Generalised correlations of blow-off and flame quenching for sub-sonic and choked jet flames
Generalised correlations of blow-off and flame quenching for sub-sonic and choked jet flames
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DOI：
10.1016/j.combustflame.2017.07.019
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发表时间：
2017-11
影响因子：
4.4
通讯作者：
A. Palacios;D. Bradley
中科院分区：
文献类型：
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作者：
A. Palacios;D. Bradley
由亚音速燃料射流火焰的数学模型和大量的实验数据所提出的无量纲组在用无量纲流数关联量纲火焰高度和火焰离地距离方面已经相当成功。这种方法被扩展到更严格的相关性，定义制度的火焰淬火，吹掉，并解除火焰。从这些不同的来源的实验数据进行了分析，这些制度的界限表示的临界最小喷管直径，以避免吹掉，规范化的层流火焰厚度的最大燃烧速度的混合物，和流量数。该制度从低雷诺数的皮下管层流延伸到高雷诺数的扼流，与超音速shocks.Data相关性很好，在亚音速范围内的碳氢化合物气体，在其中的临界管径，以避免吹出增加与流数。在扩展的阻塞流状态下，问题更为复杂，其中数据较少。超音速流和激波的这种状态是改进的燃料/空气混合和增强的反应性之一，达到临界管道直径在达到最大值之后减小的程度。数据在此制度，并确实在整个范围内的条件下，甲烷，丙烷和氢气射流火焰。氢气比碳氢化合物表现出更多的反应特性。在相关参数方面，而层流火焰厚度与非反应预热区的厚度有关，这样的区域很难用氢来定义，作为H原子上游扩散的结果，这方面进行了讨论。
Dimensionless groups suggested by the mathematical modelling of subsonic fuel jet flames, and extensive experimental data, have been reasonably successsful in correlating dimensionles flame heights and flame lift-off distances in terms of a dimensionless flow number. This approach is extended to the more exacting correlations that define regimes of flame quenching, blow-off, and lifted flames. Experimental data from these diverse sources are analysed, and the bounds of these regimes are expressed in terms of the critical minimum jet pipe diameter to avoid blow-off, normalised by the laminar flame thickness for the maximum burning velocity mixture, and the flow number. The regimes extend from low Reynolds number laminar flows in hypodermic tubes to high Reynolds number choked flows, with supersonic shocks.Data are well corrrelated in the subsonic regime for a range of hydrocarbon gases, in which critical pipe diameters for the avoidance of blow-off increase with flow number. Matters are more complex in the extended choked flow regime, in which there are less data. This regime of supersonic flow and shock waves is one of improved fuel/air mixing and enhanced reactivity, to such an extent that the critical pipe diameter, after reaching a maximum, decreases. Data are presented in this regime, and indeed over the full range of conditions, for methane, propane and hydrogen jet flames. Hydrogen exhibits more reactive characteristics than the hydrocarbons. In terms of the correlating parameters, whereas laminar flame thickness is related to that of the non-reacting preheat zone, such a zone is difficult to define with hydrogen, as a consequence of the upstream diffusion of H atoms, and this aspect is discusssed.