液体电极上辉光放电丝的运动特性研究

大气压液体电极放电在生物医疗、化学降解、环境保护等众多方面具有广泛的应用前景,引起了研究者的关注.本文利用直流电压激励棒-水电极装置,在6 mm气隙间产生了大气压辉光放电.研究发现,随着电流的增大,放电由锥状转变成柱状,且此过程中水面上放电环的直径先增大后减小.利用高速照相机对放电进行研究,发现锥状放电是由单个放电丝旋转形成的.通过测量放电的伏安特性,表明放电处于正常辉光机理.利用光谱学方法,研究了不同电流下的振动温度、转动温度和谱线强度比I_(391.4)/I_(337.1),发现它们均随电流的增加而增大.根据气体放电理论,分析和解释了放电丝的运动机理,并对水面上放电环直径随电流的变化关系进行了解释.这些结果对于大气压液体电极放电的理论研究和实际应用均具有一定参考价值.

Rotating characteristics of glow discharge filament on liquid electrode surface

Atmospheric pressure glow discharge above liquid electrode has extensive application potentials in biomedicine, chemical degradation,environmental protection,etc.In this paper,such a kind of discharge excited by a direct current voltage is generated through using a metal rod above water surface.Results show that the discharge has a ring shape on the water surface when the current is low.With increasing the discharge current,its diameter first increases,and then decreases after reaching a maximum,and finally slightly increases.In this process,the discharge transits from a conical shape to a column.Fast photography indicates that the conical discharge actually originates from the rotation of a discharge filament,which can be attributed to the effect of electronegative particles generated in the discharge channel. These electronegative particles,mainly including NO,NO₂,NO₃,O,O₃ and OH,can increase electron attachment coefficient β,resulting in extinguishment of the original discharge channel.Due to a similar field value and a normal β coefficient,the breakdown conditions can be satisfied in a region adjacent to the original channel.Therefore,the discharge will move into the new region.Further investigation indicates that both the conical discharge and the column discharge are in a normal glow regime.By optical emission spectroscopy,it is found that the vibrational temperature,the rotational temperature and the intensity ratio of I_391.4/I_337.1 increase with increasing the current.Electron mobility decreases in the conical discharge due to voltage decreasing with the current.Hence,electrons have an increased possibility with which they are attracted by the electronegative particles to form negative ions.Consequently,with increasing the discharge current,more negative ions will be accumulated not only near the conical center,but also in the vicinity of the discharge channel.Obviously,there is repulsive force between the negative ions in the two regions.The repulsive force increases with increasing the discharge current,which leads to the ring diameter increasing with the current.Besides the negative ions,gas temperature plays another important role in the discharge.It increases with current increasing,leading to the decrease of gas density in the discharge channel.Hence,electrons have a reduced probability with which they are attached by electronegative particles.This factor will lead to a reduced force between less negative ions in the two regions.Consequently,after reaching its maximum,the ring diameter decreases with current increasing.If the current is high enough,the discharge channel will have a sufficiently high temperature and an adequately lower gas density, resulting in an increased electron energy as well as an increased α(the first Townsend ionization coefficient).Therefore, the discharge will be self-sustained in the original region,other than move into an adjacent region.Consequently,the column discharge appears with the current increasing to some extent.In the column discharge,more negative ions will be accumulated above the water surface with increasing the current.These negative ions extend along the water surface,which contributes to the slight diameter increase of the luminous column.These experimental results are of great significance for theoretically studying liquid anode discharge.