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.