An internal ballistic model of electromagnetic railgun based on PFN coupled with multi-physical field and experimental validation

To accelerate the practicality of electromagnetic railguns,it is necessary to use a combination of threedimensional numerical simulation and experiments to study the mechanism of bore damage.In this paper,a three-dimensional numerical model of the augmented railgun with four parallel unconventional rails is introduced to simulate the internal ballistic process and realize the multi-physics field coupling calculation of the rail gun,and a test experiment of a medium-caliber electromagnetic launcher powered by pulse formation network(PFN)is carried out.Various test methods such as spectrometer,fiber grating and high-speed camera are used to test several parameters such as muzzle initial velocity,transient magnetic field strength and stress-strain of rail.Combining the simulation results and experimental data,the damage condition of the contact surface is analyzed.

Research on heat dissipation characteristics of magnetic fluid bearings under multiple field coupling effects

This paper analyzes the sources of heat losses in magnetic fluid bearings,proposes various cou-pling relationships of physical fields,divides the coupled heat transfer surfaces while ensuring the continuity of heat flux density,and analyzes the overall heat dissipation pathways of the bearings.By changing parameters such as input current,rotor speed,and inlet oil flow rate,the study applies a multi-physics field coupling method to investigate the influence of different parameters on the temper-ature field and heat dissipation patterns of the bearings,which is then validated through experi-ments.This research provides a theoretical basis for the optimal design of magnetic fluid bearing sys-tems.

Coupled Numerical Simulation of Electromagnetic and Flow Fields in a Magnetohydrodynamic Induction Pump

Magnetohydrodynamic(MHD)induction pumps are contactless pumps able to withstand harsh environments.The rate of fluid flow through the pump directly affects the efficiency and stability of the device.To explore the influence of induction pump settings on the related delivery speed,in this study,a numerical model for coupled electromagnetic and flow field effects is introduced and used to simulate liquid metal lithium flow in the induction pump.The effects of current intensity,frequency,coil turns and coil winding size on the velocity of the working fluid are analyzed.It is shown that the first three parameters have a significant impact,while changes in the coil turns have a negligible influence.The maximum increase in working fluid velocity within the pump for the parameter combination investigated in this paper is approximately 618%.As the frequency is increased from 20 to 60 Hz,the maximum increase in the mean flow rate of the working fluid is approximately 241%.These research findings are intended to support the design and optimization of these devices.

Transient multi-physics behavior of an insert high temperature superconducting no-insulation coil in hybrid superconducting magnets with inductive coupling

A transient multi-physics model incorporated with an electromagneto-thermomechanical coupling is developed to capture the multi-field behavior of a single-pancake(SP)insert no-insulation(NI)coil in a hybrid magnet during the charging and discharging processes.The coupled problem is resolved by means of the finite element method(FEM)for the magneto-thermo-elastic behaviors and the Runge-Kutta method for the transient responses of the electrical circuits of the hybrid superconducting magnet system.The results reveal that the transient multi-physics responses of the insert NI coil primarily depend on the charging/discharging procedure of the hybrid magnet.Moreover,a reverse azimuthal current and a compressive hoop stress are induced in the insert NI coil during the charging process,while a forward azimuthal current and a tensile hoop stress are observed during the discharging process.The induced voltages in the insert NI coil can drive the currents flowing across the radial turns where the contact resistance exists.Therefore,it brings forth significant Joule heat,causing a temperature rise and a uniform distribution of this heat in the coil turns.Accordingly,a thermally/mechanically unstable or quenching event may be encountered when a high operating current is flowing in the insert NI coil.It is numerically predicted that a quick charging will induce a compressive hoop stress which may bring a risk of buckling instability in the coil,while a discharging will not.The simulations provide an insight of hybrid superconducting magnets under transient start-up or shutdown phases which are inevitably encountered in practical applications.

STUDY OF TOPOLOGY OPTIMIZATION FOR THERMO-STRUCTURAL COUPLING FIELD

A number of critical problems of topology optimization concerning the thermostructural coupling field axe studied at length. The governing equations and topology optimization model for the thermal-structural coupling field axe derived, with an adjoint method for sensitivity analysis of the thermo-structural coupling field proposed. The optimization algorithm for coupling field topology optimization is investigated and a flowchart of coupling field topology optimization presented. The theory and algorithms axe implemented and verified by two numerical examples.

特高压并联电抗器铁芯振动及噪声特征研究

特高压并联电抗器因其铁芯是以铁芯饼与气隙垫块交替堆叠而成的结构特点,导致其运行过程中振动强度远超同电压等级的变压器,易出现振动超标等问题,现有计算方法对特高压并联电抗器铁芯振动特征还无法准确表征。鉴于此,该文针对1台特高压并联电抗器的铁芯振动机理及产生的噪声进行研究,结合磁-结构-声多场耦合分析,对铁芯所受麦克斯韦力及磁致伸缩力进行仿真计算,将结构场计算结果进行快速傅里叶变换后作为载荷激励进而计算由电抗器振动产生的噪声,并单独分析磁致伸缩力和麦克斯韦力对电抗器铁芯振动造成的影响。结果表明:电抗器运行过程中电抗器铁芯旁轭中部产生的振动最剧烈,电抗器周围产生的噪声最大。对比麦克斯韦力与磁致伸缩力对电抗器铁芯振动的影响发现,同时考虑两个力时铁芯振动小于未考虑磁致伸缩力的情况,证明影响电抗器铁芯振动的两个力存在相互衰减作用。

Multi-physical field coupling simulation of TCVI process for preparing carbon/carbon composites

To prepare Carbon/Carbon (C/C) composites with advanced performance, the thermal gradient chemical vapor infiltration (TCVI) process has been optimized by simulation. A 2D axisymmetric unstable model was built, which included convection, conduction, diffusion, densification reactions in the pores and the evolution of the porous medium. The multi-physical field coupling model was solved by finite element method (FEM) and iterative calculation. The time evolution of the fluid, temperature and preform density field were obtained by the calculation. It is indicated that convection strongly affects the temperature field. For the preform of carbon/carbon composites infiltrated for 100 h by TCVI, the radial average densities from simulation agrees well with those from experiment. The model is validated to be reliable and the simulation has capability of forecasting the process.

基于场量传递的流动-传热-凝固过程耦合计算模型及其应用

水平连铸是铜板带铸轧加工流程中的重要环节,其核心物理过程包括流动、传热及凝固,实验研究存在诸多不便和局限性,因此往往采用数值模拟方法对铸坯质量和组织进行分析。为进一步提高模拟准确性和完整性,本工作建立了铜板坯水平连铸流动-传热过程与传热-凝固过程耦合数值模型,并设计了不同网格之间的高精度场传递算法;通过控制输入参数和边界条件实现了流动-传热模型和传热-凝固模型之间温度场量一致性,解决了传统模型无法耦合流场计算凝固组织的难题,并通过生产试验证实了耦合模拟结果的准确性。

COMSOL Multiphysics在锂离子电池中的应用

作为一种具有前景的能量存储系统,锂离子电池需要进一步提高能量密度、功率密度、可靠性和循环稳定性,以满足不断增长的大型能源存储、电动汽车和便携式电子设备需求。当前对锂离子电池的实验研究仍然面临多个挑战,这些挑战包括电解液的导电性和安全性、高能量负极的沉积-剥离机制的优化、高能量正极的循环电压和容量维持、高电流条件下的界面极化和容量释放,以及在极端电流-温度-针刺条件下的热失控管理等问题。这些问题涉及到电-化-力-热等多个场的耦合作用,需要进行协同优化处理。COMSOL Multiphysics提供了一种可行的工具,通过求解多物理场耦合的连续方程,能够同时考虑载流子浓度、电流密度、电-化学势、温度、应力/应变和几何形态等综合信息的演化。本文概述了该工具在锂离子电池的电解液、负极和正极设计等方面的研究,并聚焦于多场耦合对电池性能的综合影响、多场耦合模拟方法以及理论模拟与实验表征的结合。最后,本文对理论与实验联合研究中的多场和多尺度问题进行了展望。

Thermal management by manipulating electromagnetic parameters

Electromagnetic absorbing materials may convert electromagnetic energy into heat energy and dissipate it.However,in a high-power electromagnetic radiation environment,the temperature of the absorbing material rises significantly and even burns.It becomes critical to ensure electromagnetic absorption performance while minimizing temperature rise.Here,we systematically study the coupling mechanism between the electromagnetic field and the temperature field when the absorbing material is irradiated by electromagnetic waves.We find out the influence of the constitutive parameters of the absorbing materials(including uniform and non-uniform)on the temperature distribution.Finally,through a smart design,we achieve better absorption and lower temperature simultaneously.The accuracy of the model is affirmed as simulation results aligned with theoretical analysis.This work provides a new avenue to control the temperature distribution of absorbing materials.

Multi-physics coupling field finite element analysis on giant magnetostrictive materials smart component

This study presents a new method to solve the difficult problem of precise machining a non-cylinder pinhole of a piston using embedded giant magnetostrictive material (GMM) in the component. We propose the finite element model of GMM smart component in electric, magnetic, and mechanical fields by step computation to optimize the design of GMM smart com-ponent. The proposed model is implemented by using COMSOL multi-physics V3.2a. The effects of the smart component on the deformation and the system resonance frequencies are studied. The results calculated by the model are in excellent agreement (relative errors are below 10%) with the experimental values.

Fast three-dimensional radiation field characterization in largescale nuclear installations

The requirement of the fast three-dimensional radiation field calculation is raised during the decommissioning of large-scale nuclear installations. The most often used methods, such as the Monte Carlo and the discrete ordinates methods, have shortcomings in their simulations of such problems. The coupled Monte Carlo–point kernel computational scheme is developed to meet the requirement. The facility is separated into the source region and the bulk shielding region, with a common interface. The transport within the source region is simulated using the Monte Carlo method, which is by nature good at treating complex geometries. The radiation field in the bulk shielding region is treated by the point kernel approach to avoid the extremely expensive computation for deep penetration problems. The flow rate through the interface,which is given by the Monte Carlo simulation, is considered as the equivalent surface source for the point kernel calculation. Test calculations from simplified typical waste storage facilities have been performed to validate the coupled scheme by comparing them with the results conducted by the Monte Carlo method directly. The good agreement of the results, as well as the significant saving in computing time, indicates that the coupled method is suitable for the fast three-dimensional radiation field calculation.

基于多场耦合的涡轮叶片静强度计算分析

涡轮叶片是航空发动机最昂贵和最关键的部件之一,它们在高交变负荷、极端温度、侵蚀和腐蚀的恶劣工作条件下运行。为了保障涡轮的正常运行以及防止事故的发生,在涡轮叶片静强度设计过程中需要考虑热-流-固多场耦合作用;建立了涡轮叶片的多场耦合计算流程,综合考虑热负荷、离心负荷和气动负荷对涡轮叶片静强度设计的影响;通过对涡轮叶片进行静强度分析,得到了叶片在热负荷、离心负荷和气动负荷综合作用下的应力分布,确定了涡轮叶片强度危险点的位置和最大等效应力,可以为涡轮叶片的寿命预测提供依据。

海上CO_(2)埋存井井筒温度压力影响因素研究

准确预测CO_(2)埋存过程中井筒温度压力场以及CO_(2)的物性参数变化对安全埋存至关重要。为此,建立了埋存井井筒温度、压力与CO_(2)物性参数的耦合计算模型,计算得到了实例井井筒温度压力分布以及CO_(2)物性参数随井深的变化规律,并对注入参数对于井筒温度压力分布影响规律进行分析。研究结果表明:井筒内CO_(2)流体的流速、努塞尔特数和对流换热系数随井深的增加而增大,密度、黏度、摩阻系数、导热系数和普朗特数随井深增加而减小,定压比热容在温度压力综合作用下有一定波动;注入温度对井筒压力和井底温度压力影响很小;注入速率增大会使相同井深处温度降低、压力升高,调节注入速率可以在对压力影响较小的同时有效调节井筒温度分布;注入压力的变化对压力梯度几乎无影响,在压力较大时对温度梯度影响较大,通过调节注入压力可以有效调节井筒压力分布。研究结果可为海上CO_(2)埋存井井筒完整性的准确评价提供理论基础。

复合材料身管电磁轨道炮轨道结构变形分析

以复合纤维材料缠绕下的电磁轨道炮身管为研究对象,通过研究其工作原理建立瞬态3D耦合仿真模型,并基于LS-DYNA软件对模型进行电磁-热-结构变形场耦合计算,分析轨道在发射工况下的变形位移情况。结果表明轨道上应力波、振动以及临界速度共振现象的存在,说明预应力的施加会提高结构的稳定性,改变缠绕角度和缠绕层厚度会对结构刚度产生影响。

基于多物理场计算的微波加热均匀性改善研究

针对微波加热过程中存在温度分布不均匀的问题,提出利用多端口加热方式,通过多物理场耦合计算分析了端口布局、位置、数量以及功率配比对微波加热马铃薯块均匀性的影响。仿真计算结果表明,在四端口馈入时,端口分布于腔体四面,四个端口坐标分别为(-55,-162.5,70)、(162.5,-55,70)、(55,162.5,70)和(-162.5,55,70),且四端口馈入功率比为200∶200∶300∶300时,微波加热均匀性效果最佳。

适用于直流断路器的大电流快速开关分闸特性

快速开关分闸稳定性是影响直流断路器开断性能的关键要素。文中对大电流快速开关的双弹簧永磁操动和电磁斥力双动机构的分闸过程,用有限元方法进行电磁、热和位移等多物理场耦合计算,分析了永磁操动机构驱动线圈是否有必要投入以及不同驱动线圈电流对双动机构分闸特性的影响。结果表明:在永磁操动机构驱动线圈投入的情况下,可提前将永磁吸力抵消,进而避免电磁斥力因做功时间较短而引起分闸回弹现象;由于分闸初期电磁斥力非常大,永磁操动机构驱动线圈的投入对分闸初期的速度影响较小;在电磁斥力消失后,永磁操动机构驱动线圈电流在一定范围内越大,到达额定开距的速度越大,为避免其造成分闸反弹,应合理选择驱动线圈电流值。将仿真结果与实际样机分闸特性曲线进行对比,二者具有较好的一致性,验证了仿真方法的正确性。

Numerical Simulation of Temperature Distribution and ThermalStress Field in a Turbine Blade with Multilayer-Structure TBCs by a Fluid–Solid Coupling Method

To study the temperature distribution and thermal-stress field in different service stages, a two-dimensional model of a turbine blade with thermal barrier coatings is developed, in which the conjugate heat transfer analysis and the decoupled thermal-stress calculation method are adopted. Based on the simulation results, it is found that a non-uniform distribution of temperature appears in different positions of the blade surface, which has directly impacted on stress field. The maximum temperature with a value of 1030 ℃ occurs at the leading edge. During the steady stage, the maximum stress of thermally grown oxide （TGO） appears in the middle of the suction side, reaching 3.75 GPa. At the end stage of cooling, the maximum compressive stress of TGO with a value of-3.5 GPa occurs at the leading edge. Thus, it can be predicted that during the steady stage the dangerous regions may locate at the suction side, while the leadine edge mav be more Drone to failure on cooling.

“双端节能”铝电解槽的热电仿真计算及模拟研究

本文采用ANSYS软件对400 kA铝电解槽内部热场及炉帮形状进行研究,通过对侧部安装微通道热管集热器的试验槽仿真模拟,确定了集热功率与电解槽侧壁温度及槽内炉帮厚度之间的关系,进而实现了准确解析槽内热场的目标。这对于进一步探究能量流对电解槽内热特性的影响以及研究铝电解的“双端节能”具有十分重要的理论和实际意义。

微波辅助煤炭脱硫的多物理场耦合计算研究

针对高硫煤脱硫研究中存在实验研究周期长,且实验过程中可能由于温度分布不均匀导致热点或热失控的安全隐患问题,多物理场耦合计算能够发挥重要作用。通过多物理场耦合计算的方法对微波辅助高硫煤脱硫过程进行研究,分析微波辐照功率、氧化剂配比、辐照温度、辐照时间对煤样脱硫率的影响,并分析搅拌速率对加热均匀性的影响,从而得到微波脱硫的最佳工艺条件,并对微波脱硫最佳工艺条件下的电场和温度场分布进行分析。结果表明,在最佳工艺条件下,煤样脱硫率较高,电场和温度场分布较均匀且无明显热点产生。