Flame spread in an opposed turbulent flow
Flame spread in an opposed turbulent flow
复制标题
火焰在相反的湍流中传播
DOI：
10.1016/0010-2180(90)90068-3
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发表时间：
1990
影响因子：
4.4
通讯作者：
R. Cheng
中科院分区：
文献类型：
--
作者：
L. Zhou;A. Fernandez;R. Cheng
一项实验研究了在与火焰传播方向相反的气流中湍流对固体可燃物表面火焰传播的影响。改变流速及其湍流强度，观察它们对厚 PMMA 和薄滤纸片上火焰蔓延速率的影响。还观察到它们对火焰熄灭条件的影响。结果表明，对于厚 PMMA 片材，随着湍流强度的增加，铺展率先增加后减小。最大值的存在似乎是流动从层流过渡到湍流的结果，影响了从火焰到燃料的传热过程。通过干涉照片表明，扩散率随湍流强度的降低主要是由于火焰锋附近区域的对流冷却以及与火焰和表面辐射相关的其他不太重要的机制。对于薄纸，铺展率总是随着湍流的增加而降低。观察到的厚 PMMA 和薄纸结果之间的差异可能是由于它们在火焰前的传热机制不同。还发现，对于较高的湍流强度，火焰会在较低的流速下发生熄灭。这一结果表明，至少在目前的实验条件下，对流冷却以及辐射和火焰拉伸效应，而不是湍流混合，是流动湍流影响蔓延火焰熄灭的主要因素。
An experimental study is presented of the influence of turbulence on the spread of flames over the surface of a solid combustible in a gas flow opposing the direction of flame propagation. The flow velocity and its turbulent intensity are varied to observe their effects on the flame spread rate over thick PMMA and thin filter paper sheets. Also observed is their effect on the conditions for flame extinction. The results show that for thick PMMA sheets the spread rate first increases and then decreases with increasing turbulent intensity. The presence of a maximum appears to be the result of the flow transition from laminar to turbulent that influences the heat transfer process from flame to fuel. Through interferometric photographs it is shown that the decrease of the spread rate with the turbulence intensity is primarily due to the convective cooling of the region near the flame front in conjunction with other less important mechanisms related to flame and surface radiation. For thin paper sheets the spread rate always decreases as the turbulence increases. The observed differences between the thick PMMA and the thin paper results are probably due to their differing mechanisms of heat transfer ahead of the flame. It is also found that extinction of the flame occurs at lower flow velocities for higher turbulence intensities. This result suggests that convective cooling together with radiation and flame stretching effects, and not turbulent mixing, are the major factors through which flow turbulence affects the extinction of a spreading flame, at least for the present experimental conditions.