An Experimental Investigation of a Mini-Scale Porous Mmedia Combustor for Hydrogen Combustion

This study discusses low thermal load and NO emissions in a mini-scale porous media combustor, as well as stable combustion were examined via quartz tube observation. The materials of porous media were OB-SiC, Al₂O₃ and ZrO₂, and three types of porous media arrangement were examined in this experiments. The results showed that stable combustion of hydrogen fuel was obtained under different equivalence ratios and thermal loads. The hydrogen conversion rate and NO concentration in the exhaust gas depended on the flame position and thermal loads. When surface combustion occurred, the hydrogen flame was located on the surface of downstream porous medium, and the reaction temperature and residence time were lower under a low equivalence ratio and thermal load, and the conversion rate of hydrogen and NO concentration were also lower. When interior combustion and a conical flame occurred, hydrogen flame was located on the interface of two porous media and a divergent section of the combustor. The reaction temperature and residence time were both higher with interior combustions than with surface combustion. With a higher equivalence ratio and thermal load, the conversion rate of hydrogen also rose due to the longer reaction time. High temperature conditions prompted the thermal mechanism of NO formation. The NO concentration of the exhaust gas was kept low due to the low temperature and residence time under lower thermal loads and equivalence ratios. In contrast, the NO concentration of the exhaust gas increased under a higher thermal load and equivalence ratio. Overall, the results show that stable combustion performance and low NO emissions can be achieved by using hydrogen fuel and a porous medium arrangement in a mini-scale combustor.