Particle dynamics investigation by means of shadow imaging inside an air separator

Abstract

A multicamera shadow imaging (shadowgraphy) system is developed to simultaneously capture particle dynamics at multiple locations inside a so called zigzag air separator which is used for separating fine from coarse particle fractions. The adaption of the shadowgraphy system to the specific requirements of the separator apparatus to measure particle sizes and velocities including calibration and particle size correction strategies is described. Measurements reveal the behaviour of glass beads ranging from 1 to 4 mm in diameter with variable particle mass loadings and air flow rates inside the zigzag channel. From the processing of the shadow data, particle flow morphologies and characteristic particle trajectories inside the channel stages are obtained. Furthermore, it is shown that particle mean velocities and particle fluctuation energies depend on the particle mass loading, the air flow rate and the location inside the zigzag channel. The results reveal novel quantitative insights into particle velocities in such an air separator which can be used to better understand the underlying particle mechanisms and foster the development of refined process models.