Comparative analysis of combustion and emissions performance of partially cracked ammonia (H2/N2/NH3) and NH3/H2 flames in a model gas turbine combustor

The present numerical study investigates the combustion and emission characteristics of partially cracked ammonia flames in a model gas turbine combustor under premixed swirl conditions. Higher NH3 cracking ratio leads to increased NO emissions and intensified combustion owing to higher H2 content, resulting in enhanced heat release with reduced flame length. Compared with 40% NH3/60% H2 flame , the cracked NH3 flame with a 60% cracking ratio achieved a reduction in NO emissions by approximately 25%, implying the advantage of lower NOx emissions. Detailed chemical reactor network analysis identifies the dominant NO formation pathway for cracked NH3 flame as HNO + OH ↔ NO + H2O at fuel-lean condition, while the principal NO consumption reaction across all conditions is NH + NO ↔ N2O + H. The reaction NH2 + O ↔ HNO + H plays a key role in NO formation under lean conditions for cracked NH3 flames, whereas for NH3/H2 flames, the NH + OH ↔ HNO + H becomes the dominant reaction driving NO production. Ammonia cracking plays a crucial role in enhancing the combustion kinetics of NH3 by generating reactive hydrogen species, thereby improving flame stability and combustion efficiency in gas turbine applications.