Effects of ammonia addition on combustion characteristics in partially-premixed swirling ammonia/methane/air flame

Abstract

Ammonia combustion has received intense research interest recently for its potential to reduce CO2 emission. This study aims to investigate the turbulent combustion characteristics in a bluff-body burner for CH4/NH3 mixtures with different ammonia blending ratios (15%, 30%, and 45% by mole fraction) through large eddy simulation and experiments. The simulations are conducted using openFOAM with a low Mach number solver and the partially stirred reactor combustion model with a detailed reaction mechanism. The flow field of one typical case is measured using the particle image velocimetry technique to verify the accuracy of the numerical results.The combustion characteristics are discussed. As the ammonia blending ratio increases, the flame height shortens, the flame color gradually changes from blue to orange, and the intermittent local quenching zone moves upstream, indicating that the combustion is becoming unstable. Meanwhile, the flow fields exhibit similar characteristics though the ammonia concentration varies greatly. The CO and NO emissions are also discussed. The CO emission decreases and the NO emission increases as the ammonia blending ratio increases