Experimental investigations of dust explosions in standard industrial testing equipment such as the MIKE3 minimum ignition energy (MIE) testing device are promising ways of producing fundamental insights into dust cloud ignitability. However, advanced experimental methods must be developed to characterize the dust cloud ignition and combustion behavior of various types of dust. In this work, high-speed broadband and species-specific chemiluminescence imaging diagnostics are implemented to explore similarities and differences between organic and metal powder ignition kernel development. A selected set of 600-mg niacin ($\varphi$ = 2.9) and aluminum ($\varphi$ = 1.6) powder samples were dispersed in the air and ignited using a high-voltage spark inside a standard MIKE3 device. The resulting broadband flame emission was recorded at 4 kHz using a high-speed camera for the first 10 ms after the spark. For the niacin sample, species-specific chemiluminescence emissions from excited-state hydroxyl (OH*) and methylidyne (CH*) radicals were also recorded at 4 kHz and 1 kHz, respectively. The flame kernel in each image frame was detected using an intensity thresholding algorithm and tracked throughout the video sequence, yielding quantitative size, position, and velocity measurements of the evolving flame kernel during the first 10 ms after the ignition spark. For the niacin sample, a continuous and non-uniform reaction zone composed of burning particle clusters and excited-state radicals was observed. The niacin flame kernels grew from 5 mm to 17 mm with an initial velocity of 5 m/s. Conversely, an intensely bright reaction zone and discrete burning particles near the flame kernel boundary were observed in the aluminum sample. The aluminum flame kernels grew from 7 mm to 10 mm with an initial velocity of 3 m/s. The niacin and aluminum flame kernels traveled 7–11 mm away from the central spark gap and slowed down to 1 m/s by the end of the 10-ms period. This time-resolved imaging study, when coupled with previously reported three-dimensional particle and flow field data prior to the arrival of the ignition spark, sets the foundation for an improved multi-physics understanding of the initiation of dust cloud ignition and explosion processes.

在标准工业测试设备（例如 MIKE3 最小点火能量 (MIE) 测试设备）中进行粉尘爆炸的实验研究是对粉尘云可燃性产生基本见解的有希望的方法。然而，必须开发先进的实验方法来表征各种类型粉尘的粉尘云点火和燃烧行为。在这项工作中，实施了高速宽带和物种特异性化学发光成像诊断，以探索有机和金属粉末点火内核开发之间的异同。一组选定的 600 毫克烟酸 ($\phi$= 2.9) 和铝 ($\phi$= 1.6) 粉末样品分散在空气中，并使用标准 MIKE3 设备内的高压火花点燃。在火花发生后的前 10 毫秒，使用高速摄像机以 4 kHz 记录由此产生的宽带火焰发射。对于烟酸样品，激发态羟基 (OH*) 和亚甲基 (CH*) 自由基的物种特异性化学发光发射也分别在 4 kHz 和 1 kHz 下记录。使用强度阈值算法检测每个图像帧中的火焰内核，并在整个视频序列中进行跟踪，从而在点火火花后的前 10 毫秒内对演化的火焰内核进行量化大小、位置和速度测量. 对于烟酸样品，观察到由燃烧粒子簇和激发态自由基组成的连续且不均匀的反应区。烟酸火焰核以初始速度从 5 mm 增长到 17 mm5米/秒。相反，在铝样品中观察到强烈明亮的反应区和靠近火焰内核边界的离散燃烧颗粒。铝火焰内核以 3 m/s 的初始速度从 7 mm 增长到 10 mm。烟酸和铝火焰核从中心火花隙移动了 7-11 毫米，并在 10 毫秒周期结束时减慢到 1 米/秒。这项时间分辨成像研究与之前报道的点火火花到达之前的三维粒子和流场数据相结合，为改进对粉尘云点火和爆炸过程的起始的多物理场理解奠定了基础。