Experimental investigation of the spray characteristics for air-less nozzle, internal-mix nozzle and external-mix nozzle

Spray technology has a widely application in all kinds of industrial field, it is important to investigate the spray characteristics of different nozzles which have a decisive effect on spray area. In this study, Phase Doppler Analyzer is used to measure and compare the spray characteristics of air-less nozzle, internal-mix nozzle and external-mix nozzle under different injection conditions. The results show that the increase of compressed air pressure reduces the SMD of air-assisted spray. The uniformity of the droplets size distribution of internal-mix nozzle is also improved by higher compressed air pressure, while that of external-mix nozzle deteriorates. As the axial distance increases, the Sauter Mean Diameter and uniformity index of all nozzles decrease first and then increase due to the collisions and coalescence of droplets. As the radial distance increases, the Sauter Mean Diameter of spray for the air-less nozzle and internal-mix nozzle decreases, and the uniformity index increases. While the change of the Sauter Mean Diameter and uniformity index for the external-mix nozzle are opposite because air and droplets interact intensely.