Abstract: Numerical study on premixed methane/ethylene/air flames with various ethylene fractions and equivalence ratios was conducted at room temperature and atmospheric pressure. The effects of ethylene addition on laminar burning velocity, flame structure and flame stability in lean condition were investigated. The results show that the laminar burning velocity is increased with the increase of ethylene fraction, especially at a large equivalence ratio. More ethylene addition gives rise to the increase of H, O and OH concentrations in the flame, which contributes to the enhancement of combustion, and a linear correlation exists between the laminar burning velocity and the maximum H+OH concentration in the reaction zone. With the increase of ethylene fraction, the adiabatic flame temperature is increased, while the inner layer temperature, the critical temperature at and above which reactions take place, is decreased, significantly promoting chemical reactions. Markstein length and Markstein number, representative of the flame stability, increase as more ethylene is added, indicating the tendency of flame stability to improve with the increase of ethylene fraction.

Key words: laminar burning velocity, flame stability, methane, ethylene

摘要： 在室温和大气压条件下，通过对不同当量比和不同乙烯含量的甲烷/乙烯/空气预混火焰进行数值模拟，研究了贫燃时乙烯添加对层流燃烧速度、火焰结构及火焰稳定性的影响。结果表明，层流燃烧速度随乙烯含量的增加而增大，在当量比较大时尤为明显；乙烯添加导致火焰中H、O和OH自由基浓度增大，从而促进燃烧，得到了反应区内层流燃烧速度与最高H+OH浓度的线性关系；随着乙烯含量的增加，绝热火焰温度升高，而反应发生的临界温度降低，有利于化学反应的进行；Markstein长度和Markstein数随乙烯添加而增大，表明火焰稳定性增强。

关键词: 层流燃烧速度, 火焰稳定性, 甲烷, 乙烯