Experimental and numerical studies of mixing and flame stability in a micro-cyclone combustor

A 30-W-class micro-cyclone combustor was developed as a heat source for a 1-W thermoelectric power generator (TPG). Methane gas was used as a fuel instead of liquefied fuel in this feasibility study for convenience. The combustion stability of the combustor was measured, and the flame shapes were visualized experimentally. Numerical simulations were performed to examine the details of the flame structure and flame stabilization mechanism inside the micro-cyclone combustor. The micro-cyclone combustor burned the supplied fuel stably inside the combustion chamber in the range where the combustor generated 30 W of heat energy. The mixing and flow characteristics of non-reacting and reacting flows in the combustor were examined using the simulation results. The mixing of the fuel with air in a non-reacting flow field was enhanced by increasing the equivalence ratio for a fixed fuel flow rate. For non-reacting flow, a recirculation region and a small negative axial velocity region near the injection ports were formed. The recirculation region became wider with decreasing equivalence ratios. For reacting flows, however, the recirculation region disappeared and the only small negative axial velocity region was formed near the fuel injection ports. The flame was stabilized inside the combustor because the flame base was anchored near the negative axial velocity region near the fuel injection ports.