甲烷/空气混合物在微小型钝体燃烧器中的燃烧特性

为了实现在淬熄距离以下的稳定燃烧,试验设计了两种带钝体的回热型燃烧器,研究预混甲烷在高度小于淬熄距离的燃烧室中的燃烧特性。燃烧器的燃烧室高度为2 mm,长度为20 mm,进口处安装了边长为1mm的等边三角形钝体或相同尺寸的"V"形钝体,并在上下两侧设置了预热通道。利用Fluent6.3软件对甲烷/空气在这两个燃烧器的预混燃烧做了数值模拟,确定了浓度极限和速度极限,并对稳燃机理进行了分析。与三角形钝体燃烧器相比较,"V"形钝体燃烧器的稳燃范围更大。在所给出的稳定燃烧工况下两者的燃烧效率均在99%以上,甲烷/空气的混合气体能够完全燃烧。但当进气速度较小同时当量比较大时会发生回火现象。

Combustion characteristics of methane/air mixture in micro-scale combustors with different bluff-bodies

Two kinds of combustors with a height less than the quenching distance were designed and the combustion characteristics were studied for stable combustion.The gap distance of the combustion chamber is 2 mm,and the length is 20 mm.An equilateral triangular bluff-body with a side length 1.0 mm or a"V" bluff-body of the same size is fitted near the entrance of the combustion chamber.There are two preheating channels on the upper and lower sides of the combustion chamber.Numerical simulation on methane/air premixed combustion in these combustors was performed and both velocity limits and concentration limits of the systems were decided.Compared with the combustor with a triangle bluff-body,the stable combustion ranges of the combustor with a"V" bluff-body were enlarged.The combustion efficiencies all stayed above 99%.But when the inlet mixture velocity was too small and equivalence ratios were relatively high,flashback would happen.