High-resolution dynamic characteristics of thermal wave in porous media burners with low-concentration methane

Thermal flow reverse reactor can realize stable oxidation and heat release of low-concentration coal mine methane, while the dynamic characteristics of thermal wave warrant further investigation. In this work, the temperature field of porous media with a high spatio-temporal resolution was obtained in an optically accessible burner using a short-wave infrared camera (SWIR). The effects of operating conditions and structural parameters on the thermal waves were investigated experimentally. The results indicate that SWIR thermometry is more accurate than long-wave infrared thermometry (LWIR) and thermocouples in measuring the temperature of thermal wave. The ability of porous media to broaden the flammability limit is better at pore diameter Dp = 2.3 mm than that at Dp = 1.7 mm and Dp = 3.4 mm. The large flow velocity enhances the stability of the thermal wave and increases the speed of the thermal wave. The average temperature and maximum temperature of thermal wave are positively related to the equivalence ratio, with the maximum temperature rising from 889 °C to 925 °C when the equivalent ratio increases from 0.40 to 0.6. The acquisition of the comprehensive characteristics of thermal wave can help to improve the combustion stability of low-concentration methane and further extend the lean flammability limit.