Experimental investigation on dynamic characteristics of methane/air combustion in double‐layer pellets porous media.

The double‐layer porous media burner is considered as an effective way to realize stable lean‐burn. In order to quickly achieve a stable combustion state in a double‐layer porous media burner, this work investigated the dynamic characteristics of methane/air premixed combustion in a bench‐scale double‐layer porous media burnspanning from ignition to stable combustion and ultimately flameout. The experimental results indicate that regulating the equivalence ratio and the inlet velocity enables the establishment of a stable flame front and the φ = 0.75 and the Vin = 0.20 m/s are the appropriate start‐up conditions. The average propagation velocity of the combustion wave variation along the axial direction and ranged approximately from −0.022 to −0.078 mm/s. Moreover, the transition time to a stable combustion state is reduced by nearly 47.14% as the equivalence ratio increases from 0.60 to 0.70. During start‐up stage, there are significant fluctuations in CO and NOx concentrations, but both emissions remain low during steady combustion state, with the maximum concentrations of 37.5 and 40.2 mg/m3, respectively. Furthermore, the porous media combustion exhibits a pronounced re‐ignition capacity. At higher equivalence ratios, longer interruptions of premixed gas are allowed. [ABSTRACT FROM AUTHOR]