Pub Date : 2022-06-30DOI: 10.4283/jmag.2022.27.2.186
F. Ali, Fazli Haq, Naveed Khan, H. Alqahtani, Anees Imtiaz, I. Khan
This paper examines the magneto hydrodynamic two-phase blood (Casson fluid) flow in a vessel with heat conduction between blood and particles. The temperature of both phases is also considered. The model for the flow under consideration is formulated in terms of partial differential equations. Then the classical model is generalized by utilizing the Caputo fractional order derivative. The generalized equations are then non-dimensional-ized by using appropriate dimensionless variables. The exact dimensionless solutions are obtained via the joint application of Laplace & Hankel integral transforms. The influence of various embedded parameters on both the velocities (blood and magnetic particles) and the temperature distribution are presented graphically. It is worth noting that the particle and blood velocities decrease for increasing the values of magnetic parameter ( H ) which is useful to control the blood flow during magnetic therapy (for treating pain, such as the back, foot, or joint pain) and surgeries. It is worth noting that fractional model better describes the flow behavior than classical model by providing virous integral curves as shown in Fig.
{"title":"A Report of Generalized Blood Flow Model with Heat Conduction Between Blood and Particles","authors":"F. Ali, Fazli Haq, Naveed Khan, H. Alqahtani, Anees Imtiaz, I. Khan","doi":"10.4283/jmag.2022.27.2.186","DOIUrl":"https://doi.org/10.4283/jmag.2022.27.2.186","url":null,"abstract":"This paper examines the magneto hydrodynamic two-phase blood (Casson fluid) flow in a vessel with heat conduction between blood and particles. The temperature of both phases is also considered. The model for the flow under consideration is formulated in terms of partial differential equations. Then the classical model is generalized by utilizing the Caputo fractional order derivative. The generalized equations are then non-dimensional-ized by using appropriate dimensionless variables. The exact dimensionless solutions are obtained via the joint application of Laplace & Hankel integral transforms. The influence of various embedded parameters on both the velocities (blood and magnetic particles) and the temperature distribution are presented graphically. It is worth noting that the particle and blood velocities decrease for increasing the values of magnetic parameter ( H ) which is useful to control the blood flow during magnetic therapy (for treating pain, such as the back, foot, or joint pain) and surgeries. It is worth noting that fractional model better describes the flow behavior than classical model by providing virous integral curves as shown in Fig.","PeriodicalId":16147,"journal":{"name":"Journal of Magnetics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2022-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87703883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-06-30DOI: 10.4283/jmag.2022.27.2.217
Ji-Sung Jang, H. Lee, Seokhwan Yoon, Min-Cheol Jeon, S. Kim
This study aimed to assess the effect of zero-filling interpolation (ZIP) and various spatial resolutions on quality assurance (QA). Two important variables for the assessments of magnetic resonance image quality were included with recommended acceptance criteria: high-contrast spatial resolution and low-contrast object detectability with reference limits. All acquired data were divided into two groups: group A (without ZIP) and group B (with ZIP). The spatial resolutions of both images of T1-weighted and T2-weighted imaging in both directions fulfilled the American College of Radiology (ACR) criterion in group B. The observed high-contrast spatial resolution values were significantly different between the two groups up to a matrix size of 320 × 320 (p < 0.05). On the other hand, with a matrix size ≥ 384 × 384, no significant differences between the two groups were observed in terms of high-contrast spatial resolution (p > 0.05). For low-contrast object detectability, the total number of measured spokes in all groups fulfilled the ACR criterion. However, the low-contrast object detectability values without ZIP tended to decrease as the matrix size decreased. The use of ZIP can improve high-contrast spatial resolution and low-contrast object detectability while reducing image blurriness.
本研究旨在评估零填充插值(ZIP)和不同空间分辨率对质量保证(QA)的影响。评估磁共振图像质量的两个重要变量被纳入推荐的接受标准:高对比度空间分辨率和具有参考限的低对比度目标可检测性。所有获得的数据分为两组:A组(无ZIP)和B组(有ZIP)。b组t1加权和t2加权图像在两个方向上的空间分辨率均符合美国放射学会(American College of Radiology, ACR)标准，观察到的高对比度空间分辨率值在矩阵大小为320 × 320时，两组间差异有统计学意义(p < 0.05)。另一方面，当矩阵尺寸≥384 × 384时，两组在高对比度空间分辨率方面无显著差异(p > 0.05)。对于低对比度目标可检测性，所有组的测量辐条总数都满足ACR标准。而未加ZIP的低对比度目标可检测性值随着矩阵大小的减小而减小。ZIP的使用可以提高高对比度空间分辨率和低对比度目标的可检测性，同时降低图像的模糊度。
{"title":"Comparison of a Zero-filling Interpolation with a Real Matrix Size at 1.5 Tesla Based on Spin-echo Weighted Imaging with Various Spatial Resolutions: An ACR Phantom Study","authors":"Ji-Sung Jang, H. Lee, Seokhwan Yoon, Min-Cheol Jeon, S. Kim","doi":"10.4283/jmag.2022.27.2.217","DOIUrl":"https://doi.org/10.4283/jmag.2022.27.2.217","url":null,"abstract":"This study aimed to assess the effect of zero-filling interpolation (ZIP) and various spatial resolutions on quality assurance (QA). Two important variables for the assessments of magnetic resonance image quality were included with recommended acceptance criteria: high-contrast spatial resolution and low-contrast object detectability with reference limits. All acquired data were divided into two groups: group A (without ZIP) and group B (with ZIP). The spatial resolutions of both images of T1-weighted and T2-weighted imaging in both directions fulfilled the American College of Radiology (ACR) criterion in group B. The observed high-contrast spatial resolution values were significantly different between the two groups up to a matrix size of 320 × 320 (p < 0.05). On the other hand, with a matrix size ≥ 384 × 384, no significant differences between the two groups were observed in terms of high-contrast spatial resolution (p > 0.05). For low-contrast object detectability, the total number of measured spokes in all groups fulfilled the ACR criterion. However, the low-contrast object detectability values without ZIP tended to decrease as the matrix size decreased. The use of ZIP can improve high-contrast spatial resolution and low-contrast object detectability while reducing image blurriness.","PeriodicalId":16147,"journal":{"name":"Journal of Magnetics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2022-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84460644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-06-30DOI: 10.4283/jmag.2022.27.2.210
Gaeun Baek, Jun Lim, J. Yoon, Youngjin Lee
Among the representative types of magnetic resonance imaging (MRI) sequences, inversion recovery (IR) can improve the ability to detect brain lesions. The purpose of this study was to confirm the MRI characteristics according to TI changes in IR sequences. In this study, the MRiLab simulation program a newly developed, well-validated program was used to quantitatively analyze image characteristics with respect to the TI value in the IR sequence. Brain tissue phantom and standard phantom images were acquired by changing the TI at 100-ms intervals from 100 to 2,500 ms. In brain tissue phantom images, signal intensity (SI) values showed the lowest signals at TI values of 400, 700, and 2,500 ms in the white matter (WM), gray matter (GM), and cerebrospinal fluid (CSF), respectively. The contrast evaluated in CSF-WM was superior at 400 ms and the lowest at 1,800 ms. In addition, the contrast evaluated in WM-GM was superior at 400 ms and the lowest at 1,500 ms. In the case of the brain standard phantom, the SI and contrast showed the same tendency as brain tissue phantom. In conclusion, an appropriate TI value was derived for obtaining images with excellent SI and contrast between brain tissues using a newly developed simulation program.
{"title":"Performance Evaluation of MRI Based on Newly Developed MRiLab Simulation Using Inversion Recovery Pulse Sequence with Various Inversion Times","authors":"Gaeun Baek, Jun Lim, J. Yoon, Youngjin Lee","doi":"10.4283/jmag.2022.27.2.210","DOIUrl":"https://doi.org/10.4283/jmag.2022.27.2.210","url":null,"abstract":"Among the representative types of magnetic resonance imaging (MRI) sequences, inversion recovery (IR) can improve the ability to detect brain lesions. The purpose of this study was to confirm the MRI characteristics according to TI changes in IR sequences. In this study, the MRiLab simulation program a newly developed, well-validated program was used to quantitatively analyze image characteristics with respect to the TI value in the IR sequence. Brain tissue phantom and standard phantom images were acquired by changing the TI at 100-ms intervals from 100 to 2,500 ms. In brain tissue phantom images, signal intensity (SI) values showed the lowest signals at TI values of 400, 700, and 2,500 ms in the white matter (WM), gray matter (GM), and cerebrospinal fluid (CSF), respectively. The contrast evaluated in CSF-WM was superior at 400 ms and the lowest at 1,800 ms. In addition, the contrast evaluated in WM-GM was superior at 400 ms and the lowest at 1,500 ms. In the case of the brain standard phantom, the SI and contrast showed the same tendency as brain tissue phantom. In conclusion, an appropriate TI value was derived for obtaining images with excellent SI and contrast between brain tissues using a newly developed simulation program.","PeriodicalId":16147,"journal":{"name":"Journal of Magnetics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2022-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74992991","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-06-30DOI: 10.4283/jmag.2022.27.2.117
Taebong Noh, Hee-Ryoung Cha, Yang-Do Kim, Jung-Goo Lee
In order to fabricate high-coercivity hard magnetic RE-Fe-B powders from the waste bulk magnets, the hydrogen decrepitation (HD) and hydrogenation-disproportionation-desorption-recombination (HDDR) processes were employed to the waste RE-Fe-B magnets. The optimum HD and HDDR conditions for the waste RE-Fe-B magnets were established through the systematic investigation on the effect of HD and HDDR treatment temperature on the magnetic and microstructural properties of final recycled powders. We found that the waste magnets were crushed into the flakes with a uniform size distribution when the HD treatment was carried at 200 ℃. By applying the HDDR process to the HD treated flakes at 920 ℃, high coercivity of 11.2 kOe could be achieved in the recycled RE-Fe-B HDDR powders. Based on the results from the microstructural characteriza-tion, the underlying reasons for the magnetic and microstructural changes of the recycled powders as a function of the HD and HDDR treatment temperature is discussed in detail.
{"title":"High Coercive RE-Fe-B Powders Recycled via HD and HDDR Process from Waste Magnets","authors":"Taebong Noh, Hee-Ryoung Cha, Yang-Do Kim, Jung-Goo Lee","doi":"10.4283/jmag.2022.27.2.117","DOIUrl":"https://doi.org/10.4283/jmag.2022.27.2.117","url":null,"abstract":"In order to fabricate high-coercivity hard magnetic RE-Fe-B powders from the waste bulk magnets, the hydrogen decrepitation (HD) and hydrogenation-disproportionation-desorption-recombination (HDDR) processes were employed to the waste RE-Fe-B magnets. The optimum HD and HDDR conditions for the waste RE-Fe-B magnets were established through the systematic investigation on the effect of HD and HDDR treatment temperature on the magnetic and microstructural properties of final recycled powders. We found that the waste magnets were crushed into the flakes with a uniform size distribution when the HD treatment was carried at 200 ℃. By applying the HDDR process to the HD treated flakes at 920 ℃, high coercivity of 11.2 kOe could be achieved in the recycled RE-Fe-B HDDR powders. Based on the results from the microstructural characteriza-tion, the underlying reasons for the magnetic and microstructural changes of the recycled powders as a function of the HD and HDDR treatment temperature is discussed in detail.","PeriodicalId":16147,"journal":{"name":"Journal of Magnetics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2022-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77663216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-06-30DOI: 10.4283/jmag.2022.27.2.155
Xiaoqiang Yu, Lei He, Yuting Hu, Jiajie Li, Xiao Liu, Yuhan Wang, Chunji Li, Munan Yang, Z. Zhong
Cerium-containing (Ce) rare earth magnets with extraordinary cost-effectiveness are widely investigated around the world. However, when the concentration of Ce is much more, the kind of these magnets exhibits very poor thermal stability and overall magnetic properties. To weaken these disadvantages, we take eutectic Y 50 Ce 50 co-substitution alloys into account in this work. Magnetic properties, microstructures and metallurgical behaviors of (Y, Ce, Nd)-Fe-B magnets are systematically researched. For (Y 50 Ce 50 ) 10 Nd 20 Fe 68.9 B 1.1 SPSed permanent magnets, good overall magnetic properties are H cj = 725 kA/m, J r = 0.73 T and ( BH ) max = 81 kJ/m 3 . It schematically depicts that coarse grain zones and fine grain zones occur during the spark plasma sintering (SPS) process. With the Nd content increasing, the deleterious CeFe 2 phases disappear. In addition, the volume fraction and width of coarse grain zones decrease. Ce-rich and Ce-lean regions are also observed in main phases, while Y and Nd elements are uniformly distributed. TEM results show that Nd and Ce are rich in the grain boundary and Y elements prefer to enter in 2:14:1 main phases. This work is favorable to a balanced utilization of high abundance rare earth elements in Nd-Fe-B magnets.
具有极高成本效益的含铈稀土磁体在世界范围内得到了广泛的研究。然而，当Ce浓度过高时，这种磁体表现出非常差的热稳定性和整体磁性能。为了消除这些缺点，我们在这项工作中考虑了共晶y50 ce50共取代合金。系统地研究了(Y, Ce, Nd)-Fe-B磁体的磁性能、显微组织和冶金行为。对于(Y 50 Ce 50) 10 Nd 20 Fe 68.9 B 1.1 SPSed永磁体，其总体磁性能为hcj = 725 kA/m, jr = 0.73 T， (BH) max = 81 kJ/m 3。简要描述了放电等离子烧结(SPS)过程中出现的粗晶粒区和细晶粒区。随着Nd含量的增加，有害的cefe2相消失。粗粒带的体积分数和宽度减小。主相中有富铈区和贫铈区，Y和Nd元素分布均匀。TEM结果表明，Nd和Ce在晶界富集，Y元素倾向于以2:14:1主相进入;这一工作有利于钕铁硼磁体中高丰度稀土元素的平衡利用。
{"title":"Effects of Yttrium and Cerium co-substitution on Structures and Magnetic Properties of Nanocrystalline Nd-Fe-B Magnets","authors":"Xiaoqiang Yu, Lei He, Yuting Hu, Jiajie Li, Xiao Liu, Yuhan Wang, Chunji Li, Munan Yang, Z. Zhong","doi":"10.4283/jmag.2022.27.2.155","DOIUrl":"https://doi.org/10.4283/jmag.2022.27.2.155","url":null,"abstract":"Cerium-containing (Ce) rare earth magnets with extraordinary cost-effectiveness are widely investigated around the world. However, when the concentration of Ce is much more, the kind of these magnets exhibits very poor thermal stability and overall magnetic properties. To weaken these disadvantages, we take eutectic Y 50 Ce 50 co-substitution alloys into account in this work. Magnetic properties, microstructures and metallurgical behaviors of (Y, Ce, Nd)-Fe-B magnets are systematically researched. For (Y 50 Ce 50 ) 10 Nd 20 Fe 68.9 B 1.1 SPSed permanent magnets, good overall magnetic properties are H cj = 725 kA/m, J r = 0.73 T and ( BH ) max = 81 kJ/m 3 . It schematically depicts that coarse grain zones and fine grain zones occur during the spark plasma sintering (SPS) process. With the Nd content increasing, the deleterious CeFe 2 phases disappear. In addition, the volume fraction and width of coarse grain zones decrease. Ce-rich and Ce-lean regions are also observed in main phases, while Y and Nd elements are uniformly distributed. TEM results show that Nd and Ce are rich in the grain boundary and Y elements prefer to enter in 2:14:1 main phases. This work is favorable to a balanced utilization of high abundance rare earth elements in Nd-Fe-B magnets.","PeriodicalId":16147,"journal":{"name":"Journal of Magnetics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2022-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81904256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-06-30DOI: 10.4283/jmag.2022.27.2.141
T. Satiramatekul, Varunya Attasena, F. Bouillault
Numerical modeling by using the finite element method is developed for the prediction of magnetization. In this work, we modeled a superconducting strand made up of seven coupled filaments. We studied the influence of the deformation of the filaments on magnetization. We also studied the effect of the direction of the applied magnetic field on magnetization. We could calculate the magnetization of coupled superconducting filaments. We could also add the dependence of the current density according to the magnetic induction. We found that in the case where superconducting filaments are coupled, for a given spacing and whatever the direction of the applied magnetic field, the total magnetization of the strand does not depend on the deformation of the filaments in the strand if this strand is made up of several filaments.
{"title":"Effect of Direction of Applied Magnetic Field on Magnetization of Coupled Superconducting Filaments","authors":"T. Satiramatekul, Varunya Attasena, F. Bouillault","doi":"10.4283/jmag.2022.27.2.141","DOIUrl":"https://doi.org/10.4283/jmag.2022.27.2.141","url":null,"abstract":"Numerical modeling by using the finite element method is developed for the prediction of magnetization. In this work, we modeled a superconducting strand made up of seven coupled filaments. We studied the influence of the deformation of the filaments on magnetization. We also studied the effect of the direction of the applied magnetic field on magnetization. We could calculate the magnetization of coupled superconducting filaments. We could also add the dependence of the current density according to the magnetic induction. We found that in the case where superconducting filaments are coupled, for a given spacing and whatever the direction of the applied magnetic field, the total magnetization of the strand does not depend on the deformation of the filaments in the strand if this strand is made up of several filaments.","PeriodicalId":16147,"journal":{"name":"Journal of Magnetics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2022-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82648380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-31DOI: 10.4283/jmag.2022.27.1.056
Jiawei Liu, Decai Li
Magnetic fluid seal is one of the most mature applications of magnetic fluid. When the shaft has a large radial runout, the classical pole piece is easily damaged. Due to its small size, the commonly used pole piece structure harbors problems like poor seal performance under a large gap and poor processability. By exploring the distribution law of the magnetic field on the magnet’s surface, we provided theoretical support for the magnetic fluid seal using axially-magnetized ring magnets. New structures for the magnetic fluid seal using axially-mag-netized slotted ring magnets and the magnetic fluid seal using radially-magnetized ring magnets were proposed. Then, comparisons were made between the classical magnetic fluid seal and the magnetic fluid seal using ring magnets. The results revealed that the magnetic fluid seal using axially-magnetized slotted ring magnets and the magnetic fluid seal using radially-magnetized ring magnets exhibited a certain seal capacity, which could replace the classical magnetic fluid seal structure.
{"title":"Analysis on Seal Capacity of Magnetic Fluid Seal Using Ring Magnet","authors":"Jiawei Liu, Decai Li","doi":"10.4283/jmag.2022.27.1.056","DOIUrl":"https://doi.org/10.4283/jmag.2022.27.1.056","url":null,"abstract":"Magnetic fluid seal is one of the most mature applications of magnetic fluid. When the shaft has a large radial runout, the classical pole piece is easily damaged. Due to its small size, the commonly used pole piece structure harbors problems like poor seal performance under a large gap and poor processability. By exploring the distribution law of the magnetic field on the magnet’s surface, we provided theoretical support for the magnetic fluid seal using axially-magnetized ring magnets. New structures for the magnetic fluid seal using axially-mag-netized slotted ring magnets and the magnetic fluid seal using radially-magnetized ring magnets were proposed. Then, comparisons were made between the classical magnetic fluid seal and the magnetic fluid seal using ring magnets. The results revealed that the magnetic fluid seal using axially-magnetized slotted ring magnets and the magnetic fluid seal using radially-magnetized ring magnets exhibited a certain seal capacity, which could replace the classical magnetic fluid seal structure.","PeriodicalId":16147,"journal":{"name":"Journal of Magnetics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2022-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91266028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-31DOI: 10.4283/jmag.2022.27.1.079
Fang Yuan, Siqi Wang, Decai Li, Long Che
Considering various unstable factors when the large-diameter spindle operates at a high speed, such as eccentricity, centrifugal force, etc., the ordinary ferrofluid seal structures will show poor sealing performance. This paper proposes an axial-radial bidirectional ferrofluid seal structure with radial oblique teeth to improve the sealing performance. The pressure resistance of the radial ferrofluid seal structure in the magnetic circuit is theoretically analyzed. The magnetic flux distribution characteristic in the gap of the oblique teeth is studied by magnetic field simulation. According to the analysis results of the magnetic induction intensity, to obtain the larger theoretical pressure resistance, the optimal angle of oblique teeth is 77.87°, 64.28° and 62.81° under the radial seal structure with different gaps of 0.1 mm, 0.15 mm and 0.2 mm, respectively. In addition, simulation analysis is carried out to obtain the fluid pressure and velocity distribution of the radial ferrofluid seal structure with different oblique teeth angles. When the oblique teeth angle is small, the pressure drops and gas flow speeds in the ferrofluid area are all lower, and the pressure resistance is higher.
{"title":"Sealing Behavior Research on the Radial Ferrofluid Seal Structure with Oblique Teeth","authors":"Fang Yuan, Siqi Wang, Decai Li, Long Che","doi":"10.4283/jmag.2022.27.1.079","DOIUrl":"https://doi.org/10.4283/jmag.2022.27.1.079","url":null,"abstract":"Considering various unstable factors when the large-diameter spindle operates at a high speed, such as eccentricity, centrifugal force, etc., the ordinary ferrofluid seal structures will show poor sealing performance. This paper proposes an axial-radial bidirectional ferrofluid seal structure with radial oblique teeth to improve the sealing performance. The pressure resistance of the radial ferrofluid seal structure in the magnetic circuit is theoretically analyzed. The magnetic flux distribution characteristic in the gap of the oblique teeth is studied by magnetic field simulation. According to the analysis results of the magnetic induction intensity, to obtain the larger theoretical pressure resistance, the optimal angle of oblique teeth is 77.87°, 64.28° and 62.81° under the radial seal structure with different gaps of 0.1 mm, 0.15 mm and 0.2 mm, respectively. In addition, simulation analysis is carried out to obtain the fluid pressure and velocity distribution of the radial ferrofluid seal structure with different oblique teeth angles. When the oblique teeth angle is small, the pressure drops and gas flow speeds in the ferrofluid area are all lower, and the pressure resistance is higher.","PeriodicalId":16147,"journal":{"name":"Journal of Magnetics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2022-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83498770","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-31DOI: 10.4283/jmag.2022.27.1.051
Eui-Jong Park, Yong-Jae Kim
The power transmission of magnetic gears, based upon the at-tractive force of magnets, does not involve direct contact between the power transmission shafts. Thus, vibration or noise, due to friction, can be reduced. How-ever, magnets and iron cores, which are the main components of magnetic gears, generate cogging torque. This increases torque ripples that are the cause of the noise and vibration of permanent-magnet (PM) machines. In this study, a torque ripple reduction method, using the combination of number of poles and number of pole pieces was proposed. This method uses the structural characteristics of magnetic gears only. This method was suggested instead of the existing torque ripple reduction methods for PM machines to reduce the torque ripples of magnetic gears. Furthermore, the correlation between the numbers of poles, pole pieces, and torque ripples was analyzed. From this analysis, a design guideline that minimizes torque ripples in the initial design of magnetic gears was proposed.
{"title":"Torque Ripple according to The Number of Permanent Magnet Poles of Magnetic Gear","authors":"Eui-Jong Park, Yong-Jae Kim","doi":"10.4283/jmag.2022.27.1.051","DOIUrl":"https://doi.org/10.4283/jmag.2022.27.1.051","url":null,"abstract":"The power transmission of magnetic gears, based upon the at-tractive force of magnets, does not involve direct contact between the power transmission shafts. Thus, vibration or noise, due to friction, can be reduced. How-ever, magnets and iron cores, which are the main components of magnetic gears, generate cogging torque. This increases torque ripples that are the cause of the noise and vibration of permanent-magnet (PM) machines. In this study, a torque ripple reduction method, using the combination of number of poles and number of pole pieces was proposed. This method uses the structural characteristics of magnetic gears only. This method was suggested instead of the existing torque ripple reduction methods for PM machines to reduce the torque ripples of magnetic gears. Furthermore, the correlation between the numbers of poles, pole pieces, and torque ripples was analyzed. From this analysis, a design guideline that minimizes torque ripples in the initial design of magnetic gears was proposed.","PeriodicalId":16147,"journal":{"name":"Journal of Magnetics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2022-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87458512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-31DOI: 10.4283/jmag.2022.27.1.018
Yongha Choo, Changhwan Kim, Gyeonghwan Yun, Cheewoo Lee
In this study, the harmonic orders of varying magnetic flux density with respect to slot combinations are scru-tinized through a spatial and temporal fast Fourier transform. A three-phase four-pole induction motor is selected, and, as its base model, 36 and 28 slots are set up in the stator and rotor, respectively. Eleven models with different numbers of rotor slots were designed to study torque ripples with respect to slot combinations. The correlation between torque ripple and slot harmonics in a stator and rotor is described thoroughly by comparing the tangential and radial magnetic flux densities in the air gap, tangential force density, and harmonic orders in torque. Some models having deteriorated torque ripples have one or more slot harmonic orders in common in the stator and rotor. The other models exhibit the same commonalities, but a small torque ripple occurs because of the high harmonic orders. Models with 24 stator slots are investigated through the same pro-cedure to generalize the relationship between torque ripple and slot harmonics in 36 stator slots.
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