Investigation of Thermodynamic Conditions in an Arc Discharge Plasma

本研究的目的是提高我们对电弧放电等离子体的基本物理学的认识。等离子体通常被称为物质的第四种状态，它是一种电离气体，几乎存在于日常生活的方方面面；电弧放电是工业上和自然界中观察到的最基本的等离子体现象之一。电弧的例子包括闪电、燃烧用火花塞、等离子火把、用于超音速和高超音速流动的电弧装置，以及用于纳米材料合成的装置。根据其产生和维护的条件，电弧放电等离子体具有广泛的特性和参数，其中许多仍然知之甚少。本研究将使用数值模拟和最先进的激光诊断来扩展对电弧放电的理解。通过该项目将培训下一代等离子体科学家和工程师，同时将提高当地K-12学生对等离子体技术及其重要性的认识。尽管历史悠久，但由于对处于热平衡状态的等离子体的实验测量有限，人们对大气压电弧放电的局部热力学平衡（LTE）条件知之甚少。传统的探针和光学测量带来了巨大的挑战，因为电弧核心是一个高温环境和高强度的辐射。本项目的重点是研究在大气压力下电弧放电中LTE假设的有效性。具体而言，研究目标是：(1)建立非烧蚀氮弧等离子体的多维非平衡等离子体模型，并结合辐射传热模型；（ii）建立等离子体流动相干瑞利-布里渊散射（CRBS）技术的理论和分析；（iii）根据实验数据验证计算结果，包括从CRBS获得的平移温度和从光学发射光谱获得的氮的振动状态。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The goal of this study is to improve our understanding of the basic physics of arc discharge plasmas. Plasma, often called the fourth state of matter, is an ionized gas that is present in almost every aspect of everyday life; and an electric arc discharge is one of the most basic plasma phenomena that are used in industry and observed in nature. Examples of electric arcs include lightning, spark plugs for combustion, plasma torches, arcjet facilities for supersonic and hypersonic flows, and devices for nanomaterials synthesis. Depending on the conditions of their generation and maintenance, arc discharge plasmas have a wide range of properties and parameters, many of which remain poorly understood. This study will be performed using both numerical simulations and state-of-the-art laser diagnostics to expand the understanding of arc discharges. Training the next generation of plasma scientists and engineers will be provided through this project while awareness about plasma technologies and its importance will be raised to local K-12 students.Despite its long history, the conditions for local thermodynamic equilibrium (LTE) in atmospheric pressure arc discharges are poorly understood due to limited experimental measurements of plasmas in thermal equilibrium. Conventional probes and optical measurements pose significant challenges since the arc core is a high temperature environment with high intensity of radiation. The focus of this project is to investigate the validity of the LTE assumption in an arc discharge operating in atmospheric pressure. Specifically, the research objectives are to: (i) develop a multidimensional nonequilibrium plasma model of a non-ablating nitrogen arc plasma coupled with a radiative heat transfer model; (ii) establish theory and analysis of the Coherent Rayleigh-Brillouin Scattering (CRBS) technique for plasma flows; and (iii) validate the computational results against experiment data, including the translational temperature obtained from CRBS and the vibrational state of nitrogen obtained from Optical Emission Spectroscopy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.