扩散电弧等离子体的产生及机制研究

Being the self-contractive effect, atmospheric arc plasma has not been practically large-scale applied in material processing and manufacturing, for its smaller area and greater gradient parameters and etc. So dose a kind of diffused, large area homogeneous arc plasma generated by magnetically rotating arc, which is contributed to "flow control mechanism", for there exists the strong radial flow towards the electrode. To meet the application, making exploration of a new mechanism and control methods of generating diffusive arc plasma is of both significant academic value and a wide range of application background. By experimental research, theoretical calculation and numerical simulation, the project intends to study laws of coupling process of "electric-magnetic-heat-flow" fields in the arc plasma, and their effects on arc plasma diffusion, to do various boundary conditions effects on arc plasma diffusion, including electrodes' configuration and temperature/currents, heat and flow of the generator wall, and etc. So that new mechanisms on arc diffusion would be understood explored. Research contents include: (1) Calculating transport properties of the non-equilibrium plasma of single atom molecules and their composition, propose an appropriate gas composition for the diffused arc purpose. (2) Design a simulating experimental device to produce the diffused arc plasma. (3) Building a self-consistent model of coupling "electrodes-boundary layer-NLTE plasma". (4) On this experimental device, experimental and numerical simulation researches on: the coupling laws of "electric-magnetic-thermal-flow" field in the diffused arc plasma configuration, the effects on the arc plasma diffusion and its uniformity as well as stability by the characteristics of the gases, the heat and flow boundary conditions of the generator, the boundary conditions of the electrodes and etc. Based on above researches, the control conditions of the diffusive arc plasma configuration would be analyzed and the preliminary design of the diffusive arc plasma generator is proposed. The above work will lay a preliminary foundation for the development of a new type of arc plasma source.

电弧等离子体具有自收缩的位形特点，是其大规模用于材料加工和处理的瓶颈。磁旋转电弧通过"流动控制机制"产生扩散电弧等离子体，但存在极强的朝向电极的流动，是其应用于材料加工的障碍。从应用出发，探索产生扩散电弧等离子体的新机制和控制方法，兼具重要的学术价值和广泛的应用背景。本项目研究内容包括：建立研究电弧扩散/收缩的物理数学模型，计算各种气体非平衡等离子体输运性质，分析提出有利于电弧扩散的气体或组成组成；建立完善耦合"电极-电极边界层-NLTE等离子体"的自洽模型，设计扩散电弧等离子体炬和多阴极扩散弧等离子体的模拟实验装置：实验和数值模拟研究扩散电弧等离子体位形中"电-磁-热-流"耦合作用规律，研究气体性质、发生器边界热流条件、电极边界条件等对等离子体扩散程度、等离子体分布均匀和稳定性的影响，分析扩散电弧等离子体位形产生的控制条件，产生扩散电弧等离子体。

大气压电弧具有自收缩效应，使电弧等离子体存在体积小、参数梯度大、能量高度集中等特点，限制了其在材料制备、大面积表面处理等领域的应用。从应用出发，探索产生扩散电弧等离子体的新机制和控制方法，兼具重要的学术价值和广泛的应用背景。本项目基于“E-H”能量方程，理论分析影响等离子体收缩/扩散的输运性质，建立由传热主导能量输运的弧柱收缩/扩散模型；建立完善“耦合电极-电极边界层-NLTE等离子体的自洽模型”，设计多阴极扩散电弧等离子体发生器和磁旋转电弧等离子体发生器的模拟实验装置，通过实验和数值模拟研究扩散电弧等离子体位形中“电-磁-热-流”耦合作用规律，研究气体性质、发生器边界热流条件、电极边界条件等对等离子体扩散程度、等离子体分布均匀和稳定性的影响，分析扩散电弧等离子体位形产生的控制条件。主要研究结果如下：①证明了Steenbeck“最小弧压原理”的错误，并从能量的角度出发推导了弧柱扩散的有利条件：当等离子体中电子传热占主导时，有利于弧柱扩散；当等离子体中重粒子传热占主导时，弧柱趋于收缩。据此可以得到不同气体组分下电弧的扩散程度。②发展的“电极-电极边界层-NLTE等离子体的自洽模型”成功预测了收缩、扩散弧根模式，揭示了弧柱、近电极区和电极之间的能量输运过程，显示弧根形态和弧柱形态互相影响。③设计了多阴极扩散电弧等离子体发生器和磁旋转等离子体发生器，产生了稳定扩散电弧等离子体，部分验证了扩散电弧理论。④利用扩散电弧等离子体机理，产生了大截面、放电稳定的等离子体源，并产生稳定的长层流射流等特点，初步探索其在等离子喷涂、粉体球化等领域的应用。