One of the more obvious consequences of a dust deflagration inside process equipment or a structure is the mechanical damage caused by shock (compression) waves. This overpressure damage is revealed through the displacement of equipment, the outward deformation or rupture of enclosures constructed of ductile materials, or the projection of missiles. However, a different type of damage is sometimes observed in the ductwork connecting process equipment. In particular, the ductwork is collapsed as if it were subjected to an external, rather than an internal pressure. The phenomenon that causes this collapse of thin-walled conduit is a gas dynamic process called an expansion wave. When a dust deflagration travels through a conduit, it accelerates and causes a rise in pressure. When the dust deflagration is vented (say through a deflagration vent), the discharge of the high-pressure combustion products causes the formation of an expansion wave that travels in the reverse direction of the original discharge. The expansion wave causes the pressure in the ductwork to fall below atmospheric pressure. The sub-atmospheric pressure, in turn, causes the ductwork to fail by buckling. In this study, we examine the gas dynamics of the expansion wave, demonstrate how to calculate the degree of pressure drop caused by the expansion wave, and illustrate the concept with case studies of dust explosions.

过程设备或结构内部爆燃粉尘的最明显后果之一是冲击波（压缩）引起的机械损坏。这种超压损坏是通过设备的移位，由易延展材料制成的机壳的向外变形或破裂或导弹的投射而揭示出来的。但是，有时在连接工艺设备的管道系统中会发现不同类型的损坏。特别是，管道系统像是受到外部压力而不是受到内部压力的作用而塌陷。导致薄壁管​​道塌陷的现象是称为膨胀波的气体动力学过程。当粉尘爆燃通过导管传播时，它会加速并导致压力升高。放掉爆燃灰尘后（例如通过爆燃通风孔），高压燃烧产物的排放导致形成膨胀波，该膨胀波沿原始排放的相反方向传播。膨胀波使管道中的压力降到大气压以下。低于大气压又会导致管道系统因弯曲而失效。在这项研究中，我们研究了膨胀波的气体动力学，演示了如何计算由膨胀波引起的压降程度，并通过粉尘爆炸案例研究说明了这一概念。导致管道系统因弯曲而失效。在这项研究中，我们研究了膨胀波的气体动力学，演示了如何计算由膨胀波引起的压降程度，并通过粉尘爆炸案例研究说明了这一概念。导致管道系统因弯曲而失效。在这项研究中，我们研究了膨胀波的气体动力学，演示了如何计算由膨胀波引起的压降程度，并通过粉尘爆炸案例研究说明了这一概念。