大气压直流双阳极等离子弧脉动特性研究

Arc Fluctuations in a Double Anode Plasma Torch at Atmospheric Pressure

等离子弧的脉动特性是表征等离子体物理状态和过程的重要参数之一,等离子体射流的非稳定性和阳极斑点在电极上的运动是引起等离子弧脉动的主要原因,是等离子体技术的实际应用和进一步发展的关键。该文介绍了一种大气压直流双阳极等离子发生器,通过对等离子弧电信号进行时域和频域分析,研究了载气成分、载气流量和弧电流等参数的变化对等离子弧脉动特性的影响,结果表明在文中的实验条件下等离子弧的伏安特性呈上升趋势,纯氩气作为载气时等离子弧的脉动特性主要和电源的交流分量有关,氩氮混合气体作为载气时等离子弧的脉动特性除了和电源的交流分量有关,还和弧室内存在的赫姆霍茨共振有关,其共振频率独立于气体流量和弧电流的变化。

Plasma arc fluctuation is one of the most important parameters to describe the basic phenomena and processes of plasma source. The major factors to the plasma arc fluctuations are currently identified as the arc root motion on the electrodes and the fluid dynamic instabilities in the plasma jet. Therefore to obtain a comprehensive understanding of the arc dynamic behavior is necessary and indispensable for the effective application and further development of plasma technology. In this paper, a novel DC double arc plasma at atmospheric pressure which provides a long-time and highly stable plasma jet is presented. Current-Voltage characteristic of DC double arc plasma operating with argon and argon-nitrogen mixture was discussed. Arc fluctuations were studied with different operating parameters through time-series and frequency-series analysis of electrical signals in arc plasma. The results show that the takeover mode is characteristic of argon arc and the restrike mode is typical for argon-nitrogen mixture arc. Argon arc fluctuations are mainly induced by the properties of power while the fluctuation of argon-nitrogen arc plasma can be ascribed to the acoustic waves in the region of the first anode attachment. The value of this frequency which is independent of the arc current and the gas flow.