Thermal and chemical analysis on the hetero-/homogeneous combustion characteristics of H2/Air mixture in a micro channel with catalyst segmentation

•Hetero-/homogeneous combustion characteristics are observed in a micro reactor.•Gaseous flame is against the heterogeneous reaction in the micro catalytic channel.•Heat feedback from homogeneous reaction on catalyst promotes heterogeneous reaction rate.•Released heat from heterogeneous reaction improves the homogeneous reaction rate.•The effects of catalytic surface are more pronounced for micro combustion schemes. The heterogeneous-homogeneous combustion characteristics of premixed H2/Air mixture in a micro combustor with 2 mm platinum (Pt) catalyst segmentation are investigated by numerical simulation. The detailed chemical reaction mechanisms of gas-phase reaction and surface reaction of H2 are employed in a 2D CFD model by the verification. The characteristics in the catalytic combustor, such as temperature distribution, species concentration, kinetics reaction rate and heat transfer, are examined by varying inlet flow velocities. There is an interesting fact that an obvious demarcation line splits the channel into two regions at high velocities, which are dominated by heterogeneous reaction (Htr) and homogeneous reaction (Hr). In addition, there is a coupling heterogeneous-homogeneous reaction (HHr) in the 2 mm downstream of the catalytic region. These should be thoroughly deliberated using thermal and chemical analyses to determine that the gaseous flame is against the Htr in the catalytic combustor. The results can be shown that the heat flux into the upstream catalytic wall is primarily due to exothermicity induced by Htr. A low amount of heat feedback via the solid wall to inlet wall which is released by Hr. The heat fluxes from the gas–solid interface preheat the fresh gaseous mixture in the channel, thereby promoting the occurrence of Hr, increasing the heat release rate and kinetic reaction rate of Hr. Moreover, heat feedback from the heat release of Hr through the solid wall increases the reaction rates of Htr. The hydrogen conversion rate is improved by the effect of Htr in the catalytic combustor. In summary, the effect of introducing catalytic surface to induce the Htr could be well suitable for micro combustion schemes.