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首页> 外文学位 >FLAME PROPAGATION DUE TO LAYERED COMBUSTIBLE DUST (EXPLOSIONS, PARTICULATES, HETEROGENEOUS, GRAIN).
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FLAME PROPAGATION DUE TO LAYERED COMBUSTIBLE DUST (EXPLOSIONS, PARTICULATES, HETEROGENEOUS, GRAIN).

机译：分层可燃粉尘引起的火焰传播（爆炸，微粒，异质，谷物）。

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Damaging dust explosions occur in grain elevators, coal mines, and other industrial facilities due to the presence of combustible layered dust and the subsequent combustion of the dust particles in air. This phenomenon has been investigated in the laboratory with emphasis on developing an understanding of the mechanisms involved so that these explosions may be prevented. The apparatus used consists of a 36 m long tube of 0.3 m diameter, closed at the ignition end and open at the opposite end. A primary explosion is initiated by dispersing dust in the first 3.6 m using air-jets and igniting the resulting cloud. This in turn initiates a secondary explosion which is an accelerating flame that entrains the layered dust in the rest of the tube as a result of the accompanying pressure waves. The flame trajectory and time histories of static pressure, gas velocity, gas temperature, particle temperature, and dispersed dust concentration have been recorded at different tube locations and analyzed.; Among the dusts tested, corn starch and mixed grain dust are found to be more reactive, resulting in flame velocities of about 600 m/sec and overpressures of about 6 atm under dry conditions. Increasing the dust moisture content to 9% suppresses dust entrainment and reduces the above values to about 120 m/sec and 1.3 atm, respectively. Thin layers are found to be more conducive to flame propagation than thick layers at a given mass loading. Flame propagation limits are obtained for different layer thicknesses. Prior to this work there has been little quantitative data relating to secondary dust explosions. Large particles (over 425 (mu)m), contrary to existing data, are found to sustain secondary explosions under certain conditions. Dust entrainment and the increase in burning velocity due to turbulence are found to be the most important parameters governing the secondary explosion development.; The one-dimensional, unsteady, compressible flow equations have been solved numerically using an available code to model the combustion process occurring in the experiments. The flame is modeled as a discontinuity, characterized completely by the specified burning velocity and density expansion ratio. The calculated results are in reasonable agreement with the measured results.
机译：由于可燃的分层粉尘的存在以及随后空气中粉尘颗粒的燃烧，在谷物升降机，煤矿和其他工业设施中发生了有害的粉尘爆炸。已经在实验室对这种现象进行了研究，重点是发展对所涉及机制的理解，以便可以防止这些爆炸。所使用的设备由36 m长，直径为0.3 m的管组成，在点火端关闭，在另一端打开。通过使用喷气机将灰尘分散在前3.6 m中并点燃产生的云，从而引发一次爆炸。反过来，这会引发二次爆炸，这是一种加速火焰，由于伴随的压力波，这种火焰将层状粉尘夹带在管的其余部分中。在不同的管子位置记录并分析了火焰轨迹和静压，气体速度，气体温度，颗粒温度以及分散的粉尘浓度的时间历程。在测试的粉尘中，发现玉米淀粉和混合谷物粉尘具有更高的反应活性，在干燥条件下，火焰速度约为600 m / sec，超压约为6 atm。将粉尘的水分含量提高到9％可以抑制粉尘的夹带并将上述值分别降低到约120 m / sec和1.3 atm。在给定的质量负载下，薄层比厚层更有利于火焰传播。获得不同层厚度的火焰传播极限。在这项工作之前，很少有关于二次粉尘爆炸的定量数据。与现有数据相反，发现大颗粒（超过425μm）在某些条件下可承受二次爆炸。尘埃夹带和湍流引起的燃烧速度的增加是控制二次爆炸发展的最重要参数。使用可用代码对实验中发生的燃烧过程进行建模，可以对一维非定常可压缩流动方程进行数值求解。火焰建模为不连续性，完全以指定的燃烧速度和密度膨胀比为特征。计算结果与测量结果合理吻合。

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