Abstract The coal devolatilization plays a significant role in the combustion of pulverized coal particles. The evolution of volatile cloud during devolatilization of pulverized coal particles (105–125 μm) is studied in a high-temperature flat-flame burner by combining high-speed photography with high-speed digital inline holography (DIH). By the high-speed holographic visualization, the evolution of volatile cloud of pulverized coal from volatile release to soot aggregation generation can be divided into four stages. Effects of coal type on volatile cloud evolution are investigated using three different coals, i.e., Shanxi bituminous coal, Ximeng lignite and Yinni lignite. The results show that both the Shanxi bituminous coal and Ximeng lignite produce soot aggregation during devolatilization, which is rarely observed for Yinni lignite. Moreover, Shanxi bituminous coal has a higher potential in soot cluster formation for its higher coal rank than Ximeng lignite. The high-speed reconstructed image sequences are analyzed to measure the velocity slip between the parent particle and volatile cloud. Compared with Shanxi bituminous coal, Ximeng lignite exhibits a larger slip velocity. This work also demonstrates that high-speed DIH has the powerful capacity of directly observing the evolution of volatile cloud, and helps to gain a deep understanding of pulverized coal combustion.

中文翻译：

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高速数字在线全息可视化煤粉燃烧中挥发性云的演变

摘要 煤的脱挥发分在煤粉颗粒的燃烧过程中起着重要的作用。通过将高速摄影与高速数字在线全息 (DIH) 相结合，在高温平焰燃烧器中研究了煤粉颗粒 (105-125 μm) 脱挥过程中挥发性云的演变。通过高速全息可视化，煤粉挥发物云从挥发物释放到烟尘聚集的演变可分为四个阶段。使用三种不同的煤，即山西烟煤、西盟褐煤和银泥褐煤，研究了煤类型对挥发云演化的影响。结果表明，山西烟煤和西盟褐煤在脱挥发分过程中都会产生烟尘聚集，这在银泥褐煤中很少观察到。而且，山西烟煤的煤级高于西盟褐煤，因此在形成烟尘簇方面具有更高的潜力。分析高速重建的图像序列以测量母粒子和挥发性云之间的速度滑移。与山西烟煤相比，西盟褐煤表现出更大的滑移速度。这项工作也证明了高速DIH具有直接观测挥发性云演化的强大能力，有助于深入了解煤粉燃烧。西盟褐煤表现出较大的滑移速度。这项工作也证明了高速DIH具有直接观测挥发性云演化的强大能力，有助于深入了解煤粉燃烧。西盟褐煤表现出较大的滑移速度。这项工作也证明了高速DIH具有直接观测挥发性云演化的强大能力，有助于深入了解煤粉燃烧。