Experimental study and numerical analysis of the scaling effect on the flame stabilization of propane/air mixture in the micro-scale porous combustor

In order to investigate the effect of heat recirculation through the porous medium on the flame stabilization limits for different channel heights, micro-combustors with three different channel heights 3 mm, 2.5 mm and 2 mm are fabricated and tested. A three-dimensional numerical model is established to explain the inherent mechanisms for the experimental results. It is shown that the stable flame can be established inside the micro-scale porous combustor with the channel height 2 mm which is smaller than the quenching distance. The porous medium combustion limit remains nearly unchanged as the channel height decreases due to the enhanced heat recirculation through the porous medium and the solid wall. The extinction limit increases obviously with the decrease of channel height due to the excess heat loss. The simulation results show that the flame thickness becomes larger as the channel height decreases. With the decreasing channel height, the wall temperature increases due to the increase of inner-wall convection heat transfer coefficient. The thermal balance analysis shows that the decrease of channel height results in lower thermal efficiency. The 2 mm (ε = 4) height combustor is more suitable for the micro thermoelectric generator. Extra heat exchange channel is need to utilize the output energy sufficiently.