电弧加热器高温流场激光吸收光谱诊断

摘要

Gas temperature and species number density are the key parameters to quantitatively assess the arc-heated wind tunnel operation and flow quality.Conventional techniques meet great challenge in high enthalpy flow diagnostics for arc-heated facilities under prolonged operation at high temperatures.Based on the local thermodynamic equilibrium plasma assumption, this paper presents in-situ diagnostics for the dissociated air (>5000K) in the arc heater by using laser absorption spectroscopy of atomic oxygen at the wavelength of 777.19nm.The gas temperature and the number density of atomic oxygen are measured under two operation conditions of H0=15.8MJ/kg and 17.4MJ/kg, respectively.The average temperatures are 5843K and 6047K, corresponding to 5950K and 6335K from charts for high temperature equilibrium flow properties of air.The number density of atomic oxygen is within (1.1~1.2)×1018cm-3 and is in consistency with the calculation via NASA-CEA program,while the number density of atomic oxygen (5S02) is within (1.0~1.5)×1010cm-3.This work demonstrates that the laser absorption spectroscopy is applicable for high enthalpy flow diagnostics in the arc-heated wind tunnel as a new technique.%气流温度和组分粒子数密度是定量评估电弧加热器运行参数和流场品质的关键,常规测试手段难以适应电弧加热器内高温气流的恶劣环境,电弧加热器等离子体气流诊断研究一直缺乏有效手段.本研究应用激光吸收光谱技术,选用原子O(777.19nm)谱线, 基于局部热化学平衡等离子体假设,对电弧加热器内高温离解空气(>5000K)试验气流进行在线诊断.试验测得了总焓H0=15.8,17.4MJ/kg 2组工况下,电弧加热器内等离子体气流温度和原子O粒子数密度.2组工况获得平均气流温度分别为5843和6047K,对应高温平衡气流表获得气流温度为5950和6335K.测得加热器运行稳定后2组工况的原子O总粒子数密度在(1.1~1.2)×1018cm-3之间,低能级5S02粒子数密度在(1.0~1.6)×1010cm-3之间,2组工况原子O总粒子数密度的差异与NASA-CEA平衡计算结果一致,验证了电弧加热器气流局部热力学平衡假设的有效性.本研究工作验证了激光吸收光谱技术可作为高焓电弧加热器常规诊断手段.