Turbulent burning velocity of ammonia/oxygen/nitrogen premixed flame in O₂-enriched air condition

Ammonia is a promising hydrogen-energy carrier as well as a carbon-free fuel. However, turbulent burning behavior of ammonia flame had yet to be sufficiently studied. In this work, laminar and turbulent burning velocities of ammonia/oxygen/nitrogen flames were investigated under the condition of oxygen enrichment. The turbulent burning velocity of ammonia/oxygen/nitrogen mixtures was found to increase with increasing turbulence intensity. The ratio of the turbulent burning velocity to stretched laminar burning velocity, U_tr/U_N, increased with the turbulence Karlovitz number. However, because of the diffusional–thermal instability effect, given the same turbulent Karlovitz numbers, U_tr/U_N in ammonia-lean cases is larger than in ammonia-rich cases. These findings indicate that consideration of the effects of diffusional–thermal instability and of the turbulence is important for the prediction of turbulent flame propagation velocity in ammonia combustion fields.