Flame stabilization in a non-premixed ammonia-hydrogen-air micro-combustor with a 1 mm channel

Ammonia is increasingly being considered as a fuel for micro-combustors due to its economic viability, zero carbon emissions, and ease of transport. However, stabilizing ammonia flames in micro-combustors presents significant challenges, primarily due to substantial heat losses from the high surface-to-volume ratio, short residence times, and the low reactivity of ammonia. This study investigates a 1 kW non-premixed ammonia-hydrogen-air micro-combustor with a 1 mm channel, designed to stabilize flames with up to 38 % ammonia by volume and 83.9 % by mass in the ammonia-hydrogen fuel mixture. A two-dimensional computational model was developed using a reduced reaction mechanism. The numerical results were validated using data from the literature. Findings indicate that increasing ammonia mole fraction in the fuel mixture enhances energy output but lowers the blowout limit. Lean fuel analysis further revealed that combustion efficiency improves with lean mixtures, reaching a maximum of 99.9 % at a global equivalence ratio of 0.8. These results suggest that an ammonia-hydrogen mixture is a promising fuel for sustainable micro-combustion applications, offering a balanced approach that leverages the advantages of both fuels while mitigating their respective limitations. • 1 kW non-premixed 1 mm micro-combustor using ammonia–hydrogen fuel. • Stable flames with up to 38 % ammonia by volume (83.9 % by mass). • Higher ammonia increases energy output but lowers blowout limit. • Lean operation boosts efficiency to 99.9 % at global φ = 0.8