<br>CH4 层流扩散火焰的结构和高度的比较研究：燃料侧与空气侧稀释的影响,ACS Omega

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CH4 层流扩散火焰的结构和高度的比较研究：燃料侧与空气侧稀释的影响
ACS Omega ( IF 3.7 ) Pub Date : 2023-12-19 , DOI: 10.1021/acsomega.3c07406
Huanhuan Xu ₁ , Guangdong Zhou ₂ , Zilin Zhu ₂ , Zhiqiang Wang ₁

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引入稀释剂的策略是稀释燃烧中一个关键的实际问题。然而，目前还缺乏对燃料侧稀释与空气侧稀释的影响的全面了解。这项数值研究系统地研究了稀释策略对甲烷共流扩散火焰的影响，重点是火焰结构和火焰长度。将实际燃烧中常见的添加剂，特别是H ₂ O和CO ₂引入燃料或空气流中，稀释比( Z )范围为0到0.2，并对四种稀释策略的影响进行了量化和排名。使用经过充分验证的二维 (2D) 火焰代码进行详细模拟，以深入了解 OH 形成、火焰附着、燃烧器喷嘴温度和火焰高度。对传热、分子扩散和化学动力学进行了系统分析。结果表明，与燃料侧稀释相比，将稀释剂引入空气流对抑制 OH 形成具有更深远的影响。此外，空气侧稀释对火焰附着的影响可以忽略不计，而增加燃料侧的Z则显着抑制火焰附着，后者的行为归因于CH ₄向氧化剂侧的质量扩散减少。当火焰附着减弱时，会导致从火焰底座到燃烧器的热传递相应减少。因此，与空气侧稀释比相比，燃料侧稀释比的喷嘴温度的降低更为显着。同时，观察到燃料侧稀释的Z对火焰长度的影响比空气侧稀释的更深远，并且从理论上阐明了控制这两种不同稀释策略的基本机制。

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Comparative Study of the Structure and Height of CH4 Laminar Diffusion Flames: Effects of Fuel-Side versus Air-Side Dilution

The strategy for introducing diluents is a critical practical concern in diluted combustion; however, a comprehensive understanding of the effects of fuel-side dilution versus air-side dilution is currently lacking. This numerical investigation systematically studied the effects of dilution strategies on methane coflow diffusion flames, with a focus on the flame structure and flame length. Common additives in practical combustion, specifically H₂O and CO₂, were introduced to either the fuel or the air streams, with dilution ratios (Z) ranging from 0 to 0.2, and the impacts of four dilution strategies were quantified and ranked. Detailed simulations were conducted using a well-validated two-dimensional (2D) flame code to gain a deep understanding of OH formation, flame attachment, temperature of the burner nozzle, and flame height. Systematic analyses in terms of heat transfer, molecular diffusion, and chemical kinetics were conducted. Results demonstrate that introducing diluents into the air stream exerts a more profound influence on suppressing OH formation compared with fuel-side dilution. Moreover, air-side dilution has a negligible influence on flame attachment, while increasing Z on fuel side significantly inhibits flame attachment, and the latter behavior is attributed to the diminished mass diffusion of CH₄ toward the oxidizer side. As the flame attachment weakens, it causes a consequential reduction in heat transfer from the flame base to the burner. Accordingly, the nozzle temperature exhibits a more remarkable decrease with the fuel-side dilution ratio than with the air-side dilution ratio. Simultaneously, a more profound influence of Z on flame length was observed for fuel-side dilution than for air-side dilution, and the underlying mechanisms governing these two distinct dilution strategies were theoretically elucidated.

更新日期：2023-12-19

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