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为探索甲烷浓度对聚甲基丙烯酸甲酯(PMMA)/甲烷混合爆炸下限及预热区厚度的影响,本文采用半封闭可视化实验装置研究了不同浓度甲烷/PMMA粉尘混合爆炸火焰传播过程。结果发现,随着甲烷浓度增加,28μm和54μm粉尘爆炸下限逐渐降低,54μm粉尘混合爆炸预热区厚度增大,28μm粉尘混合爆炸预热区厚度基本不变。爆炸下限的降低是由于甲烷与PMMA粉尘存在协同作用,使得PMMA粒子热解/挥发出较低浓度的可燃气时即可发生爆炸。28μm粉尘混合爆炸的预热区厚度不变表明28μm粒子在预热区中完全裂解气化与甲烷气体形成均相的气体预热区。此外,在甲烷浓度相同时,粉尘浓度的增加使得火焰传播速度增大。而在组合当量比一定的条件下,粉尘浓度的增加并未使得混合爆炸火焰传播速度增大,而是出现一定的波动变化。
In order to explore the influence of methane concentration on the lower limit of PMMA / methane explosion and the thickness of the preheating zone, the semi-closed visual experimental apparatus was used to study the propagation of methane / PMMA dust explosion explosion with different concentrations of methane. The results showed that with the increase of methane concentration, the lower limit of 28μm and 54μm dust explosion gradually decreased, the thickness of preheating zone of 54μm dust explosion increased, and the thickness of 28μm dust blasting did not change. The lower explosion limit is due to the synergistic effect of methane and PMMA dust, allowing PMMA particles to explode when pyrolyzed / volatilized to a lower concentration of combustible gas. The uniform thickness of the preheat zone of the 28μm dust mixed explosion indicates that the 28μm particles are completely pyrolyzed in the preheating zone and the gas preheating zone is homogeneous with methane gas. In addition, at the same methane concentration, an increase in dust concentration causes an increase in flame propagation velocity. However, under the condition of the combined equivalence ratio, the increase of the dust concentration did not increase the propagation speed of the mixed explosion flame, but a certain fluctuation.