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This study compares the lean extinction behaviors of CH4 and a 16% cracked ammonia surrogate (CR16) in counterflow premixed flames, using experimental and OPPDIF simulations with GRI-Mech 3.0 and UCSD mechanisms. CR16 demonstrated superior extinction strain rates and resilience to strain-induced blow-out compared to CH4 under lean conditions, attributed to its longer flame time and sustained H2 consumption via nitrogen-related pathways near extinction. These findings elucidate the chemical mechanisms behind the enhanced extinction resistance of low-cracking-ratio ammonia fuels.
Cracked ammonia fuels exhibit significantly higher resilience to flame extinction under lean conditions than methane, driven by unique hydrogen and nitrogen chemistry sustaining combustion near blow-out.
In this study, the lean extinction behaviors of CH4 and a 16% cracked ammonia surrogate fuel, CR16, in counterflow premixed flames were compared. Experiments were conducted along with one-dimensional simulations using OPPDIF; the GRI-Mech 3.0 and UCSD mechanisms were applied to CH4 and CR16, respectively. CR16 exhibited higher extinction strain rates and resilience to strain-induced blow-out (RSIB) than those of CH4 under lean conditions. At Phi = 0.66, although both flames had the same extinction strain rate, CR16 showed a higher RSIB because of its longer flame time. Near its extinction, CR16 sustained H2 consumption, radical reactions, and heat release through the interflame region toward the stagnation plane. Hydrogen oxidation coupled with nitrogen-related pathways, including NH2 + NO and HNO reactions, supported this behavior. These results clarify the chemical basis for the superior extinction resistance of economically favorable low-cracking-ratio ammonia fuel.