LES/TFM of turbulent ammonia premixed flames in a swirl-stabilized combustor

Ammonia is a high energy density hydrogen carrier that can be produced using renewable energy and used in hard-to-decarbonize applications. However, its combustion poses many challenges including low burning velocity, narrow flammability limits, low extinction strains, and higher NOₓ, N₂O emissions and NH₃ slip. Large Eddy Simulation (LES), well-suited for practical turbulent reacting flows, can be a powerful tool for the design of clean and stable ammonia combustion systems. To capture burning enhancement and related emissions, hydrocarbon-based turbulent combustion models must be adapted to the unique combustion characteristics of ammonia. This presentation discusses results of LES performed using a dynamic artificially thickened flame model (TFM) in a premixed combustion tunnel using swirl and sudden expansion to stabilize the flame, focusing on predicting the multiple recirculation zones and vortex breakdown bubble of the underlying flow, and the corresponding flame configurations at different equivalence ratios. A modified TFM formulation compatible with ammonia characteristics is coupled with a reduced chemical kinetic mechanism chosen for accuracy in predicting the flame and emissions. We show sensitivity of key physical flow/flame features to the TFM formulation, comparing the results to laboratory-scale measurements. Results emphasize the role of flow-chemistry interactions and offer a predictive framework for optimizing combustor design and emissions control strategies.