Numerical Simulation of the Ionic Composition and Ionization Phenomena in the Positive Column of a Millisecond DC-Pulsed Glow-Type Discharge in Atmospheric Pressure Air with a Water-Cathode

IF 2.6 3区物理与天体物理 Q3 ENGINEERING, CHEMICAL

Plasma Chemistry and Plasma Processing Pub Date : 2024-08-11 DOI:10.1007/s11090-024-10496-2

M. G. Ferreyra, E. Cejas, B. Santamaría, J. C. Chamorro, B. J. Goméz, L. Prevosto

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Abstract

A numerical investigation of a glow-type discharge in humid air with a water-cathode is reported. A complete block of chemical reactions that self-consistently describes the ionic composition of the plasma is considered. A water molar fraction up to 20% is examined. The electric field strength, emission discharge radius, as well as the OH (A → X) band emission in the positive column was also measured for discharge currents up to 155 mA. The model shows a non-thermal plasma with lower gas temperatures (around 3500 K) than those typically obtained in similar discharges but operating with metal electrodes in dry air. The gas temperature is almost unaffected by the discharge current. The vibrational relaxation through N₂–H₂O collisions is the main gas heating mechanism. The thermal diffusion due to enhanced thermal conductivity by water vapor is the primary cooling mechanism. The electron temperature is around 1 eV to ensure that the electron losses (mainly by dissociative recombination of NO⁺) are compensated by ionization phenomena. The NO⁺ is the dominant ion, mainly formed by electron-impact ionization of NO molecules. An electron number density close to 10¹⁹ m⁻³ is obtained. For the upper water fraction, the electron-impact ionization of O₂ molecules, followed by a quick conversion to NO⁺, also plays a role. The concentration of OH is ~ 10²² m⁻³. A comparison between the model results and the experimental data suggests that the molar fraction of water in the plasma is around 20% for the conditions considered.

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带水阴极的大气压空气中毫秒直流脉冲辉光型放电正柱中离子成分和电离现象的数值模拟

报告对潮湿空气中带有水阴极的辉光型放电进行了数值研究。研究考虑了自洽地描述等离子体离子组成的一整套化学反应。研究了水摩尔分数高达 20% 的情况。还测量了放电电流高达 155 mA 时的电场强度、发射放电半径以及正柱中的 OH（A → X）带发射。该模型显示了一种非热等离子体，其气体温度（约 3500 K）低于在干燥空气中使用金属电极进行类似放电时通常获得的温度。气体温度几乎不受放电电流的影响。通过 N2-H2O 碰撞产生的振动弛豫是主要的气体加热机制。水蒸气增强导热性所导致的热扩散是主要的冷却机制。电子温度约为 1 eV，以确保电子损失（主要是 NO+ 的离解重组）由电离现象补偿。NO+ 是主要离子，主要由 NO 分子的电子撞击电离形成。电子数密度接近 1019 m-3。对于水的上层部分，O2 分子的电子碰撞电离也起了作用，随后迅速转化为 NO+。OH 的浓度约为 1022 m-3。模型结果与实验数据的比较表明，在所考虑的条件下，等离子体中水的摩尔分数约为 20%。

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来源期刊

Plasma Chemistry and Plasma Processing 工程技术-工程：化工

CiteScore

5.90

自引率

8.30%

发文量

审稿时长

6-12 weeks

期刊介绍： Publishing original papers on fundamental and applied research in plasma chemistry and plasma processing, the scope of this journal includes processing plasmas ranging from non-thermal plasmas to thermal plasmas, and fundamental plasma studies as well as studies of specific plasma applications. Such applications include but are not limited to plasma catalysis, environmental processing including treatment of liquids and gases, biological applications of plasmas including plasma medicine and agriculture, surface modification and deposition, powder and nanostructure synthesis, energy applications including plasma combustion and reforming, resource recovery, coupling of plasmas and electrochemistry, and plasma etching. Studies of chemical kinetics in plasmas, and the interactions of plasmas with surfaces are also solicited. It is essential that submissions include substantial consideration of the role of the plasma, for example, the relevant plasma chemistry, plasma physics or plasma–surface interactions; manuscripts that consider solely the properties of materials or substances processed using a plasma are not within the journal’s scope.