基于高光谱技术的甲烷层流预混火焰自由基特性研究

高光谱技术提供了空间和光谱维度的信息，同时基于传统黑体模型的实验技术和计算方法不适用于甲烷火焰的辐射特性，而火焰中自由基的高光谱信息反映了火焰结构、组分浓度分布等燃烧的多方面特征，能够为燃烧模型的完善提供依据。利用高光谱技术在不同当量比和不同流量下研究了甲烷预混火焰中自由基的空间和光谱特性。对不同当量比的研究表明，随着当量比的增加，火焰中心处的CH*和C*₂自由基的辐射强度先增加后降低，而燃烧区域内二者的平均辐射强度一直增加，火焰中心处的点可以表征局部的燃烧状态，而燃烧区域内辐射均值表征热释率等整体燃烧状态，定量给出了两种方法的不同趋势。火焰中心处的CH*自由基辐射强度在当量比为1.01时达到峰值，而C*₂自由基辐射强度在当量比为1.12时达到峰值，两种自由基的辐射峰值可以分别作为燃烧中反应强度和稳定性的判据。当量比可以由C*₂和CH*辐射强度之比来表征，修正了C*₂/CH*和当量比的线性关系，提出应使用燃烧区域内C*₂和CH*的平均辐射强度之比，并提出了该比值与当量比的二次关系。利用高光谱技术生成了燃烧区域内C*₂/CH*的云图，得到了详细的空间信息，当量比大于1时，首次在火焰面附近发现了明显的过渡区，体现了高光谱技术的优势。对当量比保持不变情况下的不同流量的研究表明，随着流量的增加，火焰高度增加，而火焰顶部和火焰中心的自由基的浓度分布基本不发生变化，揭示了实验工况下流动的特征时间远小于化学反应特征时间，化学反应过程未受到明显影响。应用高光谱较好的识别出了火焰中的多种自由基，研究了甲烷层流预混火焰中自由基辐射特性及其随着不同当量比和流量变化的趋势，对燃烧现象和机理的认识具有重要意义。

Study on Radical Characteristics of Methane Laminar Premixed Flame Based on Hyperspectral Technology

Hyperspectral technology provides spatial and spectral dimension information. Meanwhile, the experimental technology and calculation method based on the traditional blackbody model is not suitable for the radiation characteristics of methane flame. The Hyperspectral Information of free radicals in the flame reflects many aspects of combustion characteristics, such as flame structure and component concentration distribution, which can provide a basis for improving the combustion model. This paper studied the spatial and spectral characteristics of free radicals in premixed methane flames by Hyperspectral techniques at different equivalence ratios and flow rates. The study of different equivalence ratios shows that with the increase of equivalence ratios, the radiation intensity of CH* and C*₂ radicals in the center of the flame increases first and then decreases. In contrast, the average radiation intensity of CH* and C*₂ radicals in the combustion region increases all the time. The point in the center of flame can represent the local combustion state. While the average radiation intensity in the combustion region represents the overall combustion state, such as heat release rate, this paper gives the different trends of the two methods quantitatively. The radiation intensity of CH* radical in the center of flame reaches the peak when the equivalence ratio is 1.01, while the radiation intensity of C*₂ radical reaches the peak when the equivalence ratio is 1.12. The radiation peak of the two radicals can be used as the intensity criterion and stability of the reaction in combustion. Equivalence ratio can be expressed by the C*₂ to CH* radiation intensity ratio. This paper corrected the linear relationship between C*₂/CH* and equivalence ratio. It is proposed that the ratio of average radiation intensity of C*₂ and CH* in the combustion zone should be used. The quadratic relationship between the ratio and equivalence ratio is also proposed. The cloud image of C*₂/CH* in the combustion area is generated by hyperspectral technology, and the detailed spatial information is obtained. When the equivalence ratio is greater than 1, an obvious transition zone is found near the flame surface for the first time, which shows the advantages of hyperspectral technology. The study of different flow rates with a constant equivalence ratio shows that the flame height increases with the flow rate increase, while the concentration distribution of free radicals at the top and center of the flame does not change. It reveals that the characteristic time of a flow is far less than that of chemical reaction under experimental conditions, so the chemical reaction process is not affected. In this paper, hyperspectral technology is used to identify a variety of free radicals in the flame. The radiation characteristics of free radicals in methane laminar premixed flame and its variation trend with different equivalence ratios and flow rates are studied, which is of great significance for applying hyperspectral technology to study methane combustion characteristics and verify the reaction mechanism of methane combustion phenomenon.