Effect of hetero-/homogenous combustion on energy conversion performances and flame stability of methane/air-fueled micro-combustors with heat-recirculating structure and platinum-coated.

• The impact of Pt catalyst and heat recirculation on combustion performance is evaluated. • The homogenous chemistry can be substantially extended in the presence of a catalyst. • Outer wall temperature and uniformity are enhanced with proposed strategies. • Radiation energy and efficiency exhibit a different trend with the inlet flow rate. In this work, the joint effect of applying Pt catalyst and heat-recirculating structure on the flame stability and thermal performance has been numerically investigated in methane-air-fueled micro-combustors by a detailed three-dimensional computational model. Numerical results indicate that such strategies contribute to improving outer wall temperature by 14.4% and extending the blowout limit by a factor of 0.6 compared to those in the straight non-catalytic combustor. Such enhancements are due to the intensified heat transfer, thus highlighting the contributions of heterogeneous combustion chemistry and heat-recirculating effect. Homogeneous chemistry in the presence of a Pt catalyst is shown to be self-sustained over wide-ranging conditions. Meanwhile, the effectiveness of heat recirculation structure on combustion performance is more significant as compared to that of the catalytic combustion effect, as evidenced by a 4% and 17.6% improvement in the wall mean temperature and blowout limit respectively. Further analysis of the heat recirculation catalytic combustors is conducted to obtain the optimal geometry. There exists a critical flow rate corresponding to the maximum outer wall temperature and radiation energy. In general, this work demonstrates the viability of applying a Pt catalyst and heat-recirculating structure to extend the flame stability limit and energy conversion performance in micro-power systems. [ABSTRACT FROM AUTHOR]