The Influence of CO<sub>2</sub> Physical Effects on the Combustion Characteristics of Methane Diffusion Flames

本文以天然气的烟气再循环技术为研究背景，主要研究CO2气体的加入对CH4/空气同轴射流层流扩散燃烧火焰影响。采用数值模拟方法，对CO2气体的物理特性对火焰温度，CH4反应速率峰值和火焰尺寸的影响分别进行分析，为深入研究CH4火焰燃烧特性提供基础模拟理论的分析依据。研究结果显示，当空气中的部分N2被CO2代替后，火焰的燃烧温度会随着当量比的增加而降低，随着CO2体积分数的增加而降低，并且无论是在贫燃料燃烧还是在富燃料燃烧，这种变化趋势保持一致。而CO2的加入因其自身的高比重使得CO2进入燃烧室后具有较大的分子动量，更有利于燃料与氧化剂混合发生反应，因此使得CH4/空气反应速率的峰值升高，但并没有提高CH4的燃烧效率。火焰尺寸不因CO2的加入而发生变化，但随着当量比的增加而减小。This study investigates the influence of CO₂ addition on CH₄/air coaxial jet laminar diffusion flames within the context of flue gas recirculation (FGR) technology for natural gas combustion. Numerical simulations were conducted to analyze the effects of CO₂ physical properties on flame temperature, peak CH₄ reaction rate, and flame dimensions, providing foundational theoretical insights for further research on CH₄ flame combustion characteristics. Results indicate that substituting N₂ in air with CO₂ leads to a reduction in flame temperature, which decreases with both increasing equivalence ratio and CO₂ volume fraction. This trend remains consistent under both fuel-lean and fuel-rich combustion conditions. The introduction of CO₂ enhances the peak CH₄ reaction rate due to its higher molecular momentum, which promotes fuel-oxidizer mixing. However, no significant improvement in CH₄ combustion efficiency is observed. Flame dimensions remain unaffected by CO₂ addition but decrease with increasing equivalence ratio.