Ignition and extinction of surface and homogeneous oxidation of NH₃ and CH₄

Abstract

Abstract Ignition, extinction and autothermal behavior of surface and homogeneous oxidation reactions of CH 4 , NH 3 , and mixed NH 3 /CH 4 fuel systems in air over resistively heated Pt foils was studied in an atmospheric pressure flow reactor. Also examined were the effects of varying fuel concentration on the ignition, extinction, and autothermal surface temperatures. Heterogeneous ignition occurred at ∼200°C for NH 3 and at ∼600°C for CH 4 . The mixed fuel systems exhibited two surface ignitions (∼200°C and ∼600°C), implying a sequential ignition of the two fuels. The effects of removing one of the fuels during autothermal operation gave results consistent with this hypothesis. In homogeneous ignition, two types of flames were observed: a boundary layer flame associated with NH 3 systems and an independent flame observed in all systems. Homogeneous ignition of the two fuels and the mixtures occurred at surface temperatures ranging from 1,100°C to 1,600°C and appeared to be dominated by CH 4 in the mixed systems. A generic behavior is proposed for homogenous‐heterogeneous combustion of single and mixed fuels.