基于Raman与FTIR对掺甲烷乙烯/氢气扩散火焰碳烟有序度和官能团的研究

以甲烷、乙烯、氢气混合扩散火焰碳烟为研究对象，采用激光共聚焦拉曼光谱（Raman）和傅里叶红外光谱（FTIR）研究了不同掺甲烷比例下乙烯、氢气混合火焰碳烟有序度及官能团的分布特性，分析了碳烟石墨化和官能团分布，揭示了掺甲烷对乙烯/氢气（氢气比例30%）层流扩散火焰的碳烟生成影响规律。Raman研究表明在甲烷掺混比为3%和7%时，在火焰高度低于4cm位置生成的碳烟有序程度显著降低，表明在此区域存在明显的碳烟生成协同效应；甲烷掺混比增大超过10%时，协同效应基本消失，碳烟有序度上升。FTIR研究表明掺混甲烷对碳烟官能团组成影响明显。掺混甲烷后脂肪族官能团相对含量整体提高。随着甲烷掺杂比的增大，CH₂相对含量增大到一峰值后减小。碳烟中芳香族官能团含量随着火焰高度的上升含量下降明显。掺混3%和7%甲烷，芳香族官能团在2和3 cm火焰高度时，芳香族官能团的含量明显上升。掺混甲烷比高于10%时，芳香族官能团的含量则有所降低。表明少量甲烷掺混使得CH₃和C₃H₃生成有了新的途径，CH₃和C₃H₃增加，而C₂H₄和C₂H₂减少不明显，从而促进了多环芳香烃(PAHs)的生成。继续增加甲烷因为稀释作用会抑制C₂H₂生成从而减少PAHs的生成，芳香族相对含量降低，因而降低了碳烟的生成。研究揭示了甲烷对乙烯/氢气层流扩散火焰中碳烟形成的相互作用：在低甲烷掺混比时存在协同效应促进碳烟生成，而在高甲烷掺混比时协同效应消失。

Study on the Soot Order Degree and Functional Groups of Doping CH4 Into C2H4/H2 Diffusion Flame With Raman and FTIR

The soot formation characteristics of mixed diffusion flame of methane doping into ethylene/hydrogen were explored with Laser Confocal Raman spectrum (Raman) and Fourier Transform Infrared Reflection (FTIR), the soot order degree and the functional group’s distribution characteristic in the mixed flame with different proportions of methane doping were investigated. The influence of methane doping on soot formation of ethylene/hydrogen (30% hydrogen) laminar diffusion flame was studied. Results show that the order of soot in the range of flame height less than 4 cm was significantly reduced when the methane mixing ratio was 3% and 7% respectively, indicating that there is an obvious synergistic effect in this region; when the methane doping ratio increased by more than 10%, the synergistic effect disappeared and the order degree of soot increased. The influence of methane on the composition of soot functional groups was obvious. After being mixed with methane, the relative content of aliphatic functional groups increased overall. With the gradual increase of the doping ratio of methane, the relative content of CH₂ reached the peak value. When the proportion of methane continued to increase, the relative content of CH₂ decreased. The content of aromatic functional groups in soot decreased significantly with the increase of flame height. When mixed with 3% and 7% methane, the content of aromatic functional groups increased significantly at the flame height of 2 and 3 cm, respectively. When mixed with over 10% methane, the content of aromatic functional groups decreased, which showed that a small amount of methane doping provided a new way for CH₃ and C₃H₃ generation. While CH₃ and C₃H₃ increased, C₂H₄ and C₂H₂ decreased insignificantly, which promoted the formation of PAHs. Continuous increase of methane reduced the formation of C₂H₂ and the formation of PAHs accordingly; as the relative content of aromatic decreased, the formation of soot was reduced. This study reveals the interaction between methane and soot formation in ethylene / hydrogen laminar diffusion flame. There is a synergistic effect to promote soot growth at low a methane doping ratio, but it disappears at a high methane doping ratio.