Analysis of in-bore magnetic field in C-shaped armature railguns

In order to analysis the distribution characteristics of in-bore magnetic field for C-shaped armature electromagnetic railgun, a computational model considering dynamic contact pressure is established. By solving the dynamic equation, the in-bore motion characteristics of the armature are obtained. The distribution of current in the rail and armature is analyzed based on the magnetic diffusion equation and Ampere’s law. On this basis, three simulation models are proposed, which correspond to static state,motion state and motion state considering the velocity skin effect. The magnetic field of the investigated points along the central axes of the armature front end are obtained. The results show that, in static state,the peak magnetic flux density of each investigated point is greater than the other two states. Velocity skin effect leads to a decrease in peak magnetic flux density. The change of motion state has little influence on the peak magnetic flux density of the investigated point that far away from the armature. The calculated results can be used in the electromagnetic shielding design of intelligent ammunition.

Numerical simulation of dynamic large deformation and fracture damage for solid armature in electromagnetic railgun

The design of solid armature of railgun should take full account of its operating conditions and material properties because the armature is subjected to dynamic loading conditions and experiences a complicated electrical,thermal and mechanical process in the interior ballistic cycle.In this paper present,we first introduced a multi-physical field model of railgun,followed by several examples to investigate the launching process.Especially,we used the explicit finite element method,in which material nonlinearity and geometric nonlinearity were accounted,to investigate the deform behaviors of solid armature.The results show that the dynamic mechanical process of armature is dependent on the armature geometry,material and exciting electric current.By the numerical simulation,the understanding of the fracture mechanism of solid armature was deepened.

Study on the influence of armature on the efficiency of reluctance accelerator

The armature is an important part affecting the energy conversion efficiency of a reluctance accelerator.In this paper,six kinds of soft magnetic materials are chosen and four structures are designed for the armature.At first,the circuit and magnetic force are theoretically analyzed.Then the armatures with different materials and structures are used in the simulation,and the performances are compared and analyzed.At last,the experiment verifies the theory analysis and simulation design.It is concluded that the saturation flux density and conductivity of the material are the key factors affecting the armature force,and the optimization of armature structure can effectively restrain the eddy current,reduce negative force and improve efficiency.Compared with cutting slits in solid armatures,laminating the sheets radially can reduce the eddy current more efficiently.Although slitting can prevent the eddy current to a certain extent,meanwhile,it will decrease the magnetic force because of the losing of magnetized volume and the surface area.Hence,choosing the high saturation flux density material and making out the armature with radially_laminated sheets will improve the efficiency of the reluctance accelerator.In this paper,the silicon steel radially_laminated armature is a better choice for the armature design of the reluctance accelerator.

Intelligent Wind Power Unit with Tandem Wind Rotors and Armatures （Optimization of Front Blade Profile）

The authors have invented the superior wind power unit, which is composed of the tandem wind rotors and the double rotational armature type generator without the traditional stator. The large-sized front wind rotor and the small-sized rear wind rotor drive, as for the upwind type, the inner and the outer rotational armatures, respectively, in keeping the rotational torque counter-balanced between both wind rotors/armatures. The unique rotational behaviors of the tandem wind rotors and the fundamental performances of the unit have been discussed at the previous paper. Continuously, this paper investigates experimentally and numerically the flow condition around the wind rotors to know the flow interactions between the front and the rear wind rotors, and optimizes the blade profile in the front wind rotor. The front blade should work fruitfully at the larger radius and had better not work at the smaller radius for giving plenty of wind energy to the rear wind rotor, taking account of the flow interaction between both wind rotors.

An armature structure for 3D shapes

We present a novel armature structure for 3D articulated shapes, called SBall short for skeletal balls, which includes two parts： a one-dimensional skeleton and incident balls. Our algorithm mainly focuses on constructing the armature structure. This structure is based on an approximation skeleton which is homotopy equivalent to the shape. Each ball in the structure connects a skeletal joint and an interior region of the shape. The boundary vertices on the shape surface are attached onto the SBall using the power diagram of the ball set. A bilateral O^tering algorithm and a variational segmentation algorithm are proposed to enhance the quality of SBall. Finally, applications of this structure are discussed.

The Continuation Power Flow Considering Both Generator Excitation Current Limits and Armature Current Limits

在传统连续潮流算法中,发电机无功限制采用定上、下限值来处理,随着有功负荷增加,无功限值通常不变,得到的电压稳定裕度偏大。根据同步发电机的无功出力特性,提出同时计及发电机励磁电流约束和电枢电流约束的连续潮流模型和方法。当相应参数越限时,将发电机节点转换为励磁恒定模型或者电枢电流恒定模型进行计算。所提PV、PEq、PIa节点类型双向转换逻辑可在潮流迭代内进行发电机限制模式的转换,模拟实际系统无功能力的变化。分岔点类型识别模块可以识别崩溃点类型及关键约束。通过新英格兰39节点算例的仿真,证明所提算法是有效的。

Experimental Study on the Expansion Uniformity of Armature

A measurement system has been developed based on high-precision printed probes in printed circuit board （PCB） and steep rising-time probe adapters, which can be applied to study the expansion uniformity of armature in a helical magnetic flux compression generator （HFCG）. The influences of wall thickness and initiation position on the expansion uniformity of armature in HFCG were experimentally investigated. The results show that the armature with thinner wall thickness will easily rupture due to the high pressure of detonation products inside, the armature with larger wall thickness will easily crack due to the tensile stress on the outer surface of the wall, the influence of the end effect on the expansion uniformity can be ignored if the distance between the first group of probe and the initiation point is more than 3 times the armature diameter.

Method of analyzing vibration characteristics of armature system of hermetically sealed electromagnetic relay

Published research is minimal on vibration characteristics of hermetically sealed electromagnetic relay (EMR) ex- posed to mechanical environment. The vibration characteristics of armature system, link contact system with electromagnetic system will cause EMR malfunction. The nonlinear dynamics model of armature systems was studied by considering electro- magnetic attraction force and opposite mechanical force in this paper. Angular displacements of armature under different sinu- soidal vibration conditions are solved in order to obtain the failure mode result from armature system. Vibration tests showed the presented analyzing method is suitable for EMR. The conclusions are instructive for increasing vibration resistance of armature systems of EMR, and are significant for reliability design of switch apparatus.

Modeling of Fault-tolerant Flux-switching Permanent-magnet Machines for Predicting Magnetic and Armature Reaction Fields

The paper develops accurate analytical subdomain models for predicting the magnetic and armature reaction fields in fault-tolerant flux-switching permanent-magnet machines.The entire region is divided into five subdomains,followed by rotor slots,air-gap,stator slots,PM,and external air-gap imported to account for flux leakage.The coil turns and the remanence of magnets are adjusted by keeping the magnetic and electrical loading on the motor constant.The distance between the centers of two adjacent stator slots varies due to the introduction of faulttolerant teeth.According to the variable separation method,the general solution expression of each region can be determined by solving the partial differential systems of equations.The magnetic field distributions of subdomains are obtained by applying the continuity conditions between adjacent regions.Some analytical field expressions are represented as new forms under armature reaction field condition compared to those under no-load condition.Based on the developed analytical models,the flux density distribution and the electromagnetic performance can be calculated under no-load or armature reaction field condition separately.The finite element analysis is carried out to verify the validity of the proposed analytical model.

基于电容吸收拓扑电路的新型磁阻线圈发射器

磁阻线圈发射器具有出口速度一致性好、可靠性高和能源清洁等优点。但是现有磁阻线圈发射器普遍效率较低,限制了其工程应用。为提高发射效率,提出一种基于电容吸收拓扑电路的新型磁阻线圈发射器方案。首先建立了传统二级磁阻式发射器的模型,采用有限元软件进行了仿真计算。结果显示,在电枢经过线圈中心后,驱动线圈中剩余电流产生的磁场会使电枢受到反向电枢拖拽力而减速。针对上述问题,提出一种新型的基于电容吸收拓扑电路的能量回收方案,分析了各阶段的放电特性。计算结果表明:与传统放电电路相比,新型放电电路可以使驱动线圈的剩余电流被电容器吸收实现快速衰减,电枢出口速度由21.46 m/s提高至26.19 m/s,效率由14.50%提高至21.59%。新型放电电路能够对电枢加速后的剩余能量进行回收,明显减小电枢拖拽力,提高了发射速度与能量回收效率。

炮膛间距对枢轨初始接触状态的影响分析

电磁轨道炮炮膛间距直接影响到发射过程中枢轨滑动电接触状态,尤其是起始段炮膛间距变化对电枢烧蚀具有较大影响,将炮膛等效成呈一定角度张开的两条直线,利用角平分线相关特性开展炮膛间距测量,根据炮膛间距实测数据,结合工程实际分析起始段炮膛变化形态并建立对应形态下的枢轨初始接触模型,分析了炮膛装配精度对枢轨初始接触性能的影响,分析结果表明起始段炮膛间距是造成电枢静态受力不均、枢轨接触面积及接触力非对称分布的主要原因,通过不同炮膛变化形态的静态接触试验,进一步验证了理论分析结果。通过分析炮膛间距对枢轨初始接触的影响作用,为枢轨匹配性设计提供理论依据。

YASA轴向磁通永磁电机定子槽漏感计算

定子槽漏感是定子无轭模块化(yokeless and segmented,YASA)轴向磁通永磁电机电感的主要分量,会降低电机的功率因数和最大输出转矩。该文提出定子槽内微小单元磁场能量法计算YASA电机的定子槽漏感,通过建立计及铁心饱和影响的二维等效磁网络模型准确计算槽内微小单元储存的磁场能量,进而计算定子槽漏感。基于所提出的方法,进一步研究定子结构参数以及极槽配合对YASA电机定子槽漏感的影响规律。有限元仿真和实验结果表明,该文所提出的YASA电机定子槽漏感计算方法的可行性和准确性。

虚拟直流电机荷电状态均衡控制

新型电力系统的惯性低,虚拟直流电机控制可以加强系统惯性和阻尼。多储能变换器应该考虑荷电状态(State of charge,SOC)均衡问题,提高系统稳定性。针对虚拟直流电机控制的多储能SOC均衡问题,利用直流电机机端电压和电枢电流的下垂特性,提出引入SOC离差及变均衡系数的变电枢电阻控制;针对下垂引起的电压偏移问题,采用虚拟直流电机转速补偿,用母线电容瞬时功率替代传统虚拟直流电机控制中电压PI控制,给定系统功率需求,减少比例积分环节个数。以两台蓄电池为例,在Simulink中进行仿真,并与参考文献的变电枢电阻函数对比可知,所提控制策略可抑制直流母线电压跌落,调节SOC均衡过程,提高其均衡速度和精度。

无磁轭分块电枢盘式电机齿槽转矩优化设计

为了满足定子无磁轭分块电枢(yokeless and segmented armature,YASA)轴向磁通永磁电机作为车用牵引电机时对输出转矩高平稳性的要求,提出一种基于永磁体径向均匀分段、分组同向偏移的方法来抑制YASA电机的齿槽转矩,以降低转矩脉动。应用三维有限元分析,分别研究了3种不同的永磁体分段方案对齿槽转矩的削弱效果,确定了磁极的最优偏转角度及其对电机综合性能的影响。仿真结果验证了该方法的可行性。YASA电机的齿槽转矩降低了92.62%,额定工况下转矩脉动下降了72.02%,永磁体涡流损耗降低91.28%,同时输出转矩下降不超过5.34%,提高了YASA电机的综合性能。

电磁轨道发射装置材料损伤抑制方法研究现状

电磁轨道发射是利用洛伦兹力在数毫秒内将电枢和负载加速到超高速的发射技术。电枢通过紧固式或填塞式装填在轨道内,在大电流强磁场环境下进行超高速滑动,不可避免伴随有轨道刨削、轨道沟槽、电枢融化和电枢转捩损伤发生。电磁轨道发射器的损伤问题是限制其工程化的关键,针对电枢轨道材料损伤抑制问题,总结国内外电磁轨道损伤机理研究现状,分析电枢轨道4类表面材料损伤成因。针对损伤机理介绍了改进电枢轨道结构、使用新型材料及整流驱动电流3种抑制损伤方案。最后介绍了一种具有高导电性、高导热性、高沸点和低熔点特性的镓基液态金属,讨论了用该金属制备电枢涂层抑制电枢轨道间机械磨损,减轻熔蚀损伤并推迟转捩发生的可行性,并对电磁轨道发射装置损伤抑制研究进行了展望。

电枢及导轨几何参数对电磁轨道发射器电感梯度的影响

电枢是电磁轨道发射器的关键部件,但以往对电感梯度的研究认为电枢距离炮尾部无穷远,忽略了电枢对导轨电感梯度的影响。为此,首先分别建立电磁轨道发射器的二维和三维模型,对比分析了无电枢部分导轨的电感梯度和电枢附近部分导轨电感梯度之间的差异;然后,基于有电枢的电磁轨道发射器三维模型,探究了U形电枢尺寸对电磁轨道发射装置电感梯度的影响。研究结果表明:随着导轨宽度,导轨间距,导轨厚度的增加,无电枢部分导轨的电感梯度和电枢附近部分导轨电感梯度之间的误差均逐渐增加;随着两种电枢宽度的增加,电磁轨道发射器电感梯度呈减小趋势,但变化量较小。

多网络协同的三阶段电枢缺陷检测

电枢是微特电机的重要组成部件,其表面质量直接影响电机运行。当前有关电枢表面质量的检测准确率低下,特征难以把控。为提升信息捕捉效率,实现电枢缺陷的精细划分和识别,提出了一种多网络协同的三阶段电枢检测方法。首先,利用MobileNetV2对电枢图像进行铜线和变阻区域完整性的分类检测;然后,将通过检测的图片利用YOLOv4进行特征识别;最后,基于识别到的检测结果进行模式识别。实验结果表明,该方法可以准确、精细地划分电枢的缺陷。

Induced CTL-S15 gene expression by Bacillus thuringiensis declines susceptibility in Spodoptera exigua

It has been reported that C-type lectins(CTLs),which are pattern recognition receptors of the insect innate immunity response,may compete with Cry toxin for the receptor alkaline phosphatase to decrease its toxicity in insects.However,to date,which CTLs affect larval susceptibility to Bt in Spodoptera exigua is not clear.In this study,33 CTL genes were identified from S.exigua.Based on the number of carbohydrate-recognition domains(CRDs)and the domain architectures,they were classified into three groups:(1)nineteen CTL-S(single-CRD),(2)eight immulectin(dual-CRD)and(3)six CTL-X(CRD with other domains).RT-qPCR analysis revealed that expression levels of SeCTL-S15,IML-4 and CTL-X6 were upregulated after challenge with Bt and Cry1Ab.Tissue and developmental stage expression analysis showed that only SeCTL-S15 was mainly expressed in the midgut and larva,respectively.Knockdown of SeCTL-S15 significantly increased Bt susceptibility,as indicated by reduced survival and larval weight.These results suggest that CTL-S15 might play a vital role in the low susceptibility of larvae to Bt in S.exigua.Our results provide new insights into CTL function in insects.

喷油器衔铁阻尼特性仿真分析

衔铁是喷油器中最重要的执行零件,对喷油器的喷油特性的影响特别大。以某喷油器为研究对象,使用计算流体力学(CFD)的方法详细地研究了衔铁阻尼间隙对衔铁落座过程的影响规律。计算结果表明:衔铁落座初期,阻尼间隙产生的阻尼力很小;衔铁落座后期,阻尼力将迅速增加。当阻尼间隙小于0.050 mm后,衔铁才会在落座中受到较大阻尼力的作用。衔铁底部面积增加,衔铁受到阻尼力将变大。阻尼间隙上下端面平行度增加,衔铁圆周方向受到的阻尼力不均匀程度将变大。

Research on static characteristic of double redundance double nozzle flapper valve based on AMESim

The feedback spring rod of the armature assembly is cancelled in the double redundance double nozzle flapper valve(DRDNFV),and the difficulty of valve core displacement control is increased.Therefore,this paper intends to study the static characteristic of DRDNFV through the AMESet and AMESim simulation.It is explored under the circumstance of the fixed orifices being clogged and experimentally verified on the test bench.The results show that the pressure gain increases and the flow gain decreases with the increasing clogged degree of the fixed orifices on both sides.The zero bias increases synchronously with the increasing clogged degree of the unilateral fixed orifice.The experimental results are basically consistent with the theoretical curves and the theoretical correctness of the simulation model is effectively verified.The results can provide the theoretical reference for design,debugging,maintenance and fault diagnosis of DRDNFV.