Flame heights and fraction of stoichiometric air entrained for rectangular turbulent jet fires in a sub-atmospheric pressure
Flame heights and fraction of stoichiometric air entrained for rectangular turbulent jet fires in a sub-atmospheric pressure
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DOI：
10.1016/j.proci.2016.07.090
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发表时间：
2017
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影响因子：
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通讯作者：
L. Hu;Xiaochun Zhang;Xiaolei Zhang;K. Lu;Zunmeng Guo
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文献类型：
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作者：
L. Hu;Xiaochun Zhang;Xiaolei Zhang;K. Lu;Zunmeng Guo
本文研究了低于大气压下矩形湍流射流火灾的火焰高度和化学计量空气夹带分数（n，火焰高度相关的基本参数），文献中没有这方面的数据。综合实验是在自然负压（拉萨市，64 kPa）下通过长径比从 1:1 到 1:71 变化的矩形喷嘴进行的。采用Quintiere和Grove提出的在标准大气压下获得的统一公式来测量和关联火焰高度，同时解决了负压下重要参数norCf（反映火焰中的空气夹带量，因此是火焰高度关联的基础）的变化。结果发现：(a)负压下的火焰高度可以很好地逼近Quintiere和Grove提出的统一公式；然而，(b)负压下的相关参数Cfi比标准压力下的相关参数Cfi大(标准压力下的1.6倍)或较小(标准压力下的73％)。然后，根据夹带强度 (C1) 和火焰包络线随压降的变化，从理论上推导出低于大气压的相对变化。理论上推导出的这两个压力之间的比率 n(orCf) 与实验相关结果一致。然后，通过考虑相关参数的变化，提出的显式模型通常可以预测两种压力下的火焰高度。
This paper investigates the flame height and the fraction of stoichiometric air entrained (n,the basic parameter in flame heights correlation) for rectangular turbulent jet fires at sub-atmospheric pressure, for which no data are available in the literature. Comprehensive experiments are carried out in a naturally sub-atmospheric pressure (Lhasa city, 64 kPa) by rectangular nozzles whose aspect ratio varied from 1:1 to 1:71. The flame heights are measured and correlated by the unified formula suggested by Quintiere and Grove which was obtained at standard atmospheric pressure, meanwhile the change of the important parameter,norCf(reflecting air entrainment into flame and thus being basic in flame height correlation) in the sub-atmospheric pressure is addressed. It is found that: (a) the flame height in the sub-atmospheric pressure can be well approached by the unified formula suggested by Quintiere and Grove; however (b) the correlation parameterCfis larger (1.6 times that in standard pressure) or the value ofnis smaller (73% of that in standard pressure) in the sub-atmospheric pressure than that in the standard pressure. The relative change ofnat the sub-atmospheric pressure is then theoretically deduced from the change of entrainment strength (C1) and flame envelope along with pressure drop. The theoretically deduced ratio ofn(orCf) between these two pressures agrees with the experimentally correlated results. Then, by accounting for the changes of the correlation parameters, a proposed explicit model can generally predict the flame heights in both pressures.