Measurements of particle velocity and concentration for dilute swirling gas-solid flow in a vertical pipe

Experimental studies concerning the characterization of a dilute swirling gas-solid flow were carried out in a vertical pipe with a height of 12 m and an inner diameter of 80 nun. Polyethylene pellets, with mean diameter of 3.2 mm, were used as test particles. The initial swirl number varied from 0.0 to 0.94, the mean gas velocity varied from 9 to 25 m/s, and the solid-gas ratio varied from 0.2 to 0.7. In this study, the particle velocity and concentration profiles were measured by the photographic image technique for both nonswirling (axial) and swirling gas-solid flows. It was found that the particle velocity of the swirling flow is lower than that of the axial flow in the range of high gas velocity; however, high particle velocity in the former flow can be obtained in the range of low gas velocity. The particle velocity profiles, on the other hand, were found to be nearly uniform in both the swirling and axial flows. The particle concentration profiles in the swirling flow exhibited symmetric distributions with respect to the pipe axis, and a higher particle concentration appeared in the vicinity of the wall located in the acceleration region.