Metal–Organic Gel Leading to Customized Magnetic‑Coupling Engineering in Carbon Aerogels for Excellent Radar Stealth and Thermal Insulation Performances

Metal–organic gel(MOG)derived composites are promising multi-functional materials due to their alterable composition,identifiable chemical homogeneity,tunable shape,and porous structure.Herein,stable metal–organic hydrogels are prepared by regulating the complexation effect,solution polarity and curing speed.Meanwhile,collagen peptide is used to facilitate the fabrication of a porous aerogel with excellent physical properties as well as the homogeneous dispersion of magnetic particles during calcination.Subsequently,two kinds of heterometallic magnetic coupling systems are obtained through the application of Kirkendall effect.FeCo/nitrogen-doped carbon(NC)aerogel demonstrates an ultra-strong microwave absorption of−85 dB at an ultra-low loading of 5%.After reducing the time taken by atom shifting,a FeCo/Fe3O4/NC aerogel containing virus-shaped particles is obtained,which achieves an ultra-broad absorption of 7.44 GHz at an ultra-thin thickness of 1.59 mm due to the coupling effect offered by dual-soft-magnetic particles.Furthermore,both aerogels show excellent thermal insulation property,and their outstanding radar stealth performances in J-20 aircraft are confirmed by computer simulation technology.The formation mechanism of MOG is also discussed along with the thermal insulation and electromagnetic wave absorption mechanism of the aerogels,which will enable the development and application of novel and lightweight stealth coatings.

Analysis of temperature field for a surface-mounted and interior permanent magnet synchronous motor adopting magnetic-thermal coupling method

Aiming at obtaining high power density of surface-mounted and interior permanent magnet synchronous motor(SIPMSM),it is important to accurately calculate the temperature field distribution of SIPMSM,and a magnetic-thermal coupling method is proposed.The magnetic-thermal coupling mechanism is analyzed.The thermal network model and finite element model are built by this method,respectively.The effects of power frequency on iron losses and temperature fields are analyzed by the magnetic-thermal coupling finite element model under the condition of rated load,and the relationship between the load and temperature field is researched under the condition of the synchronous speed.In addition,the equivalent thermal network model is used to verify the magnetic-thermal coupling method.Then the temperatures of various nodes are obtained.The results show that there are advantages in both computational efficiency and accuracy for the proposed coupling method,which can be applied to other permanent magnet motors with complex structures.

Effects of Different Spin-Spin Couplings and Magnetic Fields on Thermal Entanglement in Heisenberg XYZ Chain

The effects of spin-spin interaction on thermed entanglement of a two-qubit Heisenberg XYZ model with different inhomogeneous magnetic fields are investigated. It is shown that the entanglement is dependent on the spin-spin interaction and the inhomogeneous magnetic fields. The larger the Ji （i-axis spin-spin interaction）, the higher critical value the Bi （i-axis uniform magnetic field） has. Moreover, in the weak-field regime, the larger Ji corresponds to more entanglement, while in the strong-field regime, different Ji correspond to the same entanglement. In addition, it is found that with the increase of Ji, the concurrence can approach the maximum value more rapidly for the smaller Bi, and can reach a larger value for the smaller bi （i-axis nonuniform magnetic field）. So we can get more entanglement by increasing the spin-spin interaction Ji, or by decreasing the uniform magnetic field Bi and the nonuniform magnetic field hi.

Investigation of Thermal Losses in a Soft Magnetic Composite Using Multiphysics Modelling and Coupled Material Properties in an Induction Heating Cell

The complex interaction between material properties in an induction heating circuit was studied by multi physics simulation and by experimental verification in a full-scale laboratory heater. The work aims to illustrate the complexity of the system of interacting materials, but also to propose a method to verify properties of soft magnetic composite materials in an integrated system and to identify which properties are the most critical under different circumstances and load cases. Heat losses at different loads were primarily studied, from DC currents to AC currents at 15, 20 and 25 kHz, respectively. A FE model for magnetic simulation was correlated with a corresponding model for heat simulation. The numerical model, as well as the established input material data, could be verified through the experimental measurements. In this particular study, the current loss in the litz wire was the dominant heat source, thus making the thermal conductivity of the SMC the most important property in this material.

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.

Temperature Field Analysis of Mine Flameproof Outer Rotor Permanent Magnet Synchronous Motor with Different Cooling Schemes

Aiming at the problem of temperature rise of mine flameproof outer rotor permanent magnet synchronous motor,based on the fluid structure coupling method,the temperature distribution of motor under three cooling schemes of air cooling and water cooling are calculated respectively.For the structure I air cooling system,the influence of different number of heat sink on the maximum temperature rise and pressure drop of fluid channel is analyzed,and the parameters of heat sink are optimized.For the structure II air cooling system,the influence of setting fillet at the turn back of the fluid channel on the head loss in the fluid domain of the motor is analyzed,and the influence of different fillet radius on the head loss and the maximum temperature rise in the fluid domain is obtained.For the structure II water cooling system,the influence of different water flow speed on the maximum temperature rise of the motor is analyzed,and the influence of different assembly clearance of modular stator teeth and yoke on the maximum temperature rise of the motor is analyzed.The cooling effect and temperature rise distribution characteristics of the three cooling schemes are compared and analyzed.Finally,a water-cooled prototype is manufactured,and the temperature rise experiment is carried out,and the influence of the thermal deformation of fluid channel,stator yoke and stator teeth on the maximum temperature of the motor is analyzed.The results show that the calculated temperature field after considering the thermal deformation is closer to the experimental value,which verifies the accuracy of the calculation results,It also provides a reference for the selection and design of the cooling structure of the same type of PMSM electric roller.

Entanglement in a two-qubit Heisenberg XXZ chain with different Dzyaloshinskii-Moriya couplings and an inhomogeneous magnetic field

Ground state entanglement and thermal entanglement of a two-qubit Heisenberg XXZ chain in the presence of the different Dzyaloshinski-Moriya interaction and inhomogeneous magnetic field are investigated.By the concept of concurrence,we find that the inhomogeneity of the magnetic field may make entanglement last for a long time and the critical temperature is dependent on Jz and b.The entanglement can be increased by increasing the temperature in some cases.We also find that the x-component parameter Dx has a higher critical temperature and more entanglement for a certain condition than the z-component parameter Dz.

Coupled Electromagnetic-thermal Analysis of Segmented PM Consequent Pole Flux Switching Machine

Compact stator structure of flux switching machines(FSMs)encompassing both permanent magnets(PMs)and armature winding slots(AWS)attract research interest whenever high power and density are the basic requirements.However,it also results in temperature rises owing to heat generation by electromagnetic power losses degrading the electromagnetic performance and affecting machine performance.In this study,a segmented permanent magnet(SPM)consequent pole FSM(SPM-CPFSM)is developed,which provides a stator cooling channel(duct)for improved heat dissipation to avoid demagnetization of PM as well as overheating.Furthermore,this study investigates detailed electromagnetic performance analysis and prediction of temperature variation in various machine parts owing to the heat generated by iron,copper,and magnet eddy current losses utilizing coupled electromagnetic-thermal analysis accounting for magnetic flux density variation.In comparison with the 2D analysis,the developed 3D coupled-field analysis more accurately predicts electromagnetic performance and temperature distribution.Analysis reveals that a cooling duct at the stator significantly assists in stator heat dissipation in the axial direction ensuring a safe operating condition of the PMs as well as machine parts to avoid overheating.

基于磁热耦合法的非对称混合磁极永磁电机热分析

针对传统内置永磁电机损耗高、发热量大的问题,提出非对称混合磁极永磁电机拓扑结构.介绍非对称混合磁极永磁电机的拓扑结构,对比分析两者的电磁特性与损耗分布特性.针对非对称混合磁极永磁电机分布式绕组的结构特点,对绕组进行等效处理,确定等效导热系数,建立集中参数热网络模型.建立单向磁热耦合模型,计算电机各部件的温度分布,验证了热网络模型的正确性.考虑到温度对永磁材料的影响,建立双向磁热耦合模型,对比分析不同电流密度对电机温升的影响规律.试制一台样机并搭建温升试验平台进行温升试验,验证了新型拓扑结构的有效性与合理性以及磁热双向耦合法计算结果的准确性.

Lumped-Parameter Thermal Network Model and Experimental Research of Interior PMSM for Electric Vehicle

A 25kW interior permanent magnet synchronous machine(IPMSM)applied to the electric vehicle is introduced in the paper.A lumped-parameter thermal network model is presented for IPMSM temperature rise calculation.Furthermore,a 3D liquid-solid coupling model considering the assembly clearance is compared with the 2D lumped-parameter thermal network model.Finally,a dynamometer platform for temperature rise measurement is established to verify the above-mentioned methods,which obtains the measured efficiency map at rated load case and overload case.At the same time,the measured no-load back electromotive Force(EMF),load line input voltage and load current are gathered.Thermocouple PTC100 is used to measure the temperature of the stator winding and iron core,and the FLUKE infrared thermal imager is applied to measure the surface temperature of PMSM and controller.Testing result shows that the lumped-parameter thermal network have a high accuracy to predict each part temperature.

磁热双向耦合内置式电磁感应加热辊的设计与仿真

对磁热双向耦合内置式电磁感应加热辊进行设计与仿真分析,根据麦克斯韦方程和温度微分方程,分别建立电磁场和温度场数学模型,通过磁热双向耦合方式进行求解。利用有限元仿真软件设计正交试验,研究线圈与辊内壁间距、电流大小、电流频率、线圈匝数对升温时间和温度均匀性的影响,并通过反向传播神经网络得到最佳参数组合。结果显示,线圈与辊内壁间距16mm、电流大小105A、电流频率11.7kHz、线圈匝数104为最佳参数组合,此时升温至平均温度250℃的时间为784s,温度均匀性为1.7527。

设施园艺电驱移动平台轮毂电机设计及其磁-热耦合性能

针对设施园艺作业场景下电驱移动平台的低速大扭矩牵引作业需求,该研究设计了一种减速内转子轴向磁通轮毂电机,建立电机的电磁有限元模型并分析其电磁和损耗特性。考虑到绕组电阻率受温度变化影响,构建基于热网络法的轮毂电机磁-热耦合改进模型。与台架试验结果相比,基于改进模型获得的转矩预测值较传统模型的精度提高了5.33%,验证了模型的正确性。利用改进模型分析了温度和相电流对电机转矩特性的影响,仿真结果表明,输出转矩随电机温度增加而降低;在0~20 A,电机平均输出转矩与相电流呈线性关系。试验结果表明,轮毂电机功率随转速增加而增大,峰值功率可达4.59 kW,而转矩基本保持恒定;在转速450~900 r/min、转矩300~600 N·m时,电机效率高达93.2%。研究结果可为轴向磁通电机初步设计与多场耦合影响下电机性能分析提供思路。

基于磁-热双向耦合的牵引电机温度场分析

为探究牵引电机温升问题,本文以某大型矿用电动车轮边牵引电机为研究对象,建立电机三维流动与传热耦合求解的有限元模型;并给出基本假设与相应的边界条件,采用磁-热双向耦合方法模拟计算电机的电磁场和温度场,在此基础上,分析该电机在低速满载工况下的温度场分布特性。采用这种分析方法可以实现对电机温度场特性的准确分析而且有助于电机冷却系统合理设计,为更大功率的电机综合物理场的准确计算提供了理论依据。

径向磁液轴承定子温升及热变形研究

提出一种新型的磁液轴承,以电磁悬浮支承为主、静压支承为辅,实现双重支承,并可以实时调控。通过建立磁液轴承的有限元分析模型,对其进行流-固-热耦合求解,得到轴承的流场、温度、应力及应变分布云图。通过调整轴承系统的结构参数(进油孔直径和线圈匝数)及运行参数(输入电流、进油流量、转子转速)分别进行有限元建模,利用ANSYS软件进行仿真分析,求解不同参数对轴承温升及定子热变形的影响规律。结果表明:流体造成的压力在进油孔内最高为1 MPa,流体在油膜处流速最高为0.8 m/s;轴承定子温度分布对称,有利于散热。研究结果为磁液轴承系统的优化设计提供理论依据。

高温高功率密度永磁伺服电机电磁热耦合设计

介绍了一种适应高温、高功率密度永磁伺服电机热设计方法。通过国内外技术发展现状分析,结合高温环境应用,分析永磁交流伺服驱动电机在适应高温、高功率密度方面的电磁、热设计技术难点,通过提升永磁交流伺服电机电磁、热联合设计方法,提升高功率密度永磁伺服电机的高温适应性。

E型分块定子永磁同步电机热分析及优化

分块定子永磁同步电机作为一种新型电机拓扑结构,具有高容错性、高转矩密度等特点,同时存在电机损耗大的问题,威胁到电机性能的稳固性。以E型分块定子永磁同步电机为研究对象,分析电机损耗机制,研究不同运行工况下电机损耗变化规律;采用磁热双向耦合法对电机进行热分析,并基于热分析结果采用响应面优化方法对电机进行多目标优化设计。优化后,电机平均输出转矩提升了14.15%,涡流损耗降低了55.99%,平均温升降低了12.62%。最后通过实验验证了双向磁热耦合法的准确性及优化设计的有效性。

基于磁热耦合扁线电机温升计算及影响因素分析

由于扁线绕组永磁电机具有槽满率高、散热好和绕组端部紧凑等优点,在新能源汽车领域受到广泛关注。以一台额定转速6000r/min的车用扁线绕组永磁同步电机为例,建立一种电磁场和温度场耦合仿真模型,采用单向和双向的耦合温升计算方法,计算损耗作为热源对电机温升的影响,并对仿真结果进行试验验证。同时,采用双向磁热耦合方法探讨在不同运行工况下冷却液流量、种类和入口温度对扁线电机温升的影响规律。结果表明:双向磁热耦合温升计算结果与试验结果更为一致,验证了双向磁热耦合仿真分析结果的准确性。通过计算不同影响因素下各部件的温度分布,在两种工况下随着冷却液流量的不断增加或冷却液入口温度的降低,电机各部件温度下降明显。分别以空气、不同浓度的乙二醇水溶液、冷却油、水作为冷却液时,冷却水的冷却效果最好。

永磁同步电机磁固热多物理场耦合振动噪声分析

针对永磁同步电机的电磁振动噪声多物理场耦合问题,在磁固耦合的基础上,考虑温度场对电机结构和电磁特性的影响,通过有限元法提出一种磁固热多物理场耦合模型,分析在热应力和电磁力共同作用下电机的结构变形,突出对比强弱耦合变形情况下电机电磁力及振动噪声情况。以一台6极36槽内置式永磁同步电机(Interior Permanent Magnet Synchronous Motor,IPMSM)为研究对象,综合考虑磁场、温度场和结构场多物理场耦合作用,建立永磁同步电机有限元模型,用ANSYS Workbench准确计算电机各种损耗并进行温度反馈,并通过实验验证模型准确性。结果表明,考虑温度分布和结构变形有助于准确预测和评估电机的振动噪声水平。

中频变压器铁心的磁-热耦合计算与实验

基于中频变压器磁耦合的电力电子变压器是新型电力系统中的关键装置。考虑频率对超薄硅钢磁化及损耗特性的影响,基于电磁场与温度场间接耦合的计算方法,对一台40 kV·A/400 Hz超薄硅钢中频变压器不同频率条件下铁心的电磁场与温度场分布进行求解,并开展变压器模型的空载实验,得到不同频率下的空载损耗和温升分布。通过仿真与实验数据的比较,误差均在允许范围内,验证了磁-热耦合分析的准确性,为中频变压器铁心散热和材料选择提供参考依据。

不同冷却器挡板结构对高压永磁电机换热特性的影响分析

为了降低高压永磁电机的温升,以一台额定功率为1400 kW的高压永磁电机为研究对象,基于计算流体力学和传热学理论,优化了冷却器挡板结构,建立电机三维耦合分析模型,对电机进行流热耦合分析,计算并比较了两种冷却器挡板结构下的电机各个通风道的流体流动及传热特性,从对流传热优化的场协同角度,得出了不同冷却器结构下的电机温升和温度分布规律,为高压永磁电机通风结构优化设计提供参考依据。