Investigation of a Fuel-Flexible Diffusion Swirl Burner Fired with NH3 and Natural Gas Mixtures

The current investigation aims to develop a validated numerical model of a confined, swirl-stabilized diffusion flame. This model will assist in designing and optimizing novel combustion chambers while reducing computational costs. To achieve this objective, experimental and numerical studies were conducted on NH3/natural gas combustion using a laboratory-scale burner capable of operating under fuel-flexible conditions. The burner fired 5 kW flames of blended ammonia with natural gas in concentrations up to 100% NH3. The burner’s performance for relevant industrial applications was assessed through measurements of axial temperature profiles, exhaust temperature, and gas emissions. Numerical simulations were conducted by employing the commercial CFD software STAR-CCM+ 2020.2.1. Numerical simulations for steady-state were performed using a realizable k-ϵ turbulence model coupled with the EDC (eddy dissipation concept) for combustion. The investigation utilized a 3D periodic domain for the simulations and investigated mesh independence and the influence of the flame dynamics. The burner was able to operate with different fuel mixtures while maintaining stabilized flames under every condition. However, the appearance of increased ammonia slip was observed for 100% NH3 up to 1250 ppm (dry vol.). The present work demonstrates and assesses the readiness and potential of fuel-flexible burners as cost-effective and efficient transitional technologies for integrating ammonia and other sustainable fuels into combustion applications.