Effect of H2O Volume Fraction on the Uniformity of Nanosecond Pulsed N2 DBD
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 N2 DBD to achieve large-area homogeneous discharge,and H2O is added to improve the plasma activity.The effects of H2O volume fraction on the discharge characteristics of N2 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 N2 and N2+excited state particles.The results show that,due to the competition mechanism between the ionization reaction of H2O and the electrons adsorption by H2O when the volume fraction of H2O is 0%to 0.6%in N2/H2O DBD,the discharge stays in good uniformity.After further adding H2O,weak filaments appear in the gap,the discharge cannot fill the entire space,and the discharge uniformity decreases.With the increase of H2O 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 H2O volume fraction is 0.1%.The results are conducive to the preparation of homogeneous,stable and highly active plasma sources at atmospheric pressure.
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