NUMERICAL ANALYIS OF AMMONIA/HYDROGEN FLAMES IN A SWIRL AND BLUFF-BODY STABILIZED BURNER

Abstract

Ammonia (NH3) is a possible and attractive substitute of hydrocarbon fuels in the path towards achieving clean energy goals. Key obstacles that require immediate attention are its relatively low reactivity and high NOx emissions. A proper investigation of both issues call for an in depth consideration of the near burner flow aerodynamics. CFD has played a significant role in suggesting innovative burner designs to overcome particular problems under circumstances of single and two-phase reacting flows. This study is part of a broader investigation dealing with the development of a novel combustor for ammonia firing. Reynolds Averaged Navier Stokes (RANS) analysis of a swirl and bluff-body stabilized burner firing various mixtures of NH3 and H2 was performed. The effect of the burner configuration and H2 content in the fuel mixture on the internal recirculation zone was examined. As the firing conditions imply non-diffusion flame, both premixed and partially premixed combustion modelling with various combustion models were used for the investigation. Three stoichiometric mixtures with pure ammonia, 25% H2 and 50% H2 blends were studied. In some cases, simulations suggested flash back into the 'fresh charge' tube preceding the chamber. While the flame for pure ammonia firing was longer, the introduction of hydrogen in the fuel mixture increased the reactivity, as typified by the higher temperature and product formation rate.