Permanent Magnets Design and Magnetic Field Analysis of Multi-disc Coreless Permanent Magnet Synchronous Motor

This paper presents a new multi-disc coreless permanent magnet synchronous motor whose permanent magnets are arranged in the “Halbach array”. Unit motor combined structure is adopted to simplify processing technology of the motor. Airgap magnetic flux density is increased taking advantage of high remanence and coercive force of NdFeB permanent magnet material and high gathering magnetism function of Halbach array. This also makes coreless motor possible. The structure and the characteristics of the motor using Halbach array are also introduced. The FEM analysis has been done to build the mathematical model and study the magnetic field characteristics of the motor. And finally the interrelated design parameters of permanent magnet and arrangement between unit motors are determined according to the results of die FEM analysis.     

Amelioration of Coreless Permanent-Magnet Disk Synchronous Motor Based on FEM: Motor With Wedge Airgap

A novel coreless PM (permanent magnets) disk synchronous motor, consisting of a single stator in the middle and twin rotors on both sides, is proposed in this paper. NdFeB magnets with high coercivity and high remanence are used, and a special arrangement of PM—Halbach array is employed to enhance the magnetic flux density in the airgap. Cylindrical PM array is stuck on the rotor to avoid the eddy current wastage, which is caused by reciprocal movement between the rotor and the PM array. The stator contains a winding molded by high mechanical integrity plastic without any core. Besides, the wedge airgap is designed to reduce the equivalent length of the airgap, and hence to advance the performance of the motor. The analysis of the magnetic field has been done by FEM method. An example motor of the design in this paper has been made, the magnetic flux density of which reaches 0.53 T, and the efficiency of the motor is above 92%. The motor has a better performance in each phase, and the aim of amelioration is achieved.     

Transient Analysis for Magnetic Circuit of a Novel Synchronous Motor Basing on Controllable Flux

The paper refers to a novel permanent magnet motor with composite-rotor, to solve the difficulties of extend speed by “flux weakening”. The rotor is composed of two rotor segments: one is made of AINiCo magnet and the other of NdFeB. Relying on high coercive force and high remnant magnetic flux density quality of NdFeB, permanent magnet motor could get enough air gap magnetic fields. On the other way, by making using of low coercive force characteristics of AINiCo magnet, die permanent motor could be changed the orientation and strength of magnetization when applying a pulse of magnetizing (demagnetizing) current, thus magnetic flux in air gap could be varied over wide range. To achieve the aim, the paper analyzes magnetization process of permanent magnet and transient magnetic circuit in the motor, and then computes the distribution of air gap magnetic field in different magnetization by using finite element method. The numeral results show the validity of the scheme.     

Simplified Calculation of Open Domain of Magnetic Field in Engineering

Mass electromagnetism phenomena occur in open domain. But because of the difficulty of calculation, open domain problems are often simplified as equivalent model in the finite space in order to save time of modeling and analyzing in the computer. Taking a disk coreless permanent magnet synchronous motor (PMSM) as an example, the FEM analysis is done to simplify open domain of magnetic field. Aiming at a difficult problem of the modeling and solving to the open domain of magnetic field, it is very important to reduce fact domain effectively. The FEM analysis has been done to prove that the method reducing the open domain into the smallest domain could obtain approximately the accurate results, at the same time the EMS memory and the time are reduced obviously. So the intention of simplification is achieved.     

Design of Polar Anisotropic Sintered NdFeB Ring-Type Permanent-Magnet for Brushless DC Motor

A Four polar anisotropic sintered NdFeB PM with high surface flux density was developed using dry pressing process with pulse magnetizing fields. In this paper, effects of filling density, magnetic field intensity, distribution of the cavity, and of the way of pre-magnetized powder for the high performance polar anisotropic sintered NdFeB PMs were studied. It can be seen that magnets produced by pre-magnetized powder process shows magnetic surface flux's maximum value that is 6,300 G due to pre-magnetized effects and that the back e.m.f. of Brushless motor, is 5.4 Vp/p per 1000 rpm, an increase about 35% above the conventional segment magnet.     

室温磁制冷磁体用量的估算

根据主要的永磁体材料磁化性质和可能的室温磁制冷材料的磁热性质,利用磁路定理并假定了通常使用的循环换热流体的压力差上限来计算磁制冷功率和永磁体体积之间的关系,进而说明室温磁制冷机的制冷量的受约束情况以及实用可能性。通过对两种典型的磁路进行的计算对比,发现在使用高磁场时使用中空圆柱形磁聚焦方式更有效,而在获得低于1T的磁场时普通的救生圈环形磁路更为有效。     

Critical Heat Flux of Blast Furnace Hearth in China

The critical heat flux surveys of thirteen Chinese blast furnaces were carried out.The mathematical model of hearth bottom was established and the temperature field was simulated by utilizing the method of inverse problem based on the collected parameters and temperature data.The critical heat flux and dangerous critical heat flux of hearth were defined and analyzed as well as the initial and investigative critical heat flux of hearth,and the influences of thermal conductivity and residual thickness of carbon bricks on critical heat flux were discussed.The relationships between critical heat flux of stave and hearth bricks were also compared.It is found that the dangerous critical heat flux of these blast furnaces ranged from 9.38 to 57kW/m2.Therefore,there was no uniform critical heat flux of hearth due to the structure design,refractory materials selection,construction quality of hearth and other factors.The heat flux should be lower than the critical heat flux with corresponding thickness of carbon bricks to control the erosion of hearth.The critical heat flux of stave would be much lower than that of hearth bricks with the air gap.However,the critical heat flux of stave should be higher than that of hearth bricks when gas existed between furnace shell and staves.     

铁磁试件静载拉伸时应力磁化的反转效应

 以20钢含V型缺陷平板试样为研究对象,通过试验方法和ANSYS仿真方法对试样在拉伸载荷下的应力分布进行反复加载卸载分析,测量了试样表面规定路径的切向和法向的漏磁场分布;分析了V型缺陷对磁记忆信号的影响以及固定位置的磁场值随应力的变化关系;最后将试验结果与模拟结果进行对比,发现试验结果与模拟结果具有很好的一致性。在应力小于50MPa时磁场值随应力的增加而减小,在应力大于50MPa时磁场值随应力的增加而增加。变化关系表现出了明显的应力磁化反转现象,磁化反转位置在50MPa(约是最大应力的30%)。     

Liquid flow on a rotating disk prior to centrifugal atomization and spray deposition

Video observations of the flow patterns that develop on a rotating disk during centrifugal atomization and spray deposition, and subsequent metallographic studies conducted on solid skulls removed from the disk after processing, have indicated a circular discontinuity or hydraulic jump, which is manifested by a rapid increase in the thickness of the liquid metal and by a corresponding decrease in the radial velocity. A mathematical model has been developed that is capable of predicting both the occurrence and location of the jump, and the associated changes in the thickness profile and in the radial and tangential velocities of the liquid metal. Good correlations have been observed between model predictions and the flow patterns observed on the skull after atomization, and the effects of changes in material and operational parameters such as kinematic viscosity, volume flow rate, metallostatic head, and disk rotation speed have been quantified. Liquid metal flow is controlled primarily by the volume flow rate and by the metallostatic head prior to the hydraulic jump and by the centrifugal forces after the jump. The implications of these observations in terms of the atomization process are discussed.     

永磁球形电动机定子线圈座的应变分析

利用气隙磁通密度解析模型和洛仑兹力公式建立了球坐标系下空心定子线圈所受切向电磁力和径向电磁力的解析模型.利用定子壳体和线圈座的有限元模型计算定子线圈座在电磁力作用下的应变,分析了定子壳体厚度、线圈座连接杆长度和直径对应变的影响.最后利用有限元法和解析法对样机进行分析并对结果进行比较,验证了解析模型的正确性和准确性.分析表明,当定子壳体厚度和连接杆直径线性减小而连接杆长度线性增大时,定子线圈座在电磁力作用下产生的应变量在一定范围内线性增加,然后显著增加.      

Numerical Simulation of Level Magnetic Field

TheLMF (LevelMagneticField)technologybasedonstaticmagneticfieldcanbeusedtoimprovecontinuouscasting ,suchasforreducingimpactonnarrowsidesofshell ,eliminatinglargenonmetallicinclusions ,preventingmoldfluxentrappingandim provingslabcleanliness ,etc[1,2 ] .Theeffectofstaticmagneticfieldonsolutebehaviorandcrystallizationduringsolidificationwasinvestigated[3 ] .Theknowl edgeanddesignofmagneticfieldisveryimportantbaseofLMFtechnology .However ,themagneticfieldwasgenerallytakenasaone dimensionalfie…     

薄硅钢收卷内应力及无芯筒料卷心形坍塌机理

 某薄取向硅钢复卷线采用了恒张力收卷方案,卸卷后无芯筒料卷约有5%的概率发生心形坍塌,经济损失严重。为了研究心形卷产生机理及影响因素,降低坍塌几率,基于弹性力学叠加原理,建立了料卷收卷-卸卷的连续内应力分布模型;进一步基于压力埋管理论分析了无芯筒薄料卷心形坍塌过程,确定了坍塌区层数;测量了12组带厚为0.23、0.283 mm的心形卷的屈曲半圆心角与屈曲区层数,测量值与理论预测值基本吻合,验证了所提理论的准确性。分析了钢带厚度和粗糙度、橡胶层等效径向刚度对内应力的影响。研究表明,随钢带厚度和粗糙度、橡胶层等效径向刚度的减少,料卷心形坍塌概率及坍塌层数增大;该规律与现场观察一致。通过减小橡胶层厚度、增加橡胶层弹性模量可增大等效径向刚度,大幅减小料卷压应力,降低心形坍塌概率和坍塌区层数。     

炉缸内流动传热特性与侵蚀监测模型

 为了分析实际工况下高炉炉缸内流动与换热特性并对炭砖内侵蚀线进行预测,运用了计算流体力学(CFD)和二维快速反推算法的方法对炉底进行了数值仿真计算。研究结果表明,全尺寸炉底CFD模拟较好地展示了炉底流固区域的温度场和流场特征,测点温度与历史热电偶测温值小于5.2%,吻合效果较好;当炉体内存在气隙时,气隙左右分别形成极热区与极冷区,这与历史数据中热电偶温度骤变的现象吻合,且气隙厚度分别为10、20、30 mm时气隙左右温差相对于无气隙分别为原来的14.7、18.9、21.4倍;二维快反计算推演出了“象脚型”侵蚀的形状,最大侵蚀的位置在铁口下方1~3 m内,最小残余厚度与实际测值误差为13.5%,这与高炉实际侵蚀情况十分吻合。     

Effect of geometry and green density on the anisotropic sintering shrinkage of axisymmetric iron parts

Sintering shrinkage of prior cold compacted iron rings with different geometry (height to wall thickness ratio) and green density in the 6.5–7.3?g/cm³ range was investigated. It displays a minimum at an intermediate green density. Axial, tangential and radial shrinkages are different, due to the gradients of green density along the axial and the radial directions. Therefore, the effect of height on shrinkage and its anisotropy is the result of their effect on the stress distribution in the green parts during cold compaction, and the resulting green density and deformation experienced by the powder. Anisotropy decreases on increasing shrinkage.     

Numerical Simulation and Experimental Study of F-EMS for Continuously Cast Billet of High Carbon Steel

A final electromagnetic stirring model was developed for billet continuous casting of high carbon steel using the commercial software ANSYS and CFX, and the numerical model was validated by the magnetic flux density measured under a Teslameter CT-3. The magnetic flux density and fluid flow in the liquid pool at the location of final electromagnetic stirring (F-EMS) were calculated by the present numerical model. Meanwhile, the plant trials were carried out to determine the optimum current intensity and frequency of F-EMS for the continuously cast billet of high carbon steel. The numerical results show that, through increasing the current intensity by 100 A, the corresponding increases of magnetic induction intensity, tangential electromagnetic force and flow velocity at the solid/liquid interface in the strand are 0.025 T, 1933 N/m³ and 6.9 cm/s, respectively. Moreover, the industrial trial results showed that for the continuously cast billet of 60 steel, the optimum current intensity and frequency of F-EMS, which is 8.2 m from the meniscus, are respectively 380 A and 6 Hz. With the optimum F-EMS parameters, the significant improvement of center segregation of billet is achieved, and the center carbon segregation index in billet reaches 1.04.     

Stress calculation in roasted iron-ore pellets on cooling

A method is proposed for calculating the stress in roasted zonal fluxed pellets. The method is based on the appearance of a stress state at the boundary zones with different solidification temperatures of the slag inclusions on cooling. The stress state is calculated for Kachkanar pellets with different positions of the hematite and magnetite zones. It is shown that, on cooling annealed zonal pellets in air, tensile normal stress appears in the radial direction at the boundary of the magnetite core and the hematite shell. The presence of a three-zone structure in the pellets (magnetite core + hematite shell + surface magnetite film) facilitates the redistribution of normal stress over the cross section. Increasing the thickness of the surface magnetite film reduces the tensile stress in the radial direction at the boundary of the core and the shell. As a result, the pellet strength is increased. On cooling roasted pellets with a hematite core and a magnetic shell in a neutral atmosphere, tensile normal stress appears in the tangential direction, tending to reduce the pellet strength.     

圆坯凝固末端电磁搅拌作用下的流动与传热行为

以特殊钢圆坯连铸为研究对象, 建立了研究凝固末端电磁搅拌作用效果的三维耦合数值模型.利用分段计算模型获得末端电磁搅拌区域钢液流动与凝固的实际状态, 并采用达西源项法处理凝固末端钢液在糊状区的流动, 研究了不同电磁搅拌工艺参数下的电磁场分布及钢液的流动与传热特征.通过测量搅拌器中心线磁感应强度和铸坯表面温度验证了模型的准确性.研究结果表明: 电流强度每增加100 A, 搅拌器中心磁感应强度增加19.05 mT, 电磁力随着电流强度的增加显著增大.在20~40 Hz范围, 随着电流频率的提高, 中心磁感应强度略微下降, 但电磁力仍有所增加.在搅拌器区域, 液相穴内的钢液在切向电磁力的作用下旋转流动, 其切向速度随着电流强度和频率的增加而变大.末端电磁搅拌可促进钢液在圆坯径向的换热, 随着电流强度和频率的提高, 铸坯中心轴线上的钢液温度降低, 同时末端搅拌位置处的中心固相分率增加.      

应用波理论预测旋转盘离心雾化膜状分裂区的粉末尺寸

应用平面和圆柱液膜破碎的波理论研究了旋转盘离心雾化膜状分裂区的粉末尺寸的预测方法;推导了最快增长的液膜破碎的波数方程,建立了旋转盘外液膜厚度与液膜径向位置的关系,并用数值方法进行了求解;计算的液膜破碎长度和粉末粒径与文献中的实验数据基本吻合,表明本文所提出的预测方法是可行的。