Interactions between heat transfer, flow field and flame stabilization in a micro-combustor with a bluff body

Abstract

We recently developed a micro bluff body combustor. Both experimental and numerical investigations demonstrated that the bluff body can significantly extend the blow-off limit. In the present paper, the effect of solid materials (i.e., quartz, stainless steel, and SiC) on the blow-off limit of this micro-combustor was investigated numerically. The results show that the blow-off limit of the quartz combustor is the largest, while that of the SiC combustor is the smallest. The underlying mechanisms were analyzed in terms of the interactions between the flow field, heat transfer processes and flame stabilization. It is demonstrated that when the thermal conductivity is small (i.e., quartz), less heat is conducted to the upstream walls, the fresh mixture is not sufficiently preheated and the gaseous volume does not expanded so significantly. Therefore, the flame stretching effect is weaker than the other two cases and thus a larger blow-off limit is achieved. Moreover, for the stainless steel and SiC micro-combustors, a larger thermal emissivity (i.e., SiC) results in a bigger ‘total heat loss ratio’ and a smaller blow-off limit. In summary, a solid material with relatively low thermal conductivity and emissivity is beneficial to obtain a large blow-off limit for the micro bluff body combustor. The present study also demonstrates that both flow and heat transfer processes, as well as their interactions, play an important role in flame stabilization of the micro bluff body combustor.