甲烷浓度对PMMA/甲烷混合爆炸下限及预热区厚度的影响

为探索甲烷体积分数对聚甲基丙烯酸甲酯（polymethyl methacrylate，PMMA）/甲烷混合爆炸下限及预热区厚度的影响，采用半封闭可视化实验装置研究甲烷/PMMA粉尘混合爆炸火焰传播过程。结果发现，随着甲烷体积分数增加，平均粒径为28和54 μm的粉尘爆炸下限逐渐降低，平均粒径为54 μm的粉尘混合爆炸预热区厚度增大，28 μm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；28 μm粉尘混合爆炸的预热区厚度不变表明28 μm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，在甲烷体积分数相同时，粉尘质量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，粉尘质量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。

Effect of methane concentration on minimum concentration and thickness of preheating zone in PMMA/methane hybrid explosion

To explore the effects of methane concentration on the minimum explosible concentration and the thickness of preheating zone of polymethyl methacrylate (PMMA)/methane hybrid explosions, we investigated the flame propagations of methane/PMMA hybrid explosions in a semi-closed visualization experimental apparatus. The results showed that the minimum explosible concentration of the dusts with the average particle size of 28 μm and 54 μm decreased with the increase in the methane concentration. This could be attributed to the synergistic effect of methane and PMMA particles, which allowed the explosion of the combustible gases pyrolyzed/volatilized by PMMA particles at a lower concentration. It was also observed that the thickness of the preheating zone of the 54 μm dust increased as the methane concentration increased, while the thickness of the preheating zone of the 28 μm dust did not change remarkably. It was inferred that the 28 μm PMMA particles pyrolyzed/volatilized completely to form a homogeneous preheating zone with methane. Moreover, the flame propagation velocity increased as did the dust concentration with the same methane concentration. Meanwhile, the flame propagation velocity fluctuated with the increase of the methane concentration when the equivalence ratios were approximately the same.