直流电弧等离子体点火器射流特性研究

采用光谱仪测量了等离子体点火器出口射流的发射光谱,利用玻尔兹曼曲线斜率法计算了射流的电子温度,并通过电离平衡方程计算了射流气体温度,获得点火器出口射流长度、射流速度、电子温度和射流温度随弧电流及进口氩气流量的变化规律。并分析了航空等离子体电弧射流中是否可使用电子温度来代替射流气体温度。实验表明：弧电流随着进口氩气流量的增大而减小;出口射流长度和速度随弧电流的增大而增大,随进口氩气流量的增大先增大后减小;出口电子温度、电子密度和射流温度随弧电流的增大而升高,随氩气流量的增大而降低。     

DPF中子源中子产生机理成因分析

基于等离子体的动量和能量守恒方程,利用一维雪耙模型,描绘出等离子体焦点装置放电电流壳层的动力学行为,得到整个电流壳层在两极间的运动情况,计算了电流壳层的加速段时间,计算结果与实验符合得很好.实验测量了等离子体鞘的反箍缩速度、加速阶段速度、聚焦阶段箍缩速度和崩溃阶段速度及中子发射异向性因子,均证明焦点装置中子产生机制主要由束靶机制控制.     

热等离子体

虽然已许多工业应用开发了热等离子体工艺，但是由于经济和竞争的原因，和／或再现性和可靠性方面的原因，它们未能作为一种制造技术得到广泛认可，本文着重评估现在对以下课题的了解：１）等离子体炬和吹弧（直流或交流）传热弧以及射频炬的性能；２）确认的工业应用，其重点是切割，焊接，喷涂，传热弧回收，再加热和纯化，再加热金属熔化，还原熔炼，化学运行以及废物破坏；３）最近对等离子体炬在电源，阴极（热的冷和热）阳极（     

等离子体切割的弧特性研究

基于弧柱双区域近似的简单理论,研究了空气等离了体切割产生的等离子体弧特性,给出了不同工作条件（空气流速及喷嘴直径）下,弧的半径、电压及喷嘴出口处压强随弧电流变化的计算结果。研究结果表明,计算与实验结果符合得好。同时讨论了空气流速及喷嘴直径对等离子体功率及作用力的影响。     

托卡马克中离子回旋频率范围内快波电流驱动的研究

在现在和未来的先进托卡马克装置中,离子回旋频率范围内的快波电流驱动都是一种不可或缺的非感应电流驱动方式。本文利用全波方程得到波电场和磁场分布,代入扩散系数并求解Fokker-Planck方程,采用自行编写的程序对快波在等离子体中的电子吸收功率和驱动电流等物理量进行数值求解。初步研究了快波频率和等离子体温度对电子吸收功率及电流驱动效率的影响,结果显示快波能传播到托卡马克等离子体的中心区域并被电子吸收;快波频率对电子吸收快波功率有显著的影响,在70～100 MHz波频率范围内电子对快波吸收效果较好,能有效驱动电流;另外在该频段内随着等离子体温度的升高,电子吸收效果变差。     

阳极结构对直流非转移型等离子体射流特性的影响

本文介绍了自行研制的直流非转移弧等离子体炬的结构和工作原理,研究了不同阳极结构等离子体射流的特性与气体流量、弧功率的关系,以及侧向垂直送气对射流形貌的影响.结果表明,阳极结构对等离子体射流特性的影响较大,弧压随着阳极压缩角的增大而下降,较小压缩角的射流稳定性更好;通道直径较小的等离子体射流刚性更强;不同阳极结构的等离子体炬可以有不同的应用领域.     

轴向磁场中电弧螺旋不稳定性的简化数值分析

在静电近似下，通过数量级的分析，简化了能量方程。用数值方法研究了外加轴向磁场，电流分布、弧电流等对电弧曙旋不稳定性的影响。数值结果表明，在具有外加磁场情况下，当弧柱内均匀电流分布时，正向磁场能够使短波长的扰动稳定，反向磁场能够使长波长的扰动稳定。当弧柱内电流为抛物线形分布时，外加正向磁场对于短波情况下的稳定性影响很小，但对于长波情况，稳定性增强，外加反向磁场，同样能稳定中等和长波情况下的电弧。     

样条配置法解撕裂模方程

采用样条配置法数值求解环流器等离子体撕裂模方程。文中详细介绍了样条配置法的数学方法,并计算了m>1撕裂模稳定的等离子体电流剖面,拟合了HL-1托卡马克装置低q实验的电流剖面。     

样条配置法解撕裂模方程

采用样条配置法数值求解环流器等离子体撕裂模方程。文中详细介绍了样条配置法的数学方法,并计算了m>1撕裂模稳定的等离子体电流剖面,拟合了HL-1托卡马克装置低q实验的电流剖面。     

环形狭缝通道内环状流模型的数值分析

对环形狭缝通道内的环状流建立了分离流模型。应用质量、动量和能量守恒方程 ,加上相应的边界条件和使方程组封闭的经验关系式 ,对环形狭缝通道的内、外液膜厚度、液膜内的速度分布和温度分布 ,以及内、外管的换热系数进行了数值计算求解     

Comparative analysis of the arc characteristics inside the converging-diverging and cylindrical plasma torches

A two-temperature thermal non-equilibrium model is used to simulate and compare the arc characteristics within the converging-diverging and traditional cylindrical plasma torches.The modeling results show that the presence of the constrictor within the converging-diverging torch makes the evolution characteristics of the arc significantly different from that of cylindrical torch.Compared with a cylindrical geometrical torch,a much higher plasma flow velocity and relatively longer high temperature region can be generated and maintained inside the converging-diverging torch.In the constrictor of converging-diverging torch,the normalized radius of arc column increases and the degree of thermodynamic equilibrium of the plasma is significantly improved with the increase of axial distance.The radial momentum balance analysis shows that for the cylindrical torch,the pressure gradient that drives the arc expansion and the Lorentz force that drives the arc contraction dominate the radial evolution of the arc.While at the converging and constrictor region of a converging-diverging plasma torch,the radial gas dynamic forces in arc fringes pointing toward the arc center enhance the mixing of the cold gas of boundary layer with the high temperature gas of the arc center,increasing the average gas temperature and decreasing the thickness of cold boundary layer,thereby facilitating the formation of diffusion type arc anode attachment at the diverging section of torch.     

Three-dimensional non-equilibrium modeling of a DC multi-cathode arc plasma torch

In this paper, a three-dimensional non-equilibrium steady arc model is used to investigate the temperature, velocity and electromagnetic field in multi-cathode arc torch, and the formation mechanism of a large-area, uniform and diffused arc plasma is analyzed. The numerical simulation results show that a large volume plasma region can be formed in the central region of the generator during discharge. During this process, the maximum electron temperature appears near the cathode and in the central convergence region, while the maximum heavy particle temperature only appears in the central convergence region. This phenomenon is consistent with the experimental arc images. Near the cathode tip, the arc column is in a contraction state. In the area slightly away from the cathode, the six arc columns begin to join together. In the plasma generator, there is a large-scale current distribution in all directions of X, Y and Z, forming a stable arc plasma with a wide range of diffusion. The calculated electron temperature distribution is in good agreement with the measured electron temperature. The results suggest that the largearea diffused arc plasma in the multi-cathode arc torch is the combined effect of current distribution, convection heat transfer and heat conduction.     

Characteristics of Plasma Spraying Torch with a Hollow Cathode

1. IntroductionPlasma spraying has became a welLestablishedand widely-used technology with various industrialapplications[1,2,3]. In traditional plasma sprating,the design of plasma torch has been essentially thesame, based on producing a plasma jet by a dc arcopersted between a stick-type cathode and a nozzleshaped anode[4,5]. The powder is injected radiallyillto the plasma flame either within the anode channel or a short distance from the anode. With radialinjection of powders the heating a…     

Effects of inter-electrode insertion on the performance and thermal flow fields of a hollow-electrode plasma torch

The effects of inter-electrode insertion on the performance of a hollow-electrode plasma torch have been investigated by numerical analysis. Simulation results revealed that when inter-electrodes are inserted, the arc voltages and plasma powers increase due to the increase in the arc length. In addition,it was predicted that thermal efficiency can be improved with the increase in plasma power by injecting plasma gases through the gaps between inter-electrodes. These unique effects of inter-electrode insertion are a result of the plasma temperatures adjusting themselves to increase arc voltages when the arc column is contracted radially by increasing gas-flow rate or decreasing inter-electrode diameter.     

Study on the ignition process of a segmented plasma torch

Direct current plasma torches have been applied to generate unique sources of thermal energy in many industrial applications.Nevertheless,the successful ignition of a plasma torch is the key process to generate the unique source (plasma jet).However,there has been little study on the underlying mechanism of this key process.A thorough understanding of the ignition process of a plasma torch will be helpful for optimizing the design of the plasma torch structure and selection of the ignition parameters to prolong the service life of the ignition module.Thus,in this paper,the ignition process of a segmented plasma torch (SPT) is theoretically and experimentally modeled and analyzed.Corresponding electrical models of different stages of the ignition process are set up and used to derive the electrical parameters,e.g.the variations of the arc voltage and arc current between the cathode and anode.In addition,the experiments with different ignition parameters on a home-made SPT have been conducted.At the same time,the variations of the arc voltage and arc current have been measured,and used to verify the ones derived in theory and to determine the optimal ignition parameters for a particular SPT.     

Numerical Simulation of Fluid Flow and Heat Transfer in a DC Non-Transferred Arc Plasma Torch Operating Under Laminar and Turbulent Conditions

In this work, a magnetic fluid dynamics (MHD) model is used to simulate the electromagnetic field, heat transfer and fluid flow in a DC non-transferred arc plasma torch under laminar and turbulent conditions. The electric current density, temperature and velocity distributions in the torch are obtained through the coupled iterative calculation about the electromagnetic equations described in a magnetic vector potential format and the modified fluid dynamics equations. The fluid-solid coupled calculation method is applied to guarantee the continuity of the electric current and heat transfer at the interface between the electrodes and fluid. The predicted location of the anodic arc root attachment and the arc voltage of the torch are consistent with corresponding experimental results. Through a specific analysis of the influence of mass flow rates and electric current on the torch outlet parameters, the total thermal efficiency, thermal loss of each part, and the laws of the variation of outlet parameters with the variation of mass flow rates and electric current was obtained. It is found that operation under a laminar condition with a limited area of the anode could increase the total thermal efficiency of the torch.     

Numerical investigation on the flow characteristics of a reverse-polarity plasma torch by two-temperature thermal non-equilibrium modelling

A two-temperature(2 T) thermal non-equilibrium model is developed to address the thermal nonequilibrium phenomenon that inevitably exists in the reverse-polarity plasma torch(RPT) and applied to numerically investigate the plasma flow characteristics inside and outside the RPT.Then, a detailed comparison of the results of the 2 T model with those of the local thermal equilibrium(LTE) model is presented. Furthermore, the temperature of the plasma jet generated by a RPT and the RPT's voltage are experimentally measured to compare and validate the result obtained by different models. The differences of the measured excitation temperature and the arc voltage between the 2 T model and experimental measurement are less than 13% and 8%,respectively, in all operating cases, validating the effectiveness of the 2 T model. The LTE model overestimates the velocity and temperature distribution of the RPT and its plasma jet, showing that thermal non-equilibrium phenomena cannot be neglected in the numerical modelling of the RPT. Unlike other common hot cathode plasma torches, the thermal non-equilibrium phenomenon is found even in the arc core of the RPT, due to the strong cooling effect caused by the big gas flow rate.     

Study of double-chamber air arc plasma torch and the application in solid-waste disposal

Arc plasma can be applied in hazardous solid waste disposal for higher temperature than common heating methods, but some practical issues exist in practical engineering application. In this study, an air arc plasma torch with double chambers and magnetic controlling is designed to realize wide variable power and long electrode life. The detailed characteristics and laws of the air arc are studied. The condition parameters of arc current(I), air flow rate(G) and the structure parameters of inlet area ratios and electrode diameters influence both the arc voltage and arc root positions. The arc rotating driven by magnetic field effectively lengthens the electrode life. The gasification process and product of organic wastes by air plasma are influenced largely by the waste compositions and the air flow rate. A furnace structure with more even atmosphere and longer residence time should be considered for better gasification. Oxygen-deficient environment is important to suppress NOxformation during the application of air plasma. Inorganic solid wastes can be melt by the air plasma and cooled down to form compact vitreous structures in which heavy metals can be locked and the leaching rates significantly decrease down.     

Design and characteristics of a new type laminar plasma torch for materials processing

Laminar plasma jet(LPJ) generated by laminar plasma torch(LPT) has a favorable temperature and velocity distribution. Thus, it is superior to the turbulent plasma jet in material processing.However, most of the reported LPTs usually operate at a relatively low output power with a relatively low arc voltage and thermal efficiency, which limits its capabilities. In this context, this paper attempts to design a new type of high-power LPT with a relatively low arc current and a high thermal efficiency. In the first section, the design principle of the main components is studied and discussed in detail, and a new high-power LPT is proposed. Then, the experimental characteristics of the proposed high-power LPT are examined. Experimental results reveal the following characteristics of the proposed LPT.(1) The max jet length of the proposed LPT reaches at 540 mm.(2) Its mean arc voltage is higher than 290 V when the LPT works with arc currents lower than 200 A, leading to an output power greater than 50 kW.(3) The mean thermal efficiency is higher than 50%. Lastly, the proposed LPT has been applied to spheroidize the aluminum oxide powers. The experiment results for the production of spherical powders show that the proposed LPT has a good characteristic for material processing.     

Decomposition of Nitrogen Trifluoride Using Low Power Arc Plasma

The low power arc plasma is characterized by extremely high enthalpy and temperature and it is easy to generate and control,and thus thermal decomposition process based on the plasma torch is receiving a great attention for decomposing non-degradable greenhouse gases.In order to elevate the economic feasibility,the efects of input power,waste gas flow rate and additive gases on the destruction and removal efciency(DRE) of NF3 are examined.Specific energy density(SED) deceases as the flow rate increases,and accordingly,the DRE is reduced.The DRE is basically determined by the specific energy density.The highest DRE of NF3 was 97% for the waste gas flow rate of 100 L/min at a low input power level of 2 kW with the help of hydrogen additional gas.The inlet and outlet concentration of NF3 was analyzed using Fourier transform infrared spectroscopy(FT-IR) for DRE of NF3 evaluation.As a result,large amount of NF3 can be efciently decomposed by low power arc plasma systems.