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

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