Executive Summary : | Ammonia (NH₃) is a promising candidate for carbon-free fuels to reduce greenhouse gas emissions. However, it has low burning velocity, narrow flammability limits, and produces fuel-NOx in the exhaust. Enriching ammonia with hydrogen can enhance its combustion characteristics, but partial cracking or thermal decomposition of a fraction of NH₃ is advocated. A blend of NH₃/H₂/N₂ with H₂-N₂ in a 3:1 volume fraction is said to mimic partially cracked ammonia. This study aims to test different NH₃/H₂/N₂ blends with different NH₃ fuel fractions in a non-premixed swirl stabilized combustor at different swirl numbers. Flame stability limits and stable operating conditions will be tested for different blends, covering a wide range of blends. Critical NOx measurements will be made at all tested conditions to determine stable flame conditions producing minimum emissions. Recent studies have shown that NH₃/H₂/N₂ can burn lean with minimal emissions in the lean regime, which is desirable in non-premixed combustion systems. To predict blowout precursor events near the lean blowout limit, transient acoustic pressure inside the combustor and dynamic heat release rate from the overall flame in the form of OH* chemiluminescence signals will be analyzed. |