Concurrent-Flow Flame Spread Over a Thin Solid in a Narrow Confined Space in Microgravity
Concurrent-Flow Flame Spread Over a Thin Solid in a Narrow Confined Space in Microgravity
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DOI：
10.1115/imece2019-11908
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发表时间：
2019-11
期刊：
影响因子：
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通讯作者：
Yanjun Li;Ya-Ting T. Liao;P. Ferkul
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文献类型：
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作者：
Yanjun Li;Ya-Ting T. Liao;P. Ferkul
本文通过数值模拟研究了火焰传播过程中火焰与墙体之间的空气动力学和热相互作用及其对火灾行为的影响。这是为了支持即将在国际空间站上进行的微重力实验。对于数值研究，三维瞬态计算流体动力学燃烧模型被用来模拟并流火焰蔓延在一个狭窄的流动管道中的薄固体样品。流道高度是主要参数。数值计算结果预测了一个熄灭的高度低于该火焰未能蔓延的流动管道。对于足够大于淬火高度的管道高度，火焰在样品完全消耗之前达到稳定的蔓延状态。火焰传播速率和稳态热解长度随流道高度的减小先增大后减小。详细的气体和固体的轮廓表明，流动约束的火焰传播过程中有竞争的影响。一方面，它在燃烧产生的热膨胀过程中加速流动，增强火焰。另一方面，增加流动限制减少了对火焰的氧气供应，并增加了对壁的传导热损失，这两者都削弱了火焰。这些竞争效应导致火焰传播速率随管道高度变化的上述非单调趋势。这项工作与即将进行的微重力实验有关，在这些实验中，将使用国际空间站上的一个小型流动管道在低速并流中燃烧扁平薄样品。平行于燃料样品安装两个挡板（样品两侧各一个），以有效降低流动管道的高度。在这项工作中的实验的概念和设置。
A numerical study is pursued to investigate the aerodynamics and thermal interactions between a spreading flame and the surrounding walls as well as their effects on fire behaviors. This is done in support of upcoming microgravity experiments aboard the International Space Station. For the numerical study, a three-dimensional transient Computational Fluid Dynamics combustion model is used to simulate concurrent-flow flame spread over a thin solid sample in a narrow flow duct. The height of the flow duct is the main parameter. The numerical results predict a quenching height for the flow duct below which the flame fails to spread. For duct heights sufficiently larger than the quenching height, the flame reaches a steady spreading state before the sample is fully consumed. The flame spread rate and the pyrolysis length at steady state first increase and then decrease when the flow duct height decreases. The detailed gas and solid profiles show that flow confinement has competing effects on the flame spread process. On one hand, it accelerates flow during thermal expansion from combustion, intensifying the flame. On the other hand, increasing flow confinement reduces the oxygen supply to the flame and increases conductive heat loss to the walls, both of which weaken the flame. These competing effects result in the aforementioned non-monotonic trend of flame spread rate as duct height varies. This work relates to upcoming microgravity experiments, in which flat thin samples will be burned in a low-speed concurrent flow using a small flow duct aboard the International Space Station. Two baffles will be installed parallel to the fuel sample (one on each side of the sample) to create an effective reduction in the height of the flow duct. The concept and setup of the experiments are presented in this work.