A BASIC STUDY ON PREDICTING AND SENSING EXPLOSION HAZARDS IN PRODUCING AND HANDLING POWDERS CONSISTED OF SUPER FINE PARTICLES

对细颗粒和/或超细颗粒的爆炸危险性进行了基础研究。我们的研究由三部分组成。第1部分是关于粒子分散技术。我们设计开发了一种气动颗粒分散装置。分散的颗粒及其与气流的相互作用通过阴影成像可视化。第二部分测量了细颗粒和超细颗粒（煤粉、几种谷物粉和钨细颗粒）在激波加热空气中的点火延迟时间。实验温度范围（800 ~ 1260 K）内，颗粒云分散性较大，点火延迟时间较短。点燃颗粒的轨迹与分散的颗粒一起拍摄。研究发现，钨粉和煤粉都是单独而非集体点燃的，而且钨粉（超细颗粒云）的爆炸威力远大于普通粉末（细颗粒云）。在第三部分中，研究了爆炸波与地板上粉末层的相互作用与危害评估的关系。在这一层的底部检测到一个非常高的峰值压力。为了分析这一异常现象，研究了含尘表面上的倾斜冲击反射。利用楔形模型成功地模拟了粉末层上的冲击反射。结果表明，水槽的波结构是非定常的，水槽底部反射的整个波对水槽的波结构起着关键作用。

A basic study on explosion hazard of fine and/or super-fine particles has been carried out. Our study consists of three parts. Part 1 is related to particle dispersion technology. We have designed and developed a pneumatic particle dispersion device. Dispersed particles and their interaction with an airstream were visualized by shadowgraphy. In part 2, ignition delay times of fine and super-fine particles (pulverized coal, several kinds of cereal powder and tungsten fine-particle) have been measured in a shock heated air. The ignition delay time was less for particle cloud with larger dispersal within the temperature range (800 through 1260 K) of our experiment. Loci of ignited particles were photographed together with dispersed particles. It was found that tungsten particles as well as pulverized coal ignite as an individual rather than a group, and that the explosibility of tungsten powder(super fine particle cloud) is much larger than that of usual powder(fine particle cloud). In part 3, interaction of a blast wave with powder layer on a floor has been investigated in connection with hazard assessment. It was detected a very high peak pressure at the bottom of the layer. Oblique shock reflection over dusty surface has been investigated in order to analysis this abnormal phenomenon. Model wedges were successfully used to simulate shock reflection over powder layer. It was found that the wave structure is essentially unsteady and the entire waves reflected from the bottoms of gutters play a key role to the configuration.