Combustion characteristics of nonpremixed ammonia-hydrogen/air coaxial flames in a model combustor

초록

Based on the idea of ammonia (NH3) thermal cracking, NH3-hydrogen (H2) blends are emerging as a representative carbon-free fuel. To build a comprehensive database for the industrial use of the blends, this study investigates the combustion characteristics of nonpremixed NH3-H2/air coaxial flames in a model combustor across various conditions of H2 mole fraction in fuel (xh,f), fuel velocity (uf) and injection fuel-equivalence ratio (ϕ). Flame length reaches its maximum values near the stoichiometric condition. As xh,f and uf increase, heat flux increases, showing the higher radiative intensity of H2O compared with the NH2 α bands downstream. Also, flame wrinkling is intensified with increasing uf. In the nonpremixed flames, not only strain-induced but fuel-lean extinction is observed with local extinction occurring at flame base. Unlike in premixed flames, nitrogen oxides (NOx) emissions consistently increase with decreasing ϕ and xh,f due to the predominance of fuel NOx. Unburned NH3 emissions increase with increasing ϕ and decreasing xh,f. © 2025 Elsevier Ltd

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