Investigation of mixing flow field of spray droplets in crossflow

In order to understand the evolution and mechanism of the mixing of spray droplets in crossflow in confined space, the mixing flow fields of water spray in air crossflow were measured in a rectangular duct by using a particle image velocimetry (PIV) system. The spray was generated by a pressure swirl nozzle. The velocity vector structures at different cross sections were obtained under the work conditions of three nozzle injection angles and three liquid/gas momentum flux ratios. The results show that the leading vortex pair appears due to the first impingement of the crossflow and the spray. The counter-rotating vortex pairs (CVPs) are observed during the mixing process. The CVP forms due to the shear of spray and the restraint of wall and plays an important role in influencing the mixing uniformity. It is also found that the inclined nozzle with an injection angle against the upstream crossflow allows the CVP to occur early and the CVP maintains a small size. A smaller liquid/gas momentum flux ratio also contributes to a small-scale CVP. Both the two mechanisms help to enhance the mixing uniformity.