Effects of particle size distributions on PMMA dust flame propagation behaviors
Effects of particle size distributions on PMMA dust flame propagation behaviors
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DOI：
10.1016/j.powtec.2017.05.001
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发表时间：
2017-07
影响因子：
5.2
通讯作者：
Xinyan Zhang;Jianliang Yu;W. Gao;Dawei Zhang;Jinhua Sun;Song Guo;R. Dobashi
中科院分区：
文献类型：
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作者：
Xinyan Zhang;Jianliang Yu;W. Gao;Dawei Zhang;Jinhua Sun;Song Guo;R. Dobashi
对具有相同Sauter直径的聚甲基丙烯酸甲酯（PMMA）粉尘云进行了实验研究，以揭示粒径分布对PMMA粉尘火焰传播行为的影响。采用高速摄影技术对火焰传播过程和微观结构进行了捕捉。结果表明，不同质量分数的100 nm、5 μm和30 μm PMMA粉尘云的燃烧行为较为复杂。火焰的宏观发展是由主要质量比例的粉尘颗粒决定的。小粒径PMMA粉尘的比例越大，火焰阵面越光滑，脉动火焰传播速度越快。火焰温度由直径为25 μ m的Pt-Pt/Rh 13%丝组成的细热电偶检测。火焰传播速度越快，火焰最高温度越高。混合物B和E尘埃云的最高温度可以维持较长的时间，这是由于较小颗粒的质量分数较大。混合气尘云的热转换过程主要受外部热源的控制，包括燃烧区的辐射和颗粒与气体之间的对流换热。热解/挥发分控制了整个混合物的B-E粉尘云燃烧过程。混合物的火焰与小颗粒的预混气体火焰耦合，团聚体的扩散火焰伴随着分裂团聚体周围的局部预混火焰，以及扩散火焰伴随着大颗粒的高热解物浓度区域的局部预混火焰。燃烧机理取决于占主导地位的质量分数粉尘颗粒。小颗粒不仅加速了火焰传播，而且影响了火焰结构和燃烧机理。
Experiments of polymethyl methacrylate (PMMA) dust clouds with same Sauter diameters were conducted to reveal the effects of particles size distributions on PMMA dust flame propagation behaviors. High-speed photography was used to capture the flame propagation behaviors and microstructures. The results showed that the combustion behaviors of PMMA dust clouds with different mass fractions of 100 nm, 5 μm and 30 μm PMMA dust particles were complicated. The macroscopical developments of the flames were determined by the major mass proportion dust particles. The flame front became smoother and the average pulsating flame propagation velocity was faster with more proportion of smaller PMMA dust particles. The flame temperatures were detected by a fine thermocouple comprising 25 μm-diameter Pt-Pt/Rh13% wires. It was found that the faster the flame propagated, the higher maximum flame temperature was. The maximum temperatures of mixture B and E dust clouds could maintain longer time due to the larger mass fractions of smaller particles. The thermal conversion processes of mixture A–E dust clouds were dominated by the external heat transfer sources, including radiation from burned region and heat convection between particles and gases. And pyrolysis/devolatilization controlled the overall mixture B–E dust clouds combustion processes. Flames of mixtures were coupled with the premixed gas flame of the smaller particles, the diffusion flame of the agglomerates accompanying local premixed flame around split agglomerates, and the diffusion flame accompanying local premixed flame in high pyrolyzates concentration areas of larger particles. The combustion mechanism was determined by the dominant mass fraction dust particles. Smaller particles not only accelerated flame propagation but influenced the flame structure and combustion mechanism.