Optical temperature measurement in unsteady plasma free jet
Optical temperature measurement in unsteady plasma free jet
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DOI：
10.1088/1361-6501/ad24b7
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发表时间：
2024-01
影响因子：
2.4
通讯作者：
Tobias Hermann;Eric Won Keun Chang
中科院分区：
文献类型：
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作者：
Tobias Hermann;Eric Won Keun Chang
利用光谱窄带滤波高速成像技术对氩等离子体自由射流进行了研究。在16 kHz下以3.9 μs的曝光时间捕获图像，然后校准绝对辐射。自由射流表现出与湍流自由剪切流一致的行为，并保持轴对称形状。随着时间的推移，观察到显着的局部波动，增长的强度和大小的对流下游。假设局部热力学平衡和自相似的自由射流温度分布，流辐射被用来确定局部等离子体温度和射流宽度。然后，定常和非定常流动模型被用来解释射流波动。在喷嘴出口附近的低波动区域，两个模型显示出良好的协议的中心线温度，测量约11 200 K。在显著波动的区域，稳定流的假设导致温度高估32%，射流宽度高估18%，总射流功率高估41%。非定常分析方法导致较低的温度和较小的射流宽度，同时满足动量和能量守恒。
An Argon plasma free jet is investigated using spectrally narrow bandpass filtered high-speed imaging. The images were captured at 16 kHz with an exposure time of 3.9 μs and then calibrated for absolute radiance. The free jet exhibited behaviour consistent with turbulent free shear flow and maintains an axisymmetric shape. Significant local fluctuations were observed over time, growing in strength and size as the flow convected downstream. Assuming local thermodynamic equilibrium and self-similar free-jet temperature profiles, the flow radiance is used to determine the local plasma temperature and the jet width. Then, both steady and unsteady flow models were applied to account for the jet fluctuation. In regions of low fluctuations near the nozzle exit, both models show good agreement for centreline temperatures, measuring approximately 11 200 K. In regions of significant fluctuations, the assumption of steady flow leads to an overestimation of 32% for temperature, 18% for jet width, and 41% for total jet power. The unsteady analysis approach results in lower temperatures and smaller jet widths while simultaneously satisfying momentum and energy conservation.