300 kA铝电解槽电磁流场数值计算研究

本文基于某铝厂300 kA铝电解槽基本结构及尺寸,运用大型有限元软件ANSYS建立铝电解槽电、磁、流场模型,对该铝厂铝电解槽进行数值仿真计算。电解质层中电流主要为垂直分布,铝液层电流出现较大的水平方向分量值;磁场x方向沿短轴为反对称分布,y方向沿长轴大体上呈现反对称分布,z方向大体上沿长轴呈反对称分布;铝液-电解质界面最大隆起高度为3.28 cm。探究了铝电解槽电磁流场分布情况,为铝电解槽节能降耗生产提供理论指导。

基于电磁场—流场—温度场耦合分析的电缆支架温升计算及实验验证

随着大长度大截面的电力电缆在隧道的普及,电缆支架因涡流损耗造成的线损、以及发热产生温升形变等问题也日益严重。文中采用有限元数值计算方法,以110 kV单相电缆及其钢支架为研究对象,进行了电磁场—流场—温度场耦合计算。将电磁场计算得到的涡流损耗作为温度场计算的热源载荷,同时考虑空气自然对流的散热方式,从而计算出电缆支架的温度分布。最后进行电缆支架温升实验,将仿真得到数据和实验数据进行对比,验证电缆支架温升计算的准确性和有效性。

非平衡感应耦合等离子体流场与电磁场作用机理的数值模拟

以航天领域中研究再入飞行器热防护系统的感应耦合等离子体(inductively coupled plasma, ICP)风洞为研究对象,通过流场-电磁场-化学场-热力场-湍流场多场耦合求解研究ICP 风洞流场与电磁场的分布特性及其相互作用机理.数值模拟中,基于热化学非平衡等离子体磁流体动力学模型准确模拟了空气ICP 的高频放电、焦耳加热、能量转化、粒子内能交换等过程,通过多物理场耦合计算模拟得到了100 kW 级ICP 风洞内空气等离子体的电子温度、粒子数密度、洛伦兹力、焦耳加热率、速度、压强、电场强度的分布规律.研究结果表明:在感应线圈区靠近等离子体炬壁附近,等离子体流动处于热力学非平衡状态;洛伦兹力对感应线圈区空气粒子的动量传递和电子热运动起着控制作用.

单相隔离开关损耗发热的电磁场与流场耦合计算

针对某型号的单相隔离开关损耗发热进行计算,基于Workbench平台的磁场流场耦合仿真保证了数据传递的有效性。在进行温升仿真计算时,借助电磁场仿真软件Maxwell考虑实际工况计算热源,将计算热源作为流场仿真软件Fluent的源项输入,计算出隔离开关温度场。结果表明：在环境温度25℃下,温度最高部分主要集中在导电杆处,最高可达63℃。通过对比,仿真计算的结果与实验结果接近,此仿真计算能很好地指导隔离开关的温升性能设计。

热镀锌锌锅的电磁-流体耦合计算

在锌锅的流动及传热状态的数值模拟中,感应加热器边界条件的处理是计算的关键和难点。以某连续热镀锌锌锅作为研究对象,采用ANSYS软件的电磁场模块,计算得到锌锅加热器中洛仑兹力及焦耳热的分布,并将其作为加热器区域流场计算时动量及能量的源项,从而实现了对加热器中电磁场和流场耦合的锌锅全场计算。与前人给定热流密度的处理方法相比较,本文方法更真实地逼近了实际物理模型与过程。计算结果表明,熔沟中的锌液在洛仑兹力作用下呈螺旋状地由中心熔沟向两侧熔沟流动,加热器出口截面上的最大速度约为0.77m/s,大部分区域中的速度均大于0.3m/s,计算结果与文献中实际锌锅运行时的数据吻合良好,表明了本文方法的正确性和有效性。

300 kA铝电解槽电、磁、流多物理场耦合仿真

将标量电位法和磁标量位法相结合,开发了铝电解槽电场、磁场耦合计算模块,并导出了电磁力场以计算磁流体三维湍流流场及其界面波高．计算结果表明,垂直磁场基本呈现为反对称关系,水平电流对磁流体运动有显著影响,铝液流场形态基本对称,呈现为4个较大漩涡,铝液界面向中部隆起．将计算结果与测试值进行了比较,表明该方法能够有效用于铝电解槽生产和设计的物理场仿真计算分析．

现代大型铝电解槽内复杂物理场的仿真计算与优化

总结了国内外在铝电解槽电热场、热应力场及电磁流场方面的研究进展,指出当前多物理场仿真计算算法的不足,介绍了最新开发的＂液（电解质）-液（铝）-气＂和＂液-气-固（颗粒）＂两类三相流模型、多物理场（电、磁、热、流、力、浓度分布场等）、磁流体稳定性和电流效率三维耦合仿真模型与算法,并提出基于多相-多场耦合仿真的大型铝电解槽结构与生产工艺综合优化方法,发现大型铝电解槽在3.7~3.9 V低电压下高效、低电耗、低排放、稳定运行的状态空间,并确立相应的工艺实现条件。

300KA预焙阳极铝电解槽物理场的计算机仿真

以某厂SY300型预焙槽为基础简化模型,利用solidworks软件建立铝电解槽三维物理模型。在使用部分假设条件、合理理想分割场域、多场共享模型信息和结果的前提下,运用COMSOL Multiphysics有限元软件和Matlab软件分别建立了物理模型的电场,磁场,流场及其耦合场的计算模块。在COMSOL平台上,求解更换阳极时电解槽的电场和磁场,对电流密度和磁场分布进行仿真、分析和讨论。针对不同槽膛形状给出了相应的铝液流场。研究表明,水平电流对磁流体运动有显著的影响,铝液的形态基本呈对称状态。

铝电解槽熔体涡运动对界面变形影响仿真研究

维持较小的铝电解槽内铝液—电解质界面变形对控制极距(ACD)进而降低电解能耗具有重要的意义。以某300 kA预焙阳极铝电解槽为例,采用有限元分析软件ANSYS和计算流体力学软件CFX进行了电磁流场仿真,解析得到铝液—电解质的界面变形和熔体涡结构分布情况。研究发现,界面在涡结构的内部区域下凹而在涡外部边缘则向上隆起,相邻大涡连接区域的界面隆起高度较大;提高槽内水平电磁力分布的对称性可使熔体涡运动更为均匀,也是减小界面波动并维持规则的界面变形的有效途径。

Directional growth behavior of a(Al) dendrites during concentration-gradientcontrolled solidification process in static magnetic field

The large and small sized Cu（solid）/Al（liquid） couples were prepared to investigate the directional growth behavior of primary a（Al） phase during a concentration-gradient-controlled solidification process under various static magnetic fields（SMFs）.The results show that in the large couples,the α（Al） dendrites reveal a directional growth character whether without or with the SMF.However,the 12 T magnetic field induces regular growth,consistent deflection and the decrease of secondary arm spacing of the dendrites.In the small couples,the α（Al） dendrites still reveal a directional growth character to some extent with a SMF of ≤5 T.However,an 8.8 T SMF destroys the directional growth and induces severe random deflections of the dendrites.When the SMF increases to 12 T,the a（Al） dendrites become quite regular despite of the consistent deflection.The directional growth arises from the continuous long-range concentration gradient field built in the melt.The morphological modification is mainly related to the suppression of natural convections and the induction of thermoelectric magnetic convection by the SMF.

基于微波传输线原理的持水率测量方法

基于微波传输线原理和油水混合流体介电性质,研究了终端短路双线传输线持水率测量方法,从理论上推导了测量线路端口S参数同介电常数的关系式,在S参数和持水率之间建立了对应关系。在此基础上,对理论解和电磁场计算数值解进行了对比,验证了理论分析的正确性。为了考虑流固耦合效应对电磁场的影响,对模型内部复杂流体进行了多相流数值模拟,根据模型内部结构对测量灵敏度的影响,提出了优化测量装置结构参数的方法,使之能够满足高持水率测量准确性和灵敏性的需求。

Novel magneto-rheological fluid damper for passive force/torque feedback

The damper is capable of providing a continuously variable dampering force/torque in response to a magnetic field. It consists of an upside cap and an underside cap with a rotor located between them, the magneto-rheological （MR） fluid is filled into the gaps between the rotor and the caps. When the viscosity of the MR fluid increases under the influence of the magnetic field, the movement of the rotor will be resisted. The output torque is made up of the torque caused by the magnetic field, the torque caused by the plastic viscosity of the MR fluid, and the torque caused by the coulomb friction. The viscous torque can be calculated by a simple method and the frictional torque can be obtained by experiments. The torque dependent on the magnetic field is obtained by electromagnetic finite dement analysis. Experiments are done on the damper prototype and the validity of the design is verified.

Analytical and Experimental Studies of Linear MHD Propulsor

A two dimensional mathematical model was developed to predict the performance characteristics for direct current, linear channel MHD propulsion system in a closed loop environment. The results of analytical and experimental studies of the linear channel MHD propulsor are described. Compared with the data of experiment, the correctness of the computation program is validated.

Simulation of electromagnetic-flow fields in Mg melt under pulsed magnetic field

The effects of a pulsed magnetic field on the solidified microstructure of pure Mg were investigated.The results show that microstructure of pure Mg is considerably refined via columnar-to-equiaxed growth under the pulsed magnetic field and the average grain size is refined to 260？？ under the optimal processing conditions.A mathematical model was built to describe the interaction of the electromagnetic-flow fields during solidification with ANSYS software.The pulsed electric circuit was first solved and then it is substituted into the magnetic field model.The fluid flow model was solved with the acquired electromagnetic force.The effects of pulse voltage frequency on the current wave and on the distribution of magnetic and flow fields were numerically studied.The pulsed magnetic field increases melt convection,which stirs and fractures the dendritic arms into pieces.These broken pieces are transported into the bulk liquid by the liquid flow and act as nuclei to enhance grain refinement.The Joule heat effect produced by the electric current also participates in the microstructural refinement.

Quantum current and Coulomb blockade effect in the mutual inductance coupled mesoscopic system with active source

Based on the charge discreteness,the property of quantum current and the effects of Coulomb blockade have been investigated for the mutual inductance coupled mesoscopic system with active source in external magnetic field.The relationships between quantum current and the conditions of Coulomb blockade in the coupled dual-ring system are given here.

Two—Electron Energy Spectrum in a Parabolic Quantum Dot Under a Magnetic Field

Two interacting electrons in a harmonic oscillator potential under the influence of a perpendicular homo-geneous magnetic field are considered. The energies of two-electron quantum dots with the electron-LO-phonon couplingas a function of magnetic field are calculated. Calculations are made by using the method of few-body physics withinthe effective-mass approximation. Our results show that the electron-LO-phonon coupling effect is very important insemiconductor quantum dots.

Optimal Design for Open MRI Superconducting Magnet with Active Shielding

The optimal design method for an open Magnetic Resonance Imaging （MRI） superconducting magnet with an active shielding configuration is proposed. Firstly, three pairs of current rings are employed as seed coils. By optimizing the homogeneity of Diameter Sphere Voltnne （DSV）, the positions and currents of the seed coils will be obtained. Secondly, according to the positions and currents of the seed coils, the current density of superconducting wires is determined, and then the original sections for the coils can be achieved. An optimization for the homogeneity based on the constrained nonlincar optimization method is employed to determine the coils with good homogeneity. Thirdly, the magnetic field generated by previous coils is set as the background field, then add two coils with reverse current, and optimize the stray field line of 5 Gauss in a certain scope. Finally, a further optimization for the homogeneity is used to get Final coils. This method can also be used in the design of other axisynmaetfic superconducting MRI magnets.

Double ESOs-based field-oriented control for PMSM drive system with current sensorless

A novel double extended state observers(ESOs)-based field-oriented control(FOC)strategy is developed for three-phase permanent magnet synchronous motor(PMSM)drive systems without any phase current sensor.In principle,two current sensors are essential parts of the drive system for implementation of the feedback to achieve high accuracy control.For this purpose,the double ESOs are created to provide feedback stator currents instead of actual current sensors.The first one of the double ESOs is designed to estimate the benchmark value of q-axis stator current,which is a primary premise;While the second is designed to estimate real-time stator currents of d-axis and q-axis simultaneously.The resultant double ESOs can rapidly and accurately give estimation of the actual currents of a-axis,b-axis and c-axis,and the synthesized double ESOs-based FOC strategy for PMSM drive system without any current sensors has satisfactory control performance and strong robustness.Numerical experiments validate the feasibility and effectiveness of the proposed scheme.

DC casting of light alloys under magnetic fields

The working principle of LFEC（Low frequency electromagnetic casting） process developed in Northeastern University, China was introduced and the metallurgical results of LFEC were discussed according to the casting practices. The low frequency field around the mold produces Lorenz force, which can be divided into two parts： one is the potential force which will be balanced by a pressure gradient of the liquid and results in the formation of a convex surface meniscus and improves the surface quality; the other is the rotary force which stirs the liquid in the mold to refine the microstructures and homogenize the distribution of alloying elements. LFEC can refine microstructures remarkably, improve surface quality of the ingots, depress macrosegregation and eliminate cracks. Some new technologies, such as horizontal direct chill casting under low-frequency electromagnetic field （HLEC）, DC casting of hollow billets under electromagnetic fields （HBEC）, electromagnetic modifying of hypereutectic A1-Si alloys（EMM）, air film casting under static magnetic field （AFCM）, and multi-ingots casting under low-frequency magnetic field （MLFEC） were developed based on LFEC.

A Plane-Symmetric Inhomogeneous Cosmological Model of Perfect Fluid Distribution with Electromagnetic Field Ⅰ

A plane-symmetric inhomogeneous cosmological model of perfect fluid distribution with electro-magnetic field is obtained. F12 is the non-vanishing component of electromagnetic field tensor. To get a deterministic solution, we assume the free gravitational field is Petrov type-Ⅱ non-degenerate. Some physical and geometric properties of the model are also discussed.