Experimental study of the mixing of two impinging pressure-swirl sprays in crossflow

Abstract

This paper discusses the results from an experimental study on the mixing of two impinging pressure-swirl sprays in the crossflow with the PIV visualization system and the image-processing techniques. The experiments were carried out inside a rectangular duct (95mm×95mm) at the ambient temperature and pressure. Five injection angles (α=60–120°, at 15° intervals from the negative direction of the crossflow) were experimented with the crossflow velocity range from Re=25,700 to Re=64,300. The droplet dispersion and its dependence on the spray injection angle and the crossflow velocity are examined. The large-scale vortex structures occurred are analyzed and their influence on the mean velocity, vorticity and turbulent characteristics of the droplet swarm are studied. The comparison is made with single-spray data of the previous studies. Double coherent structures are discovered and they greatly depend on the spray injection angle as that of single nozzle. When α<90°, the greater coherent structures occur and the droplet swarm turbulent intensity increase and hence, the droplet dispersion is promoted. When α=90°, the largest Counter-Rotating Vortex Pair (CVP) structure and the greatest entrained air flow are induced and compare with single nozzle the CVP structure becomes more enduring. Furthermore, the deposition of droplets at the bottom of the mixing duct is inhibited significantly when the second spray is introduced especially for α=60° and α=120°.