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微间隙放电是放电间距和电极尺寸均在亚毫米及以下量级的气体放电形式. 为研究微米间隙放电起始路径及放电过程中粒子密度的变化机理与规律, 本文搭建了大气压下微间隙空气放电实验及放电图像采集装置, 采用COMSOL仿真软件对微间隙空气放电过程中的电子密度、空间电荷分布进行模拟, 并使用MATLAB软件计算微间隙放电的分形维数与概率发展指数. 实验研究在大气压室温下、间隙距离为50—150 μm时, 针尖施加正极性直流电压的空气放电现象. 实验发现, 放电通道存在曲折段, 放电过程中分叉数比长间隙情况少, 原因为放电机制以汤森理论为主, 流注理论为辅, 存在弱流注形式, 放电通道呈曲折和分支状, 但分叉数较少, 曲折度较低. 使用COMSOL模拟得出, 在阴极形成鞘层, 阴极电场畸变为原来的3—8倍, 放电过程中电子密度最高达到2.17 × 10 21m –3. 使用分形理论仿真来模拟微间隙放电, 发现分形维数与电压和间隙距离成正比; 当概率发展指数 η= 1.18—1.3时, 模拟放电过程的分形维数与实验较接近. 本工作为进一步探索亚微米-纳米间隙的放电情况打下了基础.Micro-gap discharge is a form of gas discharge in which the discharge gap is on the order of sub-millimeters orless. To study the initial path of micro-gap discharge and the mechanism and law of particle density change during discharge, in this paper a micro-gap discharge experiment and discharge image acquisition device under atmospheric pressure is built and the COMSOL simulation software is used to simulate the electron density and space charge in the process of micro-gap air discharge. Furthermore, the MATLAB software is used to calculate the fractal dimension and probability development index of micro-gap discharge. The air discharge phenomena produced by applying positive DC voltage to needle tip at atmospheric pressure and room temperature with gap distance ranging from 50 μm to 150 μm are studied. It is found experimentally that there are twists and turns in the discharge channel, and the number of bifurcations in the discharge process with a short gap is less than that with a long gap. Observation of the micro-gap air discharge process with a gap of 100 μm under atmospheric pressure shows that the discharge process is divided into the following three processes: needle tip corona, corona breakdown streamer, and spark discharge channel. Based on the analyses of these experimental results, it can be concluded that the discharge mechanism follows Thomson's theory, supplemented by the streamer theory. The cathode secondary electron emission (including positive ions colliding with the cathode and photoelectron emission) and the space charge distortion electric field form a secondary electron avalanche to maintain the discharge together. The seed electrons formed by a small amount of space photoionization also form an electron avalanche under the action of the space charge distortion electric field. There are tortuous sections in the discharge channel, but the number of branches is small and the degree of tortuosity is low. Therefore, there are weak streamer forms. The discharge channel is tortuous and branched, but the number of bifurcations is relatively small, and the tortuousness is low. In addition, it is also found that a sheath is formed at the cathode, the distortion of electric field is 3–8 times that of original electric field, and the electron density reaches 2 × 10 21m –3during discharge, obtained from the COMSOL simulation. Meanwhile, the fractal theory simulation is used to simulate the micro-gap discharge. In the process of research, the fractal dimension is found to be proportional to the voltage and the gap distance. When the probability development index η= 1.18–1.3, the fractal dimension of the simulated discharge process is closer to the experimental result. The findings in this paper lay the foundation for further exploring the discharge theory of sub-micro- and nano-scaled gaps.
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序号 反应 反应速率常数 R1 e + N2→ e + N2 f(ε) R2 e + N2→ 2e + ${\rm{N}}_2^+ $ f(ε) R3 e + O2→ e + O2 f(ε) R4 e + O2→ 2e + ${\rm{O}}_2^+ $ f(ε) R5 e + O2→ O + O– f(ε) R6 e + ${\rm{O}}_2^+ $ → 2O 2.42×10–13(300/Te) R7 e + ${\rm{O}}_4^+ $ → 2O2 1.4×10–12(300/Te)0.5 R8 e + 2O2→ O2+${\rm{O}}_2^- $ 2×10–41(300/Te) R9 e + ${\rm{N}}_2^+ $ + N2 → 2N2 6.07×10–34$T_{\rm{e}}^{-2.5}$ R10 2e + ${\rm{N}}_2^+ $ → e + N2 5.651×10–27$T_{\rm{e}}^{-0.8}$ R11 ${\rm{N}}_2^+ $ + O2+ N2→ ${\rm{O}}_4^+ $ + O2 5×10–41 R12 ${\rm{N} }_2^+$+ N2+ N2→ ${\rm{N} }_4^+$ + N2 5×10–41 R13 ${\rm{N} }_4^+$ + O2→ ${\rm{O}}_2^+ $ + 2N2 2.5×10–16 R14 ${\rm{N}}_2^+ $ + O2→ ${\rm{O}}_2^+ $ + N2 1.04×10–15$T^{-0.5} $ R15 2N2+ ${\rm{O}}_2^+ $ → N2${\rm{O}}_2^+ $ + N2 8.1×10–38$T^{-2} $ R16 N2+ N2${\rm{O}}_2^+ $ → 2N2+ ${\rm{O}}_2^+ $ 14.6$T^{-5.3} $
exp (–2357/T)R17 O2+ N2${\rm{O}}_2^+ $ → N2+ ${\rm{O}}_4^+ $ 1×10–15 R18 ${\rm{O}}_2^+ $ + O2+ N2→ ${\rm{O}}_4^+ $ + N2 2.04×10–34$T^{-3.2} $ R19 ${\rm{O}}_2^+ $ + O2+ O2→ ${\rm{O}}_4^+ $ + O2 2.04×10–34$T^{-3.2} $ R20 ${\rm{O}}_4^+ $ + ${\rm{O}}_2^- $ → 3O2 1×10–13 R21 ${\rm{O}}_4^+ $+${\rm{O}}_2^- $ + O2→ 3O2+ O2 2×10–37 R22 ${\rm{O}}_4^+ $+${\rm{O}}_2^- $ + N2→ 3O2+N2 2×10–37 R23 ${\rm{O}}_2^+ $ + ${\rm{O}}_2^- $ + O2→ 3O2 2×10–37 R24 ${\rm{O}}_2^+ $+${\rm{O}}_2^- $ + N2→ 2O2+N2 2×10–37 R25 O2+ O + N2→ O3+ N2 2.5×10–46 R26 O2+ O + O2→ O3+ O2 2.5×10–46 R27 ${\rm{O}}_2^+ $ + O–→ O + O2 3.46×10–12$T^{-0.5} $ 注: 反应中二体碰撞的反应速率常数单位为 m3/s; 三体碰撞的反应速率常数单位为 m6/s;Te和T单位为 K, 其中Te为电子温度. 
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仿真次数 η= 1.1 η= 1.15 η= 1.18 η= 1.2 η= 1.3 η= 1.4 1 1.4099 1.4246 1.4013 1.3808 1.3797 1.2969 2 1.4478 1.3906 1.4183 1.3877 1.3808 1.3713 3 1.4683 1.395 1.4428 1.4079 1.384 1.3106 4 1.43 1.47 1.3732 1.4399 1.3656 1.3579 5 1.4592 1.4475 1.4252 1.4031 1.4183 1.3229 6 1.4855 1.3957 1.4609 1.4006 1.3591 1.3846 7 1.4979 1.4283 1.4233 1.4344 1.4001 1.3524 8 1.4985 1.3978 1.4006 1.3764 1.4079 1.3378 9 1.4274 1.4428 1.4381 1.3696 1.4016 1.3179 10 1.4169 1.422 1.3441 1.4155 1.4006 1.3656 均值 1.4541 1.4214 1.4128 1.4016 1.3898 1.3418 95%置信区间 [1.4306 1.4777] [1.4023 1.4405] [1.3881 1.4375] [1.3846 1.4186] [1.3762 1.4034] [1.3210 1.3625] 下载:
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