Reactive structures of hot diluted methane counter-flow diffusion flames have been characterized under air-fuel and oxy-fuel combustion condition, by using a standard OPPDIF code with a WSGGM model and a validated detail chemical mechanism. The result shows the gaseous radiation makes the peak temperature be lower and the distributions of temperature change greatly.
Characteristic of vanishing of pyrolytic region and increasing of thickness of heat release zones are investigated in detail. The reason for these is the overlap of zones for the positive heat release and the negative heat release. Meanwhile, the combustion regions are established based on Xf –Tf –ΔT sketch map. The results show that MILD combustion is easier to be achieved under oxy-fuel conditions but it is also easier to blown off.
Moreover, reaction pathways for feedback combustion and MILD combustion under both air- and oxy-fuel conditions are analyzed. The chemical reaction rate decreases one order of magnitude under MILD combustion. Also, the decreasing of the production of OH and H and the addition of CO2 makes the C1 branch the C2 branch changes greatly under both conditions for MILD combustion.