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