Effect of Coal Spontaneous Combustion Gases on the Laminar Burning Velocity of the CH4/Air Premixed Flame

In order to investigate the effect of coal spontaneous combustion (CSC) gases such as CO, C₂H₄, C₂H₆, C₃H₈, C₂H₂, and H₂ on the laminar burning velocity (LBV) of the CH₄/air premixed flame, a constant volume chamber and a high-speed camera were used to measure the LBV of a 90% (in vol) CH₄ and 10% CSC gas mixed fuel at an initial temperature of 300 K and over a wide equivalence ratio range from 0.7 to 1.3. Results show that the addition of all the CSC gases increases the LBV of CH₄. Among all CSC gases, the CH₄/C₂H₂ mixed fuel has the highest LBV, and the CH₄/CO mixed fuel has the lowest LBV. With the addition of three typical stages of CSC gases, the LBV of CH₄ was significantly enhanced. Based on the reaction path, mole fraction, and rate of production analysis, it is found that the addition of CSC gases in Stage 2 can increase the concentration of C₂H₅ and the consumption rate in the CH₃–C₂H₆–C₂H₅ path, which is different from Stages 1 and 3. In addition, all the concentrations of H, O, and OH free radicals increase with the addition of three typical stages of CSC gases.