CH4/NH3 Flame Structure and Extinction Limit under Flame–Flame Interactions

Ammonia is considered to play an important role in replacing traditional fossil fuels in future energy systems. In the experimental study, CH4/NH3 flame was lit by applying a double-nozzle burner to gain insight into the structure, and the laminar diffusion flame structure, CH*/OH* intensity maximum, and flame size were analyzed by an ICCD camera. In addition, the extinction limit (lower limit) of the CH4/NH3 flame under different conditions was also studied. The results showed that with the increase of burner pitch, the two diffusion flames showed four states of merged flames, merging flames, inclining separated flames, and independent flames in turn. In the process of flame separation, the continuous pitch between merging flames was short. At this point, higher syngas flow could help increase the continuous pitch to keep merging form. The paper investigated the flame structure and found that the flame size would decrease when the NH3 content in the fuel was high. The flame stability also decreased with an increase of the NH3 content in the fuel. These findings provided experimental proof and a theoretical basis for future studies on the stability of CH4/NH3 co-firing.