石墨电极气体开关中等离子体弧区碳氧反应效率研究

氧气是石墨电极气体开关中必不可少的组分，用于氧化石墨电极在高温电弧冲击下形成的石墨蒸汽，防止熄弧后石墨蒸汽凝华成固体粉末给开关带来绝缘危害。为提高石墨蒸汽的氧化比例，研究了背景气体组分和氧气浓度对石墨氧化反应的影响，选取3种气体N₂，Ar，He作为背景气体，研究不同气氛电弧的氧化反应特征；在传统的类空气气体（80%的N₂＋20%的O₂）的基础上，提高氧气浓度至40%和60%，研究氧气浓度对碳质氧化比例的改善作用。基于不同气体组分的热力学参数和输运系数，通过电弧磁流体动力学计算模型得到开关温度特征，将电弧与电极界面的热流强度作为石墨电极质量损失速率的评估依据。实验结果表明，随着氧气浓度的升高，石墨蒸汽的氧化比例逐步提高，但当氧气浓度高于40%时，存在电弧引燃石墨电极的风险。当氧气浓度恒定20%时，以Ar作为背景气体时石墨电极质量损失速率较小，且碳蒸汽在电弧中氧化更加充分。因此，相比于传统的开关气体介质，将背景气体替换为Ar或将氧气浓度提高至约40%均能提升碳氧反应效率，降低开关中的杂质残余量。

Research on plasma arc oxidation efficiency of spark gap switch with graphite electrodes

Oxygen is a kind of indispensable component in graphite-electrode spark-gap switch, and it is used to oxidize the graphite vapor formed by the graphite electrode under the impact of high-temperature arcs to prevent the graphite vapor from condensing into solid powder after the arc is extinguished, thus to avoid damage to the switch. To increase the oxidation ratio of the graphite vapor, the influence of background gas composition and oxygen concentration on graphite oxidation reaction is studied in this paper. The effect of dilution gases N₂, Ar, and He on characteristics of the oxidation reaction are studied. Meanwhile, on the basis of the traditional air-like gas (80%N₂＋20%O₂), the carbon oxidation ratio in the case with 40% and 60% oxygen concentration are studied. According to the thermodynamic parameters and transport coefficients of different gases, the arc temperature characteristics are obtained through the magnetohydrodynamic calculation. The thermal energy intensity at the interface between the arc and the electrode is used as the basis for evaluating the mass loss rate of the graphite electrode. Experimental results show that as the oxygen concentration increases, the oxidation ratio of graphite vapor gradually increases. However when the oxygen concentration is higher than 40%, there is a risk of combustion of the graphite electrode. When the oxygen concentration is kept at 20%, the mass-loss rate of the electrode is smaller when Ar is used as the dilution gas, and the carbon vapor is oxidized more fully in the arc. This indicates that compared with the traditional insulation gas, replacing the dilution gas with Ar or increasing the oxygen concentration to around 40% can both improve the carbon-oxygen reaction efficiency and reduce the residual carbon impurities of the graphite-electrode spark-gap switch.