Mixing characteristics of hollow cone spray with confined crossflow

The dispersion and movement features of the hollow cone spray droplets in confined crossflow in a square duct were measured with PIV technology on a self-established cold mixing rig. The droplet dynamics and vortices structures induced in the confined mixing flow field were obtained. The droplet dispersion in the mixing process was mainly influenced by several large-scale vortex structures, such as the counter-rotating vortex pairs (CVPs). The CVPs had a greater centrifugal effect on droplet dispersion because of preferential concentration so the droplets tended to accumulate along the edges of vortex structures. The main parameters affecting the mixing, such as crossflow velocity, atomization pressure and size of spray droplets were discussed and the curves of relationship between them and the best mixing effect were established. The mixing for double nozzles was also investigated and the influences of different injection angles on the mixing were discussed. The results showed that the way to improve the mixing was to avoid the stable large-scale vortex structures which could lead to non-uniform droplet dispersion and concentrations in the mixing flow field by controlling local droplets' contribution and dispersion by convection. Mixing could be enhanced by turning the spray direction against the crossflow, increasing the nozzle number and choosing the appropriate crossflow velocity. The analytical approach and research findings have important practical significance for the mixing chamber design and performance improvement for relevant industrial applications.