The dust lifting mechanism and dust flame propagation modelling

在地下采煤或硫化铁作业以及许多工业设施中，可燃粉尘层积聚在地板、水平壁架、机器表面和假天花板上方。粉尘层可以很容易地被微弱的爆炸或压力波提升到悬浮状态。典型原因的一些例子是地下矿井中的小型甲烷气体爆炸，硫化物矿井作业中爆炸物的冲击波，清洁作业，加工厂中打开的窗户或门引起的强风，或压缩气体系统的泄漏。一旦形成粉尘云，总是有很高的可能性点燃，导致闪光或传播粉尘爆炸。此外，如果尘埃云是在一个包含障碍物的有限空间内形成的，则传播的尘埃火焰将加速，可能导致尘埃到爆炸的转变。因此，本研究计划的重点是了解和模拟粉尘提升过程。总体长期目标是更好地预测粉尘爆炸危险，从而制定战略，防止其发生或减轻其后果。该实验方案将研究粉尘提升的机制，作为颗粒性质（密度、类型和形状）、粉尘层厚度、颗粒大小分布、冲击波传播速度和障碍物存在的函数。一些实验将在标准的20升粉尘爆炸室中进行，以更好地了解目前尚不清楚的非标准粉尘（例如低密度纤维素纤维）的分散情况。此外，在一个专门建造的激波管实验将允许高速纹影摄影的灰尘提升过程的可视化。所有这些实验将使开发一个合适的模型来描述粉尘提升，分散和混合过程中实施的粉尘爆炸模拟代码。该模拟代码将允许从各种粉尘的标准测试中预测爆炸特性，以及预测工艺设备和设施内的粉尘爆炸危险。

In underground coal mining or iron sulfide operations as well as many industrial facilities, combustible dust layers accumulate on floors, horizontal ledges, surfaces of machinery, and above false ceilings. Dust layers can easily be lifted into suspension by weak explosions or pressure waves. Some examples of typical causes are a small methane gas explosion in an underground mine, the blast wave from an explosive charge in a sulfide mine operation, cleaning operations, a strong gust of wind because of an open window or door in a processing plant, or a leak from a compressed gas system. Once a dust cloud is created, there is always a high probability of ignition leading to a flash fire or a propagating dust explosion. Furthermore, if the dust cloud is formed within a confined space that contains obstacles, the propagating dust flame will accelerate, possibly leading to a dust-to-detonation transition. Therefore, this research program focuses on understanding and modelling the dust lifting process. The overall long-term objective is to better predict the dust explosion hazard and thereby develop strategies to prevent them from occurring or to mitigate their consequences. The experimental program will investigate the mechanism of dust lifting as a function of the nature of the particles (density, type and shape), thickness of the dust layer, particle size distribution; shock wave propagation velocity; and presence of obstacles. Some experiments will be done in a standard 20-L dust explosion chamber to better understand the dispersion of non-standard dusts (e.g. low density cellulosic fibers) which are currently not well-understood. Additionally, experiments in a purpose built shock tube will allow high-speed Schlieren photography for visualization of the dust lifting process. All these experiments will enable development of a suitable model to describe the dust lifting, dispersion, and mixing process for implementation in a Dust Explosion Simulation Code. This simulation code will allow prediction of explosibility characteristics from standard testing of various dusts as well as prediction of the dust explosion hazard within process equipment and facilities.