电磁轨道发射中炮口电弧的抑制

采用一种导通时阻抗极低的外触发开关作为旁路器件, 在电枢即将出膛前开通此消弧器件, 使回路电流从器件流过, 从而达到抑制甚至消除炮口电弧的目的。对比试验表明, 在触发了消弧开关的试验中, 出膛时炮口电压显著降低, 轨道电流几乎全部流过消弧器件, 高速摄影亦显示电弧亮度明显降低, 消弧器件可有效抑制炮口电弧。通过比较触发信号与器件导通信号, 发现消弧器件的导通时刻较触发信号时刻有一定的延迟, 这在一定程度上影响了消弧器件抑制电弧的性能。     

电磁轨道炮性能的数值模拟

 本文介绍一种简单的数值计算模拟，它可以模拟轨道炮的主要性能。模型中考虑了由于炮膛壁烧蚀引起的电枢等离子体质量的增加和各种阻力的影响。这些阻力包括弹丸与壁之间的摩擦力，等离子体粘性及空气阻力等。用一个经验关系表征它们的影响。我们把等离子体等效成一个可变电阻负载，而不管它与电离度有关性质的细节。数值计算结果与实验结果比较表明符合程度是满意的。     

电磁轨道炮的物理原理

近年来,一种新的武器概念进入公众视野。它就是基于电磁弹射原理制造的电磁轨道炮。美国人用于航空母舰上飞机起飞的新的电磁弹射也基于同一原理。它是物理学和电工学用于国防技术的典型事例。电磁轨道炮是一种动能武器,就是依靠发射弹丸的动能摧毁目标。它的工作原理是将电磁能转换成动能,可称电磁发射。当然电磁发射的也不一定是用于武器的弹丸。它有更广泛的用途。     

串联型双轨增强电磁轨道炮电路模拟

建立了包括脉冲电源模块和电磁轨道炮的全电路模型,实现了从电源放电至电磁轨道炮发射过程的全电路模拟。根据电源放电与洛伦兹力加速的耦合方程组,在电路模型内将电源的基本单元封装成子电路模块、弹丸受力运动模型转化为电路解耦模块,建立了针对24个基本单元组成的电源网络驱动串联型双轨增强电磁轨道炮的电路模型。将模拟结果与实验结果进行对比,电流模拟结果偏差2.6%,电枢出膛速度模拟结果偏差9.8%,模拟与实验结果基本一致,验证了模型方程和模拟方法的可靠性和合理性。     

C型固体电枢3维有限元电磁发射计算

对轨道型固体电枢电磁发射的电磁过程进行了研究,建立了基于麦克斯韦准静态A-Φ场方程的3维静枢电磁发射数值模型。利用ANSYS有限元电磁模块结合发射装置的实测参数,对电枢在静枢模型下的电磁发射进行了模拟。计算结果表明:馈入相同电流加载波形时,流经C型电枢的电流密度、磁通量以及电磁发射过程中所受电磁力,在不同时刻的内部分布、峰值和大小均与文献计算结果相符。     

C型固体电枢3维有限元电磁发射计算

对轨道型固体电枢电磁发射的电磁过程进行了研究,建立了基于麦克斯韦准静态A-Φ场方程的3维静枢电磁发射数值模型。利用ANSYS有限元电磁模块结合发射装置的实测参数,对电枢在静枢模型下的电磁发射进行了模拟。计算结果表明：馈入相同电流加载波形时,流经C型电枢的电流密度、磁通量以及电磁发射过程中所受电磁力,在不同时刻的内部分布、峰值和大小均与文献计算结果相符。     

分流器形式炮口消弧装置的电路模拟优化与试验

针对轨道炮电枢出炮口时拉弧问题,提出了一种基于分流器形式的炮口电弧抑制方案。以固体电枢为研究对象,采用Simulink软件根据发射器与消弧装置的电气参数建立含有炮口消弧装置的发射系统仿真模型,目的是通过对消弧装置电气参数不同阻抗值的仿真计算,实现消弧装置电气参数与发射系统电气参数的最佳匹配,达到降低消弧支路对电枢出炮口速度的影响,同时有效地抑制炮口电弧。由于与消弧装置串联的电枢前方轨道阻抗在消弧支路阻抗中占比很大,通过消弧装置阻抗电阻、电感优化调整,实现电枢在膛内运动起始阶段,消弧支路的阻抗远大于电枢支路的阻抗,发射电流大部分都流过电枢,保证了电枢的加速运动。随着电枢向炮口方向运行,消弧支路阻抗快速减小,同时在磁通压缩作用下,消弧支路中电流快速增加,电枢支路电流减小,但由于电枢前后方磁场对其都是推进作用,电枢出炮口速度基本不受影响,保持较高的系统效率;电枢出炮口后,消弧支路的阻抗小于电弧的阻抗值,建立合理的电弧快速消引条件,消弧支路电流远大于电枢上电流,发射系统的剩余能量可通过消弧装置释放,降低炮口拉弧对发射性能的影响。经过消弧装置的电阻和电感多参数值的计算与分析,最后确定与文中发射系统匹配的消弧装置电阻约为1 mΩ,电感约为0.1 μH。结合发射装置结构,设计出的消弧装置电阻为1.32 mΩ,电感为0.124 μH,在搭建的发射系统仿真模型中对其进行了充电电压3 kV等级的发射仿真计算,在充电电压3 kV的发射能量等级下进行了消弧发射试验,仿真结果与试验结果具有较好的一致性,消弧效果良好。     

管身对中口径电磁轨道炮的影响分析

以脉冲电流作为激励的电磁轨道炮无可避免地在不锈钢管身上感应出巨大涡流,涡流不仅自身损耗能量,而且削弱电枢的推进力,降低发射效率。为深入研究管身对电磁轨道炮的影响,结合场路模型计算了电磁轨道炮系统的发射效率和涡流能耗,讨论了不同管身结构和材料下的发射效率,进一步分析了管身对电磁轨道炮力学特性的影响。结果表明：基于10 MJ脉冲电源的中口径电磁轨道炮,其不锈钢管身将大幅削弱系统的发射效率,管身涡流能耗比炮口动能的一半还多;采用层压式结构的高导磁材料作为管身,发射效率的提升尤为明显;管身对电枢轴向力的削弱是导致发射效率下降的根本原因,对电枢径向力的削弱则不利于电枢和轨道的良好接触,从而增加接触电阻,降低发射效率;但是对身管各部件径向力的减小有助于降低身管所需预紧力。     

管身对中口径电磁轨道炮的影响分析

以脉冲电流作为激励的电磁轨道炮无可避免地在不锈钢管身上感应出巨大涡流,涡流不仅自身损耗能量,而且削弱电枢的推进力,降低发射效率。为深入研究管身对电磁轨道炮的影响,结合场路模型计算了电磁轨道炮系统的发射效率和涡流能耗,讨论了不同管身结构和材料下的发射效率,进一步分析了管身对电磁轨道炮力学特性的影响。结果表明:基于10MJ脉冲电源的中口径电磁轨道炮,其不锈钢管身将大幅削弱系统的发射效率,管身涡流能耗比炮口动能的一半还多;采用层压式结构的高导磁材料作为管身,发射效率的提升尤为明显;管身对电枢轴向力的削弱是导致发射效率下降的根本原因,对电枢径向力的削弱则不利于电枢和轨道的良好接触,从而增加接触电阻,降低发射效率;但是对身管各部件径向力的减小有助于降低身管所需预紧力。     

Boundary-layer effect on railgun muzzle voltage

Measured values of railgun muzzle voltage exceed those predicted from simple armature models by several tens of volts. This excess voltage is called the contact potential and may represent a substantial fraction of the power dissipated in the armature. A simple two-dimensional model for the conductivity and velocity boundary layers has been used to calculate the electric field in the region near the rail surfaces. Calculations were performed for parameters characteristic of the University of Tennessee Space Institute (UTSI) 1-cm square-bore railgun. These calculations showed that the electric field decreased across the boundary-layer thickness and predicted contact potentials from 12.5 to 88.7 V, depending on the choice of boundary-layer parameters     

Study of a railgun plasma armature

An experimental and theoretical study of a railgun plasma is presented. The experimental results have been obtained by recording the voltage and current variations as well as the spectral emission of the plasma. The gas pressure, helium, or air in contact with the exploding foil has been varied from 0.1 to 2 MPa. The apparatus consisted of a test chamber simulating a railgun facility. To complete the study, some measurements of the plasma characteristics in the 500-kJ EMA 1 railgun system have been recorded. It is shown that the resistance of the plasma, which is 15 mΩ at 10 kA, decreases to 0.2 mΩ at 500 kA. These results indicate the effect of the energy flow to the walls and that of the ionization potential of the gas in contact with the exploding foil at lower currents     

Equilibrium lengths of railgun plasma armatures

Recent data have shown that the length of railgun plasma armatures increases with bore size. The mechanisms for plasma growth and mass loss are treated analytically through a simple thermodynamic model in which mass is added through ablation of bore materials and lost through friction. It is assumed that at the bore wall, a thin boundary layer is formed in the plasma in which the velocity is sufficiently slow that the boundary layer is left behind the bulk of the plasma. Using the scaling relations of J.D. Powell and J. Batteh (1983), a functional relationship between the plasma length l_p and bore height h of the form l_p=kh^α, where α≃0.68. Using the model developed in the present work, a linear relationship between l_p and h is derived, but the proportionality factor depends on temperature, plasma conductivity, velocity, and boundary-layer thickness. Predictions of the model are interpreted in the light of available data. The model is shown to predict lengths which are in reasonable agreement with the observed data     

分布储能式电磁轨道炮效率分析

分布储能式电磁轨道炮在长导轨发射中具备高发射效率优势,为实现分布储能式电磁轨道炮的恒流特点,建立可供发射器参数、结构设计参考的仿真模型尤为重要。针对口径为60 mm×80 mm的矩形轨道炮,根据电流波形的平稳性要求,沿导轨方向设置电流馈入点,诊断电枢位置并分时序触发各馈入点电源,以测试分布储能式电磁轨道炮的工作性能。在COMSOL三维磁场中建立矩形导轨-电枢模型,基于电流和磁场的多物理场耦合有限元分析得到磁场和电流的分布,并利用电磁场仿真结果实现电流趋肤效应下轨道电阻梯度计算。基于MATLAB SIMULINK平台对电容储能型脉冲功率电源模块建立电气电路;分析分布储能式电磁轨道炮非线性时变的动态特性并建立轨道及电枢阻抗模型,计算正向电磁力、滑动摩擦力构造电枢的运动方程,并使用信号电路建立电枢-导轨模块,通过Simulink测量模块连接两个隔离的网络,仿真计算得到导轨电流及电枢的出膛速度。设计了总储能为4.16 MJ的分布式储能轨道炮,结果显示,电容预充电压为10.8 kV时,导轨长为3 m的分布式电磁轨道炮可将1 kg的弹丸加速至1.4 km/s,与炮尾集中式电磁轨道炮相比,系统发射效率可提升约3%。     

Thermodynamic and electrical properties of railgun plasma armatures

A model including the nonideal effects is presented that describes the plasma composition, equation of state, internal energy, and electrical conductivity for a very dense and relatively cool plasma like that which exists in a railgun plasma armature. Results are presented for four elements of specific interest for plasma armatures-hydrogen, lithium, aluminum, and copper-for pressures ranging from 1 to 1000 atm and temperatures ranging from 10000 to 50000 K. The results are presented in a graphical format which should prove useful to modelers and experimentalists investigating plasma armatures     

Effect of acoustic field parameters on arc acoustic binding during ultrasonic wave-assisted arc welding

As a newly developed arc welding method, power ultrasound has been successfully introduced into arc and weld pool during ultrasonic wave-assisted arc welding process. The advanced process for molten metals can be realized by utilizing additional ultrasonic field. Under the action of the acoustic wave, the plasma arc as weld heat source is regulated and its characteristics make an obvious change. Compared with the conventional arc, the ultrasonic wave-assisted arc plasma is bound significantly and becomes brighter. To reveal the dependence of the acoustic binding force on acoustic field parameters, a two-dimensional acoustic field model for ultrasonic wave-assisted arc welding device is established. The influences of the radiator height, the central pore radius, the radiator radius, and curvature radius or depth of concave radiator surface are discussed using the boundary element method. Then the authors analyze the resonant mode by this relationship curve between acoustic radiation power and radiator height. Furthermore, the best acoustic binding ability is obtained by optimizing the geometric parameters of acoustic radiator. In addition, three concave radiator surfaces including spherical cap surface, paraboloid of revolution, and rotating single curved surface are investigated systematically. Finally, both the calculation and experiment suggest that, to obtain the best acoustic binding ability, the ultrasonic wave-assisted arc welding setup should be operated under the first resonant mode using a radiator with a spherical cap surface, a small central pore, a large section radius and an appropriate curvature radius.