对丙烷/空气在内径2 mm的圆管内的预混燃烧进行了实验研究,借助于高速数码摄像机发现了分裂火焰现象,其中一个为向上游传播的较亮的常规火焰,另一个为向下游传播的较暗的微弱火焰。这些火焰先后熄灭,经过一段时间后又重复发生自着火、分裂、反向传播、灭火过程。这种现象在富燃、化学恰当比以及贫燃火焰中都有存在。一维非稳态计算表明化学反应速率的轴向分布曲线存在大小不同的两个峰值,它们分别对应实验观察到的两个不同亮度的火焰。其中,常规火焰是由于向上游较冷的壁面散热而熄灭,微弱火焰则是由于下游燃料耗尽而熄灭的。
Premixed combustion of propane/air mixture was experimentally and theoretically investigated in a heated micro tube of 2.0 mm inner diameter.Splitting flames were observed with an image-intensified high-speed digital video camera.After auto-ignition of the mixture,the reaction front splits into an ordinary flame and a weak flame.The former propagates upstream whereas the latter moves downstream and finally they both extinguish.After some delay,re-ignition of fuel-air mixture occurs and flame splitting process repeats.This phenomenon was identified in rich, stoichiometric and lean mixtures.It was reproduced by a thermo-diffusive model with global one-step chemistry.The computation results demonstrate that the ordinary flame is quenched by heat loss to the cold wall in the upstream region,while the weak flame is extinguished by consumption of fuel in the downstream region.
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