Combustion of hydrogen–air in catalytic micro-combustors made of different material

Abstract

Micro-combustors have low stability, thus catalyst is applied to improve it. In this experiment, the performances of catalytic micro-combustors made of different materials (quartz glass, alumina ceramic, copper) are compared. Asbestine threads are used as the catalyst supports of Pt, and installed in the combustors. According to the experimental results, the combustors have high stability, they keep working until the extreme equivalence ratio close to 0. The stability limits of homogeneous reaction in the quartz glass and alumina ceramic combustor range from 0.0907 to 8.69 and 0.158 to 7.31 on average, respectively. But the two combustors exhibit obvious hot spots, which are 1058 and 728 K at 0.2 L/min, respectively. Whereas the copper combustor has low and uniform temperature distribution on its surface. Moreover, the heat loss in the quartz glass combustor is 4.13 W higher than in the copper one at 0.2 L/min, which is opposite to the conventional situation that heat loss increases with the wall thermal conductivity. Computational fluid dynamic simulation reveals that the reaction modes inside the combustors differ. The higher wall thermal conductivity makes the heterogeneous reaction dominate, thus induces the temperature distribution and heat loss aforementioned.