A Numerical Study Of Mesoscale Swiss-roll Combustors With A Bluff-body

Hydrocarbon fuels can contain more energy per unit mass than the best lithium-ion batteries in the world and be quickly charged, therefore combustion-based micropower systems has advantage over batteries for the application of MEMS. However because of bigger heat loss ratio, the fist problem faced by micro combustion is the stabilization of flame. The Swiss-roll combustor can obviously extend the lean flammability limit because of its preheating effect of the incoming gas, but it can't stabilize the flame at the center, which limit its flammable velocity range. Adding a bluff body within a micro-channel can significantly extend the blow off limits(the biggest flammable velocity). Therefore a mesoscale Swiss-roll combustor with a bluff-body was proposed in the present paper, which can fully utilize the anchoring mechanism of a bluff body and the heat recirculation of Swiss-roll configuration. It can both extend the blow off limits and the lean flammability limits. Through changing the size of bluff body and the thermal physical properties of solid materials, this paper mainly studies the effect of the complicated interaction of heat transfer?flow and chemical reaction on the flame stability.First, the effect of preheat temperature on the combustion of hydrogen and air in a micro straight tube is numerically investigated. The results show that the flame stability can be significantly strengthened by increasing the preheat temperature, which verifies inner mechanism of the excess enthalpy in the Swiss-roll combustor.Then the effect of bluff body and its size on the flame blow-off limit in the mesoscale Swiss-Roll combustors was numerically studied using a detailed chemical reaction mechanism. The results show that the formation of recirculation zone behind the bluff-body can obviously extend the blow-off limits, which fully prove the flame stabilization effect of bluff body. In addition, the influence of a bigger bluff body on the blow off limit is more significant than the smaller one.The effect of the thermal conductivity of solid wall and three different solid materials(quartz, stainless steel(SS), and SiC) on blow-off limit of a lean CH4/air mixture was numerically investigated. The results show that a smaller thermal conductivity leads to a wider flammable range. Besides that, the blow-off limit of the SS combustor is the biggest,followed by quartz combustor and SiC combustor, which is mainly because that the flame blow-off limit the mesoscale Swiss-Roll combustor with a bluff-body is mainly determined by the complicated interplay between heat loss effect, heat recirculation effect and the recirculation zone behind the bluff body.