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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.)

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 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.

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.)

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]

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]

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]

In vertical positioning systems, the friction force and the gravity load cause significant error. In order to minimize the effect of friction and gravity load, this paper presents the noncontact gravity compensator applying magnetic fluid seals. The structure of the magnetic fluid seals was proposed for the linear motion system, and the dimensions of the magnetic fluid seal components were determined based on the result of the magnetic field analysis using FEM. Magnetic field analysis was used in order to investigate the relationship between the seal capacity and varied dimensions. Based on the results of the analysis, several types of magnetic fluid seal units were manufactured, and the analytical results were compared with the results of the seal capacity evaluation experiment in order to confirm the validity of the magnetic field analysis. In addition, the gravity compensating system using the magnetic fluid seals was constructed and applied to a vertical positioning system. Positioning resolution was evaluated with stepwise positioning experiments. Tracking performance and the response of the pressure were evaluated by the continuous path control experiment. According to these experimental results, the effectiveness of the gravity compensator with magnetic fluid seal was confirmed.

It is proposed to replace regular electric motor output shaft seals with magnetic fluid seals, which ensure leak-tightness of upper bearing assemblies. A mathematical model that takes account of the interaction of magnetic and hydrodynamic processes in the seal gap is developed. The results of tests and operation of the magnetic fluid seals are reported. [ABSTRACT FROM AUTHOR]

Demands of ultra-precision machining systems have recently increased for machining three dimensional nano-geometries. Such systems require not only horizontal positioning systems but also vertical positioning systems with a nanometer positioning accuracy. However, the gravity load of moving mass negatively affects the positioning accuracy especially in a vertical positioning system. Therefore, it is necessary to compensate the influence of the gravity load for vertical ultra-precision positioning. Although the gravity compensation method using a non-contact vacuum cylinder has been proposed, it is difficult to improve the sealing performance of the non-contact seal. Thus, this study proposes the magnetic fluid seal for linear motion system with a gravity compensator. In general, magnetic fluid seals have been applied to rotary motion systems, however there are few studies on linear motion systems so far. When a magnetic fluid seal is applied to linear motion systems, the magnetic fluid leaks out of the seal clearance due to the movement, and it cannot keep the performance as a seal. In this study, it is possible to prevent leaking the magnetic fluid from the seal clearance and also to maintain the performance of the seal by holding a magnetic fluid by the two pole pieces shaped tapered tip and putting it near the piston made of non-magnetic material and coated with oil repellent layer. The proposed magnetic fluid seal performance has been evaluated. As a result, the result confirmed that the proposed magnetic fluid seal is useful as a linear motion seal, and the oil repellent layer on the piston surface can largely improve the sealing performance. [ABSTRACT FROM AUTHOR]

Abstract: A magnetic fluid (MF) seal enables mechanical contact-free rotation of the shaft and hence has excellent durability. The performance of a MF seal, however, has been reported to decrease in liquids. We have developed a MF seal that has a “shield” mechanism and a new MF with a higher magnetization of 47.9 kA/m. The sealing performance of the MF seal installed in a rotary blood pump was studied. The seal was perfect against a pressure of 150 mmHg in a continuous flow of 4.0 L/min for 275 days and against a pressure of 175 mmHg in a continuous flow of 3.9 L/min for 217 days. We have developed a MF seal that works in liquid against pressure mostly used clinically. The magnetic fluid seal is promising as a shaft seal for rotary blood pumps. [ABSTRACT FROM AUTHOR]

• Acidic and alkaline solution exhibited inhibitory effect against cavitation. • Acidic solutions have higher inhibitory effect than alkaline solutions. • The cavitation degree and flow length increased with higher deviation from pH = 7. • The cycle period reduced with higher offset value from pH = 7. • Acidic solutions should be used as reference for magneto-hydraulic sealing design. Owing to the different pH values of water resources in different places, it is not practical to design hydraulic–mechanical magneto-hydraulic sealing devices under clean water conditions. This study used a Venturi structure to analyze the relationship between the solution pH and cavitation. A high-speed camera and turbine flowmeter were used to record the primary cavitation flow rate, shedding period of the cavitation cloud, and flow direction length of the cavitation cloud of solutions with different pH values. The results showed that acidic and alkaline solutions can inhibit the occurrence of primary cavitation. Compared with clean water, acidic and alkaline solutions have longer cavitation cloud flow length, shortened cavitation cycle, and higher degree of cavitation. In detail, the degree of cavitation in the acidic solution is stronger than that in the alkaline solution. Therefore, the amplitude of the pressure pulsation in an acidic solution should be taken as the reference when designing a hydro-mechanical magneto-hydraulic sealing device. [ABSTRACT FROM AUTHOR]