中红外层析吸收光谱技术应用于甲烷掺氨层流预混火焰温度测量

Temperature measurement in methane-ammonia co-fired laminar premixed flame using mid-infrared laser absorption tomography

氨(NH3)是一种代表性的零碳燃料,其完全燃烧产物为水(H_(2)O(g))和氮气。由于其独特的零碳排放优势,近年来,NH3已在热力锅炉、内燃机和工业窑炉中实现高比例掺烧的减排应用。由于火焰温度与燃烧效率和污染物生成密切相关,因此亟须精准的实验数据以实现对燃烧过程的主动控制。本文开发了基于中红外层析吸收光谱技术的测量系统,通过跃迁谱线分析,优选了H_(2)O在基频谱带(v3)内2482 nm附近的吸收谱线开展吸收光谱测量。采用多个Voigt线型函数实现H_(2)O光谱重叠吸收特征的精确拟合,并结合阿贝尔逆变换和正则化技术实现了不同掺氨比燃烧工况下火焰温度的免标定、定量测量。实验结果表明纯氨燃料和甲烷/氨气混合燃料的火焰面位置位于燃烧器上方高度的0.5~2 mm之间,当体积掺氨比从20%向100%增大时,火焰面逐渐远离燃烧器,同时火焰最高温度大约从1600 K上升至2000 K。本文开发的测量方法与系统,不仅能捕捉到层流预混火焰沿着轴向和径向的非均匀温度分布,还能分辨出不同燃烧工况下的火焰温度差异,特别适合零碳氨燃料火焰温度测量。

Ammonia(NH3)is a representative carbon-free fuel,with its primary combustion products being water and nitrogen gas.Due to its unique advantage of zero carbon emissions,high proportions of ammonia co-firing strategy have been successfully implemented in decarbonization of thermal power boilers,internal combustion engines,and industrial furnace.As flame temperature is closely related to combustion efficiency and pollutant generation,it necessitates precise measurements for active control of low-pollution combustion processes.This paper presented the development of a measurement system based on mid-infrared tomographic absorption spectroscopy.By comprehensive analysis of absorption lines,we optimized the selection of absorption lines and finally selected the transitions near 2482 nm within the fundamental band(v3)of H_(2)O.By employing the multiple Voigt profile function,we achieved accurate fitting of the overlapping absorption features of H_(2)O spectra.Combining Abel inversion and regularization techniques,we realized calibration-free and quantitative measurements of flame temperature under different proportions of ammonia blending.The experimental results indicate that the flame sheet positions are located between 0.5 and 2 mm above the burner for pure ammonia flame and methane/ammonia co-fire flame.As the proportion of ammonia increases from 20%to 100%,the flame sheet gradually moves away from the burner,while the maximum flame temperature rises from approximately 1600 K to 2000 K.The proposed measurement technique and system developed in this study not only capture the non-uniform temperature distribution of laminar premixed flames along the axial and radial directions but also discern subtle differences in flame temperature under various combustion conditions.This system is particularly suitable for measuring the flame temperature of zero-carbon ammonia fuels.