Gravity Effects on the Minimum Explosive Concentrations in 1-D Dust Explosion
Gravity Effects on the Minimum Explosive Concentrations in 1-D Dust Explosion
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DOI：
10.1080/00102202.2023.2182203
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发表时间：
2023-02
影响因子：
1.9
通讯作者：
K. Kuwana;S. Yazaki;Wookyung Kim;T. Mogi;R. Dobashi
中科院分区：
文献类型：
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作者：
K. Kuwana;S. Yazaki;Wookyung Kim;T. Mogi;R. Dobashi
摘要 粉尘爆炸特性的理论预测，例如最低爆炸浓度（MEC），有助于提高定量风险评估的准确性。本文提出了模拟一维尘云燃烧的连续介质模型。研究发现，热膨胀对灰尘的稀释降低了燃烧波通过灰尘云的传播速度。同时，由于弛豫时间导致的粒子速度增加的延迟抵消了稀释效应。因此，忽略弛豫时间会导致传播速度的低估。在没有热损失的情况下，当绝热燃烧温度降低到着火温度时，就会发生熄火；在这种情况下，MEC 与颗粒尺寸无关。另一方面，由于存在热损失，粉尘浓度较高时会发生消光； MEC 随着颗粒尺寸的增加而增加。准确评估着火温度是定量预测MEC的关键。特别关注重力效应，反映了最近为在不受重力影响的情况下获得传播机制的基本见解而进行的实验努力。在向上传播时，颗粒落向反应前沿，增强燃烧并提高传播速度。向下传播的情况则相反，当重力水平超过临界值时就会发生灭绝。在向上传播过程中，由于重力的影响，MEC 会随着粒径的增大而减小。
ABSTRACT Theoretical predictions of dust-explosion characteristics, such as the minimum explosive concentration (MEC), can help improve the accuracy of quantitative risk assessment. This paper presents a continuum model to simulate one-dimensional dust-cloud combustion. It is found that the dilution of dust by thermal expansion reduces the propagation speed of a combustion wave through a dust cloud. At the same time, the delay in the increase of particle velocity due to relaxation time counteracts the dilution effect. Therefore, neglecting the relaxation time results in the underestimation of propagation speed. In the absence of heat loss, extinction occurs when the adiabatic combustion temperature decreases to the ignition temperature; MEC is independent of particle size in such cases. With the presence of heat loss, on the other hand, extinction occurs at a higher dust concentration; MEC increases with particle size. Accurate evaluation of ignition temperature is key to the quantitative prediction of MEC. A particular focus is given to gravity effects, reflecting recent experimental efforts to obtain fundamental insights into propagation mechanisms without being affected by gravity. In upward propagation, particles fall toward the reaction front, enhancing combustion and increasing the propagation speed. The situation in downward propagation is the opposite, and extinction occurs when the gravity level is beyond a critical value. In upward propagation, MEC can decrease with an increase in particle size, owing to the influence of gravity.