Assessment of the impact of using Ammonia-Hydrogen fuel blend in a diffusion combustor: A numerical approach

The objective of this study is to investigate the effect of using an Ammonia-Hydrogen fuel blend in a diffusion furnace (Harwell furnace) with varying swirl numbers through numerical simulations. The commercial CFD software Ansys Fluent 2023 R1 was employed, utilizing the Okafor mechanism and the Eddy Dissipation Model (EDM) for species transport. Radiation heat flux and turbulent flow characteristics were modeled using the Discrete Ordinates (DO) method and the standard k-ϵ model. The study examined volumetric ratios of Ammonia-Hydrogen ranging from 0% to 100% and swirl numbers from 0 to 1. Key findings demonstrate that increasing the hydrogen content in the blend elevates peak flame temperatures, while higher ammonia concentrations result in broader, cooler flames due to the slower combustion kinetics of ammonia. Swirl numbers significantly influence flame stability and temperature distribution, with higher swirl numbers (S.N ≥ 0.6) promoting better mixing, uniform temperature profiles, and reduced pollutant emissions, particularly N_2 O and NO_2. The optimal operating conditions were identified as a swirl number of 0.6 with an Ammonia-Hydrogen blend ratio of 30–50%, achieving a balance between high combustion efficiency and low emissions. These results demonstrate the potential of Ammonia-Hydrogen blends in diffusion combustors for cleaner energy applications.