Numerical comparison study of methane catalytic combustion characteristic between newly proposed opposed counter-flow micro-combustor and the conventional ones

Nowadays, combustion instability and low combustion efficiency are still two vital obstructions against the developments of microscale combustors. To handle and ease these two problems, a novel opposed counter-flow micro-combustor(C) with special multi-step separated baffles is proposed and compared with other two conventional micro-combustors (planar micro-combustor (A) and heat recirculation micro-combustor (B)). The catalytic combustion characteristics of CH4/air in three micro-combustors are numerically investigated using CFD software. Results show that with multi-step separated baffles, micro combustor C shows superiority in improving combustion efficiency at high inlet velocity and extending the inlet velocity limits for stable combustion with lower flow velocity distributions and enhanced heat recirculation. At the inlet velocity of 1.1 m/s, the combustion efficiency and blow-off limit of the opposed counter-flow micro-combustor increase by 18.34% and 165% compared with the planar micro-combustor, respectively. A significant supplement of CH4 is discovered in combustor C from the gaps between the separated baffles and this is also a key point resulting in the high combustion efficiency of micro combustor C. Besides, the new combustor also performs better in thermal cycling than normal heat recirculation micro-combustor with the preheat temperature deviation reaching 243 K at 1.1 m/s. (C) 2018 Elsevier Ltd. All rights reserved.