A heat-recirculating combustor with multiple injectors for thermophotovoltaic power conversion

A novel configuration of a heat-recirculating combustor with multiple injectors for 10-30 W power-generating thermophotovoltaic (TPV) systems is suggested. For the combustor as a heat source the combustion stability limits of premixed butane-air flames, the temperature distribution on the outer wall surface and the spectral emissive power density onto photovoltaic cells are measured to evaluate the combustion and radiation performance. Results show that the combustor can sustain stable burning and effective and uniform heat transfer for a wide operating range, due to the heat-recirculation using a cylindrical emitter with a quartz shield and a recuperator. Two distinct combustion stability limits, i.e., flashback and blowout limits, are observed, and a somewhat extended stable-burning regime is found for the combustor with a finned recuperator and closer injectors. The recuperator and injector geometry also affects the temperature distribution on the emitter wall surface. A silicon carbide (SiC) emitter shows higher spectral emissive power density than the stainless steel emitter, due to higher surface temperature and emissivity, and the emissive power density is further enhanced by applying the photonic crystal structure on the SiC emitter surface, due to the optical resonance effects. Thus, the present combustor configuration can be used in practical TPV power systems.