Pool fire with varying ullage height is a common type of accident that occurs in industrial parks. This paper explores the ullage height effects on the burning rate and heat feedback in pool fires through the experimental and theoretical study. A series of experiments were conducted using heptane with four tray sizes and five ullage heights. The results show that, the burning rate initially decreases, then increases and finally decreases as the ullage height increases. These results are mainly dependent on the change of internal flame behavior and thus heat feedback mechanisms with increasing ullage height. In the small ullage height conditions, the convective heat feedback reduces substantially whereas the radiative one rises slightly. When the ullage height reaches to a certain value, the convective heat feedback suddenly increases because of the flame inside the tray. The radiative heat feedback decreases gradually as the ullage height increase continually, while the convective one becomes nearly constant. Based on these results, three regimes are identified in terms of the burning rate variation with heat feedback: (1) convection controlled, (2) convection-radiation controlled and (3) radiation controlled. The new controlling mechanism of the burning rate variation (with ullage height), as a further extension of the classic scaling model by Blinov and Khudyakov on the burning rate variation (with pool diameter), could lay a solid foundation for future studies of the other key parameters in tank fires.

中文翻译：

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空缺高度对池火燃烧速率和热反馈影响的实验研究


不同空缺高度的水池火灾是工业园区常见的事故类型，本文通过实验和理论研究探讨了空缺高度对水池火灾燃烧速率和热反馈的影响。使用具有四种托盘尺寸和五种空缺高度的庚烷进行了一系列实验。结果表明，随着空缺高度的增加，燃烧速率先减小，然后增大，最后减小。这些结果主要取决于内部火焰行为的变化，以及随着间隙高度增加的热反馈机制。在小空缺高度条件下，对流热反馈大幅减少，而辐射热反馈略有上升。当空缺高度达到一定值时，由于托盘内部有火焰，对流热反馈突然增加。随着空缺高度的不断增加，辐射热反馈逐渐减小，而对流热反馈则几乎恒定。基于这些结果，根据热反馈的燃烧速率变化确定了三种状态：（1）对流控制，（2）对流辐射控制和（3）辐射控制。新的燃烧速率变化（随空缺高度）的控制机制，作为Blinov和Khudyakov关于燃烧速率变化（随池直径）的经典尺度模型的进一步扩展，可以为未来其他研究奠定坚实的基础。坦克火灾的关键参数。