Sustainable Dual‐Fuel Combustion of NH 3 /CH 4 : Role of Equivalence Ratio Pairing in Flame Dynamics and Emissions

Ammonia (NH 3 )/methane (CH 4 ) dual‐flame combustion offers a promising strategy to enhance NH 3 utilization while mitigating NO x emissions. However, the effects of individual flame equivalence ratios on flame behavior and pollutant formation remain inadequately understood, particularly under stoichiometric and rich CH 4 conditions. This study investigates the effects of independently controlled CH 4 and NH 3 equivalence ratios ( and , respectively) on flame dynamics and emissions in a dual‐flame system. Experiments were conducted using a triple‐slot burner, with a central premixed NH 3 /air jet and two inclined CH 4 /air side jets, forming a stable, quasi‐two‐dimensional flame. Direct flame imaging reveals that CH 4 enrichment accelerates NH 3 reactivity, shortens flame height, and lowers the threshold for tip‐opening transition. Particle image velocimetry (PIV) measurements confirm the presence of a backflow region near the exit of the central nozzle that facilitates NH 3 flame attachment. However, its confined spatial extent suggests it is unlikely to be the dominant factor driving the enhanced NH 3 reactivity observed under higher . Chemiluminescence imaging (NH 2 ∗ , CH ∗ ) suggests a significant role of radical diffusion and CH 4 transport in modifying the local equivalence ratio and fuel composition within the NH 3 reaction region, thereby playing a central role in stabilizing the NH 3 flame. Emission analysis shows that increasing reduces NO and CO emissions under lean conditions, though excessive enrichment can promote NO via fuel‐NO pathways. CO–CO 2 trends further suggest carbon‐nitrogen coupling via HCN formation. These findings highlight the critical role of equivalence ratio pairing in governing flame structure and emissions, offering insights for low‐emission NH 3 ‐based combustion design.