A dual-channel micro-combustor with isolated catalytic hydrogen combustion for efficient ammonia/hydrogen utilization

To overcome the storage and safety challenges associated with hydrogen, ammonia has emerged as a practical carbon-free fuel for power systems. However, its sluggish kinetics and low reactivity hinder stable and efficient combustion. Although catalytic hydrogen combustion can effectively promote gas-phase ammonia oxidation through thermal and chemical coupling, the accumulation of nitrogen-containing surface intermediates can inhibit catalytic activity on noble-metal surfaces, limiting the effectiveness of direct catalytic ammonia combustion. To circumvent this limitation without increasing geometric complexity, a novel dual-channel planar micro-combustor is proposed, in which a fuel-lean hydrogen/air mixture undergoes catalytic combustion in an adjacent upper channel, while a fuel-rich ammonia/hydrogen/air mixture flows through the center channel without contacting the catalyst. Numerical simulations using a validated coupled hetero-homogeneous kinetic model reveal that the heat and reactive radicals generated in the catalytic channels enhance and support gas-phase flame anchoring within the downstream blending zone, where the two streams merge. Parametric investigations covering side-channel equivalence ratios of 0.35–0.55, center-channel equivalence ratios up to 7.5, blending ratios of 0.1–0.5, and center-channel inlet velocities of 1.7–2.5 m/s demonstrate that the proposed combustor can reproduce the thermal performance of a pure-hydrogen baseline (outlet temperature of 1457 K). Under the best-performing investigated condition ( φ 1 = 0.5 , φ 2 = 3.1 , X = 0.3 ), both ammonia conversion and combustion efficiency exceed 95 %, while the total hydrogen mass flow rate is reduced by 34.6 %. These findings demonstrate an effective strategy for minimizing hydrogen dependence by exploiting hetero-homogeneous coupling while completely avoiding direct ammonia catalyst interaction.