Promotion of particle agglomeration by different vortex generator angles based on PIV-PDPA experiment

Abstract

Turbulent agglomeration is a promising pretreatment technology aimed at enhancing fine particles removal efficiency. Recent studies suggested that V-structure vortex generators are effective in improving turbulence to promote particle collisions and size increase. However, the experimental studies on flow fields and particles induced by V-structure vortex generators with different angles are still insufficient. To this end, this study investigated the effect of the angle of V-structure vortex generators on particle agglomeration based on the experimental approach. More specifically, the flow field dynamics were obtained directly from a Particle Image Velocimetry, while the particle behavior and size variation were investigated by a Phase Doppler Particle Analyzer. The results of the Phase Doppler Particle Analyzer showed that the addition of the vortex generator and its angle increase led to an increase in average size as well as cross-particle size, while a decrease in number concentration of smaller particles, which confirmed the collisions between smaller particles. Through Particle Image Velocimetry experiments, it was found that a wider range of recirculation regions and counter-rotating eddies were generated. Furthermore, by analyzing particle distribution and tracking single particle trajectory through numerical simulation, two kinds of agglomeration mechanisms were proposed. One being the trajectory crossover of smaller particles triggered by recirculating vortex, and the other is the preferential concentration of larger particles. The results of this study can provide a theoretical basis for the design of V-structure vortex generators and particle agglomeration techniques.