よどみ流中に形成されるEdge Flameの消炎特性と火炎構造(熱工学,内燃機関,動力など)
よどみ流中に形成されるEdge Flameの消炎特性と火炎構造(熱工学,内燃機関,動力など)
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停滞流中形成的边缘火焰的灭火性能和火焰结构（热工、内燃机、电力等）
DOI：
10.1299/kikaib.68.610
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
Masahiko Mizomoto
中科院分区：
文献类型：
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作者：
Hiroyuki Torikai;Akiko Matsuo;Toshihisa Ueda;Masahiko Mizomoto
利用自行研制的燃烧器，研究了甲烷-空气扩散火焰边缘火焰的喷吹特性与火焰结构的关系。该燃烧器可以在轴对称冲击射流的滞止区形成无预混火焰的边缘火焰，如孔洞。对边缘火焰的喷吹特性进行了测量，并对边缘火焰的结构、温度分布和火焰位置进行了测量，并利用激光层析技术对边缘火焰周围的热边界层进行了可视化。研究发现，滞流中所有的边缘火焰都存在一个临界滞流速度梯度，超过这个临界速度梯度，火焰将永远不会存在。代表边缘火焰区总反应速率的临界滞止速度梯度随着孔径的增大而减小。孔洞直径的增大导致了边缘火焰结构的变化，并增加了边缘火焰的两个热损失因子。其中一个热损失因素是边缘火焰与壁面的相互作用，这种相互作用是由于边缘火焰的位置降低而发生的。另一种是冷流穿透火焰中的小孔，这是由于小孔中边缘火焰的热边界层重叠范围减小所致。这些附加热损失发生在较低的滞止速度梯度处，并且随着小孔直径的增大对边缘火焰的影响更大。因此，随着孔直径的增加，边缘火焰区的总反应速率降低。当边缘火焰的火焰区在空间上作为氧化剂侧和燃料侧的分界线时，尽管在边缘火焰区反应区前方存在燃料和氧化剂的部分预混混合物，但边缘火焰在性质上与纯扩散火焰具有相同的熄灭效果。
The relation between blowoff characteristics of the edge flame in a methane-air diffusion flame and its flame structure has been investigated by using our original burner. The burner can form an edge flame without premixed flame, as a hole, in the stagnation region of an axisymmetric impinging jet. Varying the hole diameter, blowoff limits and maximum flame temperature were measured for an edge flame's blowoff character, and also, for an edge flame's structure, temperature profile and flame location were measured and a thermal boundary layer around the edge flame was visualized with laser tomographic technique. It is found that all the edge flames in the stagnation flow have a critical stagnation velocity gradient, beyond which the flame can never be existed. The critical stagnation velocity gradient that represents the overall reaction rate in the edge flame zone decreases as the hole diameter is increased. The increase in a hole diameter leads to change of the edge flame's structure and to addition of two heat loss factors to the edge flame. One heat loss factor is the edge flame-wall interaction, which occurs due to decrease in the edge flame's location. Another is penetration of cold flow into a hole in the flame, which occurs due to decrease in the overlapping range of thermal boundary layer of the edge flame in the hole. These additional heat losses occur at lower stagnation velocity gradient and have stronger influence on the edge flame as a hole diameter becomes larger. Consequently the overall reaction rate in the edge flame zone is reduced by the increase in a hole diameter. Finally it is clarified that the edge flame shows qualitatively same extinction as a pure diffusion flame, when the flame zone of the edge flame lies spatially as the boundary that divides between oxidizer side and fuel side in spite of existence of a partially premixture of fuel and oxidizer ahead of the reaction zone in the edge flame region.