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首页> 外文期刊>Journal of Physics, D. Applied Physics: A Europhysics Journal >A collisional-radiative model of iron vapour in a thermal arc plasma
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A collisional-radiative model of iron vapour in a thermal arc plasma

机译：热弧等离子体中铁蒸汽的碰撞模型

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A collisional-radiative model for the ground state and fifty effective excited levels of atomic iron, and one level for singly-ionized iron, is set up for technological plasmas. Attention is focused on the population of excited states of atomic iron as a result of excitation, de-excitation, ionization, recombination and spontaneous emission. Effective rate coefficients for ionization and recombination, required in non-equilibrium plasma transport models, are also obtained. The collisional-radiative model is applied to a thermal arc plasma. Input parameters for the collisional-radiative model are provided by a magnetohydrodynamic simulation of a gas-metal welding arc, in which local thermodynamic equilibrium is assumed and the treatment of the transport of metal vapour is based on combined diffusion coefficients. The results clearly identify the conditions in the arc, under which the atomic state distribution satisfies the Boltzmann distribution, with an excitation temperature equal to the plasma temperature. These conditions are met in the central part of the arc, even though a local temperature minimum occurs here. This provides assurance that diagnostic methods based on local thermodynamic equilibrium, in particular those of optical emission spectroscopy, are reliable here. In contrast, deviations from the equilibrium atomic-state distribution are obtained in the near-electrode and arc fringe regions. As a consequence, the temperatures determined from the ratio of line intensities and number densities obtained from the emission coefficient in these regions are questionable. In this situation, the collisional-radiative model can be used as a diagnostic tool to assist in the interpretation of spectroscopic measurements.
机译：建立了一个碰撞 - 辐射模型，用于地面态和五十次有效的原子铁和单电离铁的一个水平，用于技术等离子体。注意，由于激发，脱离激发，电离，重组和自发排放，关注原子铁的群体。还获得了在非平衡等离子体传输模型中所需的电离和重组的有效率系数。碰撞模型应用于热弧等离子体。集电辐射模型的输入参数由气金属焊接弧的磁性流体模拟提供，其中假设局部热力学平衡并处理金属蒸汽的运输基于组合的扩散系数。结果清楚地识别了电弧中的条件，原子状态分布满足螺栓玻璃场分布，其激励温度等于等离子体温度。这些条件在弧的中央部分满足，即使在此发生局部温度最小。这提供了保证，这里基于局部热力学平衡，特别是光发射光谱的诊断方法在此处可靠。相反，在近电极和弧形边缘区域中获得与平衡原子区分布的偏差。结果，从这些区域中的发射系数获得的线强度和数量密度的比率确定的温度是值得怀疑的。在这种情况下，碰撞模型可以用作诊断工具，以帮助解释光谱测量。

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