Fluid Modeling of Parallel-plate Nitrogen-based Dielectric Barrier Discharge Driven by a Realistic Distorted Sinusoidal AC Power Source

• Main Authors: Cheng, Kai-Wen, 鄭凱文
• Other Authors: Wu, Jong-Shinn
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/41305367643574371560

博士 === 國立交通大學 === 機械工程學系 === 100 === A simulation of parallel-plate dielectric barrier discharge (DBD) using pure nitrogen and N2/O2 gas driven by a realistic distorted-sinusoidal voltage power source (60 kHz) is studied. The simulated current-voltage characteristic results quantitatively agree with experimental measurements. In the pure nitrogen simulations, N4+ ion density is the dominant charged species, which is unlike most glow discharges. The discharge transforms from Townsend-like to filamentary-like (microdischarge) as gap distance is more than 1.0 mm, which was also observed in the experiment. All densities of charged and neutral species increase exponentially with increasing applied peak voltages in the range of 6.2-8.6 kV. The higher permittivity of the dielectric material is, the larger the discharge current and the longer the period of gas breakdown are. In addition, the quantity of accumulated charge at each electrode increases with increasing permittivity of the dielectric material. Finally, the increase of dielectric thickness from 1.0 to 2.0 mm greatly reduces the densities of all species and also the plasma absorbed power. When trace amount of oxygen is introduced in nitrogen plasma, the dominate charged species are N4+ and O2- with densities about 1018 m-3. The neutral species densities of and atomic nitrogen are approximately 4 × 1019 m-3 and 1 × 1021 m-3 respectively, which agree well with experiments. The oxygen addition can significantly decrease the electron density from the order of 1017 m-3 down to 1014 m-3 as the fraction of trace oxygen increases from 0.003 % to 0.1 %. In addition, the calculated photon radiations are compared against the measured spectra. The spectral bands of second positive system (SPS) of N2, NOγ-system and ON2-excimer are selected for comparison. Results reveal that the simulations and experiments show the similar trend with oxygen addition, in which the quantity of radiation increases rapidly first, peaks at some oxygen addition and then followed by a slow decrease.