seals, such as low friction moment, high tightness, and high durability, have been known for many years. However, they are used particularly in air or vacuum environments and the application of this type of seal in water still remains a problem. This is mainly due to the friction occurring between the two fluids and interfacial instability. This publication focuses on investigating the influence of magnetic fluid properties on the mechanism of pressure transfer between sealing stages. The main aim was to better understand the leak mechanism in this type of seal and to be able to select ferrofluids (FFs) resistant to water for long-term operation after short-term testing. The tested seals rotated over 4.3 million times without failure. The results of the research carried out are recommendations for the selection of magnetic fluid, sealing stage width, and FF volume. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] • The research progress of magnetic fluid in vacuum, gas, liquid and dust prevention is reviewed. • The magnetic fluid component materials are introduced, including sealing characteristics, liquid–liquid interface stability, simulation analysis and structural design. • The future development in the field of magnetic fluid seals is envisioned. Magnetic fluids(MF) are stable colloidal solution systems consisting of a mixture of nanoscale magnetic particles, surfactants, and a base carrier fluid. Magnetic fluid sealing(MFS) technology has been widely used in gas and vacuum conditions, and research on liquid seals is also receiving increasing attention. Magnetic fluid seals have many advantages, such as "zero" leakage, green environmental protection, long service life, reliability and stability. The current review on the subject is limited to the form of magneto-fluidic applications, and there is no clear description of the specific structure and classification. In this paper, the research progress of magnetic fluid in the field of vacuum, gas, liquid and dust prevention is reviewed, and the magnetic fluid component materials are introduced in a categorized and summarized way, including sealing characteristics, liquid–liquid interface stability, simulation analysis and structural design. Finally, the future development in the field of magnetic fluid seals is envisioned. In the future, the magnetic fluid sealing technology is expected to further innovate and develop, bringing more breakthrough solutions to the sealing field. [ABSTRACT FROM AUTHOR]

The magnetic fluid seal is widely used in the high-speed mechanical devices. Also, the temperature of the seal increases with the viscous heating under the high shearing rate in the magnetic fluid. However, the influence of the temperature on the sealing performance has not been studied quantitatively in the available research. In this article, the change rule of magnetic fluid temperature and the influence on the sealing performance are researched through the simulation and experiment methods. The thermal field simulation is conducted with the heat generation in the fluid. To calculate the decrease of the magnetic properties quantitatively, the magnetization curves under different temperatures are measured to carry out the relationship between the saturation magnetization and temperature. Based on the magnetization curve result, the two-phase flow between air and magnetic fluid is solved under different shaft rotation speeds with the influence of temperature change. Besides, the sealing experiment is conducted with the highest rotation speed of 8000 rpm. The results of the simulation and experiment show good consistency, and the sealing capacity decreases with the rise of rotation speed. [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]

• The influence of temperature on the sealing performance of magnetic fluid is determined. • The magnetic field strength distribution under high temperature is obtained. • Optimization design on cooling structure of high-temperature magnetic fluid dynamic seal device is studied. In order to better sealing performance of magnetic fluid at high temperature, structural optimization design of cooling component in magnetic fluid dynamic sealing device at high temperature is studied in this paper. The magnetic field model of magnetic fluid sealing device at high-temperature is established to analyze the influence of temperature on the sealing performance of magnetic fluid, and magnetic field strength distribution is obtained. The simulated results show both magnetic induction strength difference and theoretical sealing pressure decrease gradually with the increase of the operating temperature. To reduce the temperature having great influence on sealing performance of magnetic fluid dynamic seal device, the temperature field model is constructed. Based on the Latin hypercube sampling method, the design matrix between cooling structural parameters and temperature is determined. In consideration of the neural network approach, the approximate agent model is built to analyze the correlation relationship between cooling structure parameters and cooling performance. The multi-island genetic algorithm is conducted on searching the optimal cooling structural parameters under global design space. The optimized results show that the average temperature of the permanent magnet is decreased by 27 °C, and the average temperature of the seal gap is reduced by 28 °C. The theoretical sealing differential pressure of the high-temperature magnetic fluid is improved by 49 KPa. [ABSTRACT FROM AUTHOR]

Magnetic fluid seal(MFS) is one of the most mature applications of magnetic fluid(MF) and is widely used in numerous fields. The permanent magnet is an integral component of the classic MFS and provides a stable and robust magnetic field. However, this leads to a high initial torque requirement and a noticeable separation between ferromagnetic particles and the base liquid in the presence of such a strong magnetic field. This situation results in starting difficulties and impedes the normal device startup, particularly in low-temperature environments. Moreover, a constant magnetic field fails to address fluctuating pressure. To address these issues, we have introduced a novel design for the field-controlled MFS. Through theoretical and finite element analyses(FEA), we derived the magnetic field distribution within the seal gap. Additionally, we established the theoretical range for the sealing capacity of the field-control MFS. Experimental results demonstrate that the magnetic field, sealing capacity, and starting torque all increase with higher coil currents. The reduction in starting torque is particularly pronounced at lower temperatures. By manipulating the magnetic field, the starting torque can be reduced by over 50%. The field-controlled MFS exhibits a 0.24 MPa sealing capacity without requiring cooling equipment, representing a 33% improvement in sealing capacity compared to the classic MFS without a coil. [ABSTRACT FROM AUTHOR]

Magnetic fluid seals are among the most common applications of ferrofluids. In such seals, the torque friction results only from the internal friction in the fluid and there is no direct contact between seal elements. Despite this, the heat generated during operation can be significant due to the low volume of the ferrofluid in the seal and high rotational speeds. The difficulty in calculating the torque friction is because the ferrofluid is a non-Newtonian fluid and changes its viscosity under the influence of a magnetic field. In order to measure torque friction in magnetic fluid seals, a special test stand was built. Tests were performed at different rotation speeds, different temperatures, and two seal stage geometries (rectangle and trapezoid). Numerical simulations were performed to determine the magnetic field distribution in the seal. Dynamic viscosity under the influence of the magnetic field was measured on a rotary rheometer. Mathematical models were compared with laboratory results. The results obtained from the calculations in some cases gave overstated values almost twice in value. An additional correction in the case of ferrofluid viscosity is proposed. [ABSTRACT FROM AUTHOR]

Rotational electron-beam mastering (REBM) systems have been studied with the aim of achieving the high data density necessary to facilitate the fabrication of next-generation optical data media, such as holographic storage. This study reports the design and testing of an ionic liquid (IL)-lubricated hydrostatic spindle system comprising an IL bearing, IL supply pump, and ionic magnetic fluid seal; and its outgassing performance under high-vacuum conditions. An inner vacuum chamber pressure of approximately 10−4 Pa was maintained during rotation of the spindle system. The outgassed products, as measured by a quadrupole mass spectrometer, were primarily generated from the air components in the lubricant IL. The non-repeatable runout in the radial direction, which is an important parameter of REBM accuracy, was 100 nm for a rotational speed of less than 130 min−1. The proposed method can be used for a 100-nm scale REBM device. • A high-vacuum-compatible hydrostatic spindle using ionic liquid was proposed. • The proposed spindle can rotate with high-accuracy and low outgassing in high-vacuum. • The outgassing from the spindle with ionic liquid circulation mechanism was investigated. • The usefulness of the spindle for an electron-beam lithography device was shown. [ABSTRACT FROM AUTHOR]

In this study, we developed an electromagnetically driven micropump with a magnetic fluid seal, which greatly contributes to the miniaturization of medical analytical sensor systems. The magnetic fluid seal applied to this micropump prevented the solution from entering the inside of the thrust bearing attached to the gap between the liquid feed rotor and the stator, and the abrasion powder generated from the bearing was prevented from being mixed into the solution. Furthermore, because the liquid feed rotor was rotated in a noncontact manner by the electromagnetic force from the coil attached to the external pump, continuous feeding of liquid with reduced pulsation was possible. When the rotational speed of the liquid feed rotor was 500 rotations per minute, the feed rate of pure water was 2 ml/min. At this rotational speed, there was no pure water intrusion into the thrust bearing nor separation of the magnetic fluid from the neodymium magnet. This result indicates that the magnetic fluid seal for the thrust bearing is effective. The micropump developed is a device that can be integrated with a biosensor chip, thereby contributing to the realization of a compact medical analysis sensor system that can be easily operated beside a patient. [ABSTRACT FROM AUTHOR]

Magnetic fluid (MF) seals have typically been used under various vacuum and gaseous low-pressure conditions. However, there are only a few cases in which MF seals can be used in a liquid environment. To promote this concept, a series of experimental tests was run in order to study the loading process among MF seals, as well as their self-repairing performance in aqueous environments. Exploring these factors has extended our knowledge of the sealing mechanisms in liquid environments. The results show that MF seals have enhanced self-repairing abilities in aqueous environments. [ABSTRACT FROM AUTHOR]

Abstract In this study, an ionic liquid (IL)-based magnetic fluid (MF) (IMF; IL-based MF) and dispersant was synthesized to create MF seals for rotational mechanisms in high-vacuum chambers, such as those in rotational electron beam mastering systems. The synthesized dispersant dispersed magnetite nanoparticles in pyridinium ionic liquid that is stable under magnetic fields. The outgassing from the IMF was investigated using a quadrupole mass spectrometer during a sliding test under high-vacuum conditions with a pressure of 10−6 Pa. The fragmentation pattern of the outgassing from the IMF was very similar to that of the base IL. Pollution-causing fragments were not detected under vacuum conditions on the order of 10−9 Pa. On the basis of our findings, we anticipate that the IMF is suitable for use in MF seals required in clean, high-vacuum conditions. Highlights • An ionic liquid-based magnetic fluid (IMF) using a new dispersant was synthesized. • The IMF generated low outgassing under friction in high-vacuum conditions. • Few fragments from the new dispersant were detected by Q-mass. • The usefulness of the IMF under high-vacuum conditions was shown. [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]

The magnetic fluid seal is one of the best known and widely used technical applications of magnetic fluid. However, the boundary and the flow regime with the rotation shaft cannot be observed by the experiment method. This paper presents a novel numerical simulation method to obtain the boundary and the velocity of the fluid in seals. The magnetic field of the seal is solved by the finite-element method, and the Navier–Stokes equations of the magnetic fluid based on the influence of magnetic force are solved by the finite-volume method. The two-phase flow is solved by the volume of fluid method. The seal capacities of the rectangle tooth and the trapezoid tooth with different rotation velocities are obtained. The result shows that the seal capacity decreases with the increase in the rotation velocity. [ABSTRACT FROM AUTHOR]

Magnetic fluid is a new type of functional materials. The seal of reciprocating shaft is a typical application of the magnetic fluid. However, there is little research on the magnetic fluid reciprocating seals, thus improving the sealing life and seal capacity is the key problem of studying the reciprocating seals. This paper presents a structure of the seal to test the sealing life and other characteristics. The magnetic field of the seal is estimated using the finite-element method. The thickness of the magnetic fluid on the surface of reciprocating shaft and the flow rate of magnetic fluid are obtained theoretically. The experimental result shows that the static seal capacity is related to the fluid volume. The static seal capacity obtained by experiment is approximately equal to the value through the simulation with sufficient magnetic fluid. The relationship between sealing life and the motion of the reciprocating shaft is obtained experimentally. The sealing life decreases rapidly with the increase of the stroke and velocity. [ABSTRACT FROM AUTHOR]

The sealing of large diameter rotating shaft in some special applications especially in aerospace and military industry needs to be sealed with magnetic fluids. However, the major problems of restricting the application of large diameter magnetic fluid rotary seal is the decrease of the pressure-resistance capacity of magnetic fluid seal at high temperatures and the bigger breakaway torque at low temperatures. To research effect of the temperature on the pressure-resistance capacity and breakaway torque of large diameter magnetic fluid seal, a sealing device with the diameter size of rotary shaft for 190 mm and the sealing gap for 0.1 mm was designed. Through the experimental test studied on the pressure-resistance capacity at −55 °C–70 °C and the breakaway torque at −55 °C–20 °C, exploring the influence rules of injection volumes of magnetic fluid and the standing time on the breakaway torque under at −55 °C. The experimental results show that the decrease of the saturation magnetization of magnetic fluid at high temperatures result in the pressure-resistance capacity falls, and the increase of the magnetic fluid viscosity at low temperatures is the key factors which causes the bigger breakaway torque. In theory, the analytical expression of between the viscous drag torque and the temperatures were derived, which could qualitatively explain the experimental rules of between the breakaway torque and the temperature at −55 °C–20 °C. In addition, the breakaway torque of magnetic fluid seal increases as the addition of the standing time and eventually becomes stable at −55 °C, and between the breakaway torque and the injection volumes of magnetic fluid showed a linearly change. [ABSTRACT FROM AUTHOR]

• Based on the requirements of the working conditions, a magnetic fluid seal device applicable to rotating shafts was designed in this study using magnetic field simulation analysis and experimental verification. • The relationships between several structural variables and seal pressure were analyzed, and the fitting curve and equation were derived via fitting analysis. • The magnetic field simulation results showed that sealing pressure decreased with an increase in the sealing gap, increased with the number of pole teeth, and increased and then decreased with an increase in the pole teeth angle. • The experimental results showed that the best sealing performance was achieved when the amount of magnetic fluid was 3 m L. • The sealing pressure significantly decreased with an increase in the rotational speed. Magnetic fluid seals are a new type of seal with zero leakage. Based on the requirements of the working conditions, a magnetic fluid seal device applicable to rotating shafts was designed in this study using magnetic field simulation analysis and experimental verification. The relationships between several structural variables and seal pressure were analyzed, and the fitting curve and equation were derived via fitting analysis. The magnetic field simulation results showed that sealing pressure decreased with an increase in the sealing gap, increased with the number of pole teeth, and increased and then decreased with an increase in the pole teeth angle. The trapezoidal pole teeth exhibited the best sealing performance. The experimental results showed that the best sealing performance was achieved when the amount of magnetic fluid was 3 m L. The sealing pressure significantly decreased with an increase in the rotational speed. [ABSTRACT FROM AUTHOR]

This study was carried out to develop a miniature magnetic fluid (MF) seal working in a liquid environment. The miniature MF seal is intended for use in a catheter blood pump. The requirements for the MF seal included a size of less than Ø4×4.5 mm, shaft diameter of 1 mm, sealing pressure of 200 mmHg, shaft speed of up to 40000 rpm, and life of one month. The miniature MF seal was composed of an NdFeB magnet (Ø4×Ø2×1) sandwiched between two pole pieces (Ø4×Ø1.1×0.5). A shield (Ø4×Ø1.2×1.5) was placed on the pole piece facing the liquid to minimize the influence of pump flow on the MF. The seal was installed on a Ø1 shaft. A seal was formed by injecting MF (Ms: 47.8 kA/m and η: 0.5 Pa·sec) into the gap between the pole pieces and the shaft. Total volume of the MF seal was 44 μL. A sealing pressure of 370 mmHg was obtained at motor speeds of 0-40,000 rpm. The seal remained perfect for 10 days in saline under the condition of a pump flow of 1.5 L/min (The test was terminated in accordance with plans). The seal remained intact after ethylene oxide sterilization during which the seal was exposed to high pressures. In conclusion, the newly developed MF seal will be useful for a catheter pump. [ABSTRACT FROM AUTHOR]

The influence of a temperature gradient and the Soret effect on the distribution of particles in a magnetic fluid seal (MFS) is studied. The heating of the MFS is found to be an effective method of homogenizing the magnetic fluid in the seal; in addition, the influence of the Soret effect on this process is found to be essential. [ABSTRACT FROM AUTHOR]