Large eddy simulation on flame topologies and the blow-off characteristics of ammonia/air flame in a model gas turbine combustor

Abstract

Ammonia (NH3) is recently identified as one of the suitable energy carriers in hydrogen energy system. However, regarding NH3 as a fuel is still facing several challenges which limit the direct use on modern combustion systems. The main challenge is the difficulty to stabilize NH3/air flames. To reveal and analyze the stabilization mechanism and the characteristics during blow-off processes in a swirl combustor, large eddy simulation with thickened flame model was performed to resolve the three dimensional swirl NH3/air flame. The CH4/air flame was also performed for comparison. The reacting flow fields and the flame structures were measured by PIV and OH-PLIF technique respectively. For NH3/air flame, flame fronts are burning to the higher equivalence ratio region, which leads to a larger trend of extinguishing. The curvature distribution at flame root is mainly dependent on the flame characteristics. Downstream the flows, the curvature distribution is mainly influenced by the flow field characteristics. Though the value of wall heat loss of NH3/air flame is less than that of CH4/air flame, the heat loss still shows greater influence on NH3/air flame stabilization when considering the lower heat release rate of NH3/air flame. The blow-off of CH4/air flame is mainly caused by the decreasing HRR and heat loss, while for NH3/air flame, it is a combined effect of the excessive stretch, the reduction of HRR as well as the greater heat loss effect.