Explosion pressure and flame characteristics of CO/CH4/air mixtures at elevated initial temperatures

Abstract To investigate the effect of initial temperature on the explosion pressure and flame characteristics of CO/CH4/air mixtures, the explosion evolution and flame development were studied using a 20 L spherical tank and high-speed camera with variable CH4 concentrations (7 vol%, 9.5 vol%, and 11 vol%) and variable CO concentrations (0–2 vol%) under variable initial temperatures (25–100 °C). Temperature sensitivity analysis, key free radical evolution, and the reaction path for CO/CH4/air mixture explosion were investigated using the detailed mechanism of GRI-mech 3.0. The results indicated that (dP/dt)max, vmax, ignition delay time, and the explosion risk for the CO/CH4/air mixture increased when the initial temperature increased. For all CO/CH4/air mixtures, the top 5 intermediate reactions in terms of temperature sensitivity were fixed, following the order of #38 H + O 2 ⇌ O + OH , #53 H + C H 4 ⇌ C H 3 + H 2 , #155 C H 3 + O 2 ⇌ O + C H 3 O , #156 C H 3 + O 2 ⇌ OH + C H 2 O , and #158 2C H 3 + M ⇌ C 2 H 6 + M . A mixture with a higher CO content at a suitable range was more sensitive to temperature changes. After the addition of CO, most of the added CO undergoes an oxidation reaction, while a small amount of CO competes with the oxidation of CH4. The CO oxidation reaction, #99 OH + CO ⇌ H + C O 2 , was several times faster than that of the other branching reactions, but it occurred later. The maximum rate of production for CO generation was not affected by the addition of CO, while the maximum rate of production for CO consumption increased linearly with CO addition.