氮氣介電質放電的一維數值模擬

Abstract

本論文提出使用一維流體模型模擬氮氣介電質放電，使用平行化的流體模型來模擬純氮氣電漿。流體模型中所有的方程式都是使用牛頓-克雷洛夫-施瓦茲(Newton-Krylov-Schwarz)演算法離散，並搭配單一重疊的施瓦茲preconditioner和線性化矩陣的疊代方法GMRES來求解。 電子能量分布函數可從一套免費的軟體BOLSIG計算得出，計算所需的反應截面積需由使用者輸入，氮氣電漿中所有的傳輸係數和化學反應速率係數都可從電子能量分布函數算出，並且使用一個化學的模組來處理流體模型中化學反應的部分，氮氣電漿在本論文中，總共考慮八種粒子，分別是電子,N2, N2(A3), N2(B3), N2(C3), N2(a’1), N2+, N4+，並考慮30個化學反應式，其中涵括了激發、電離、重組的反應。 討論氮氣電漿模擬的結果，並比較實驗與模擬得到的電流，可看出實驗與模擬的結果相符合，計算各帶電粒子吸收的能量可發現，離子較電子吸收了更多的能量。由模擬得到的密度分度可看出，本提審論文模擬的氮氣放電屬於Townsend-like discharge。此外，也討論不同的介電質常數與不同放電區域大小對電漿的影響。

A simulation of low temperature nitrogen dielectric barrier discharge (DBD) at atmosphere pressure is proposed in this thesis. The parallelized fluid modeling is used to simulate the pure nitrogen discharge. All of the model equations are discretized using fully coupled Newton-Krylov-Schwarz algorithm, in which the preconditioner and linear matrix solver are overlapping additive Schwarz method and Bi-CGStb/GMRES scheme. The transport coefficients of nitrogen plasma and chemical reaction rate are obtained from BOLSIG, which is a Boltzmann solver can evaluate electron energy distribution function by the user given cross sections. A chemistry module take care the reactions in fluid modeling, in which pure nitrogen chemistry in this thesis include 8 species, N2, N2(A3), N2(B3), N2(C3), N2(a’1), N2+, N4+ and electron. 30 reaction channels are considered which include excitation, ionization and recombination reactions. The total currents of simulation and experiment are compared, and it reveals that the simulation result is corresponding to the experiment data. The power absorption is evaluated, and it shows that the absorbed power of ions is higher than the electron. According to the number densities of electron and positive ions simulated, it shows that the discharge is Townsend-like discharge. Furthermore, the influence of different dielectric permittivity and different discharge gap are discussed.