粉尘云形成过程的可视化研究方法

The Visualization Method for the Study of Dust Dispersion Process

摘要: 为深入认识粉尘云的分散行为，本文开发了基于改进Siwek 20 L测试系统的可视化装置；利用高速摄像系统和图像处理技术，获得了Siwek 20 L装置内镁粉颗粒在扬尘过程中粉尘云透光率随时间的变化，并结合粉尘云浓度的变化对透光率曲线进行了分析。研究表明本方法所获的透光率变化过程与粉尘实际浓度变化具有一致性，能有效辨识粉尘云的运动状态和时空分布特性；在扬尘阶段，透光率曲线随时间增加首先迅速下降继而稳态波动，直观反映了颗粒快速喷射形成粉尘云，且粉尘云形成初期湍动剧烈但平均浓度相对稳定的实际过程；扬尘完成后，湍流强度急剧衰减、颗粒不断沉降，粉尘云浓度随之降低，导致透光率曲线随之上升。相较于PRL光学粉尘探针法，该方法获得的透光率结果能更客观地反应扬尘过程中粉尘浓度的实际变化规律，为粉尘云运动过程的研究提供了新的手段。

Abstract: To gain an insight into the dust dispersion behaviors, a visualization device was developed based on a modified Siwek 20 L spherical chamber. By using high-speed camera and image processing technique, the evolution of dust cloud transmission was obtained during the dispersion process of magnesium particles. Comparative analysis shows that the transmission varies accordingly with the variation of dust cloud concentration, and through the transmission-time trace, the motion state and distribution uniformity of dust cloud can be clearly recognized. In the early stage of dust dispersion, the transmission trace decreases quickly with time because of the fast injection of dust particles, and then fluctuates rapidly with large but relatively stable amplitude, indicating that the dust cloud in the early stage is in a strongly turbulent state, so that all particles are suspended and the average concentration in the chamber is nearly constant. After early stage, the turbulence in-tensity attenuates rapidly and dust particles begin sediment, so that the transmission trace follows an increasing trend, indicating that actual concentration of dust cloud becomes steadily decreased. Compared with the PRL optical dust probe method, the current method can provide more objective transmission-time traces to characterize the variation of dust cloud in the dispersion process.