Numerical Study on Hydrogen Heterogeneous Reaction Characteristic in a Micro Catalytic Combustor with Blunt Body

A numerical investigation has been conducted to explore the effect of an inserted blunt body on the heterogeneous reactions (HTR) characteristics in a micro-catalytic combustor operating with premixed hydrogen/air. The two-dimensional numerical model incorporates a comprehensive heterogeneous reaction mechanism of hydrogen employed by experimental verification. The influences of blockage ratio at various inlet velocities have been investigated to obtain optimized design parameters of the combustor. The findings of this research highlight analysis of the positive influence of an inserted blunt body within the combustor, including enhancement of chemical reaction rate and fuel conversion ratio. Numerical results showed that the gaseous mixture between the blunt body and catalytic surface noticed a considerable velocity increase, leading to a greater adsorption-desorption of bulk species on the catalytic surface. When the blockage ratio was less than or equal to 0.6, the average inner wall temperature and hydrogen conversion rate were positively affected by the increased blockage ratio. However, the effect becomes negative at higher blockage ratios (0.8). Moreover, through the analysis of various dimensionless numbers (, , ), it was found that the presence of a bluff body leads to a reduction in the channel cross-sectional area, an acceleration of fluid velocity near the bluff body, and an impact on the boundary layer near the gas-solid interface. This effect decreases the boundary layer thickness, enhancing the region's mass and heat transfer phenomena. Finally, the field synergy effects in a bluff body combustion chamber have been analyzed with different parameters. The study revealed that as the blockage ratio increases, the overall field synergy of the combustion chamber initially increases and then decreases. The findings of this study have important implications for the design of micro-scale combustors.