H_(2)O体积分数对纳秒脉冲氮气DBD均匀性的影响

Effect of H_(2)O Volume Fraction on the Uniformity of Nanosecond Pulsed N2 DBD

为产生均匀且高活性的大气压低温等离子体,提高介质阻挡放电(dielectric barrier discharge,DBD)的应用效果,利用纳秒脉冲电源激励氮气DBD,并添加H_(2)O提高等离子体活性。通过电学和光学方法诊断研究了H_(2)O体积分数对氮气DBD特性的影响。利用灰度分析方法和等效电路模型定量分析放电图像和电压电流波形,得到放电均匀性和电学微观参数,计算N_(2)和N_(2)^(+)激发态粒子谱线强度比值来表征约化场强E/n的变化趋势。结果表明:由于H_(2)O的电离反应与H_(2)O吸附电子之间的竞争机制,在氮气DBD中添加H_(2)O体积分数在0到0.6%时,放电均匀性较好,进一步添加H_(2)O后,气隙出现微弱细丝,放电无法充满整个空间,放电均匀性变差。随H_(2)O体积分数增加,传输电荷、平均功率、能量效率、羟基自由基·OH谱线强度以及E/n均先增大后减小,并在H_(2)O体积分数为0.1%时到达最大值。此研究结果有利于制备均匀、稳定且高活性的大气压等离子体源。

In order to produce uniform and reactive plasma and improve the application effect of dielectric barrier dis-charge(DBD),a nanosecond pulse power supply is used to excite N_(2)DBD to achieve large-area homogeneous discharge,and H_(2)O is added to improve the plasma activity.The effects of H_(2)O volume fraction on the discharge characteristics of N_(2)DBD are studied by electrical and optical diagnosis.The discharge image and voltage and current waveform are quan-titatively analyzed by the gray value standard deviation method and equivalent circuit model to obtain the discharge uniformity and electrical parameters,and the change trend of reduced field strength(E/n)is characterized by calculating the ratio of spectral line intensity of N_(2)and N_(2)^(+)excited state particles.The results show that,due to the competition mechanism between the ionization reaction of H_(2)O and the electrons adsorption by H_(2)O when the volume fraction of H_(2)O is 0%to 0.6%in N_(2)/H_(2)O DBD,the discharge stays in good uniformity.After further adding H_(2)O,weak filaments appear in the gap,the discharge cannot fill the entire space,and the discharge uniformity decreases.With the increase of H_(2)O volume fraction,all the transmitted charge,averaged power,energy efficiency,•OH line intensity,and E/n will increase first and then decrease,and reach the maximum value when the H_(2)O volume fraction is 0.1%.The results are conducive to the preparation of homogeneous,stable and highly active plasma sources at atmospheric pressure.