Abstract Hot-zone boilover is dangerous in crude oil tank fires. Previous investigations have experimentally shown that floating objects can suppress hot-zone boilover with small scale pool fires, but not indicate a clear suppression mechanism. Thus, this study uses floating perlites (0, 1 and 2 layers) on large scale pool fires to examine the mechanism by performing three series of experiments. The first series applies perlites to 1m-diameter crude oil fires to evaluate the effect of perlites on the hot-zone formation; the second investigates the effect of perlites on heat release rate (HRR) and combustion efficiency, and the third studies the blockage effect of perlites on radiation heat feedback. Experimental results show that the perlites can significantly delay the hot-zone formation, and suppress boilover. Accordingly, this study presents a hypothesis to explain the mechanism of suppressing boilover by floating objects. The perlites form a heat blockage layer decreasing the radiation feedback, and act as a nucleation site, leading to local vigorous boiling. The enhanced local nucleation increases the fuel vapor generation, and further enhances the blockage effect. The perlites consequently raise the fuel regression rate, and decrease the heat transfer to the deep fuel and water, decreasing the hot-zone formation rate.

中文翻译：

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在原油罐火灾中使用漂浮物抑制热区沸腾

摘要 原油储罐火灾中的热区沸腾是危险的。先前的研究已经通过实验表明漂浮物可以抑制小规模水池火灾的热区沸腾，但没有表明明确的抑制机制。因此，本研究在大规模水池火灾中使用漂浮珍珠岩（0、1 和 2 层）来通过三个系列的实验来检查机制。第一个系列将珍珠岩应用于1m直径的原油火灾，以评估珍珠岩对热区地层的影响；第二个研究珍珠岩对热释放率（HRR）和燃烧效率的影响，第三个研究珍珠岩对辐射热反馈的阻塞效应。实验结果表明，珍珠岩能显着延缓热区形成，抑制沸腾。因此，本研究提出了一个假设来解释浮动物体抑制沸腾的机制。珍珠岩形成热阻挡层，减少辐射反馈，并作为成核位点，导致局部剧烈沸腾。增强的局部成核增加了燃料蒸汽的产生，并进一步增强了堵塞效果。珍珠岩因此提高了燃料回归率，减少了向深层燃料和水的传热，降低了热区形成率。