Kinetic enhancement of mesoscale combustion using a novel nested doll combustor

A novel, two-staged micro-scale combustor consisting of a sub-millimeter scale catalytic reactor and a meso-scale quartz main combustor is designed and analyzed. The performance of the micro-scale combustor is tested for both gaseous and liquid fuels, resulting in stable combustion for both cases. In the experiment, varying mixtures of 1-butene and air flow through a micro-scale catalytic tube to generate a radical source for the main combustor. The results show that this catalytic reaction can significantly extend the lean and rich flammability limits and sustain combustion at significantly lower flow rates. This presents clear evidence that radical addition plays an important role in flame stabilization in mesoscale combustion. Passing liquid ethanol in the outermost shell produces a much lower outside wall temperature, which implies heat recirculation within the burner. Analytical heat transfer calculations support this claim as well. A two-dimensional numerical simulation of methane-air flames with detailed chemistry is calculated in a simple geometry with and without radical addition to illustrate the benefit of the micro-tube. A three-dimensional numerical simulation with simple chemistry shows the improved mixing caused by the micro-tube. The results of this report indicate that a small amount of radical addition can significantly stabilize the flame, and that this design successfully integrates the efficiency-enhancing mechanisms of radical addition, heat recirculation, and augmented mixing.