Turbulent coagulation of micron and submicron particles in swirling flow

Coagulation of fine particles in turbulent swirling flow is investigated experimentally and numerically. First, different swirl producers are compared and helical blade is adopted due to its enhanced diffusion and convection in the radial direction. Then, study on structural parameters of helical blade is carried out, the result shows that smaller diameter of inner blades or shorter axial spacing between inner and outer blades can create better performance. Finally, research on the effect of operating parameters is conducted. The result implies that lower velocity or higher particle concentration helps improve coagulation performance, since diffusion and particle interaction are strongly affected by the turbulent two-phase flow field. The patterns of coagulation for micron and submicron particles are slightly different due to varied particle dynamics, specifically, breakup is an important factor for larger particles. Rising temperature has positive effect on coagulation of submicron particles because of enhanced thermal motions. Comparatively, the thermal effect is negligible for the micron particles. The study analyzed the mechanism behind turbulent coagulation in swirling flow, from which directions for optimal design are provided.