Investigation of no emission characteristic of ammonia-hydrogen flame in a two-stage model combustor

Abstract

The laminar burning velocity and NO formation process of ammonia-hydrogen combustion within a two-stage combustion chamber were investigated numerically in the present study. A chemical reactor network method involving perfectly stirred reactor, plug flow reactor, and partially stirred reactor configurations with the 24-species Xiao mechanism was implemented to simulate the premixed ammonia-hydrogen-air combustion process. The effects of inlet temperature and pressure conditions on the laminar burning velocity were investigated. Results proved that elevated pressure condition decreased primary flame thickness leading to lower laminar burning velocity while inlet temperature increased flame temperature which in turn increased the laminar burning velocity. Investigation of the effect of humidification on the laminar burning velocity showed that humidification can counteract the effect of high inlet temperature. The NO emission studies indicated a twofold impact of pressure on NO formation processes: preventing NO formation in the primary combustion zone, and promoting thermal NO formation in the lean combustion zone. The minimum amounts of NO emission were obtained at total equivalence ratios of 0.4. Humidification prevented the NO formation in the lean combustion through the competitive effect of H2O on O, whilst temperature effect was comparatively small. Humidity and pressure were optimized in the two-stage configuration achieve both low emission and high efficiency.