Experimental Analysis Of Spatial Evolution Of Mean Droplet Diameters In Effervescent Sprays

Effervescent atomization has established itself in the past decade as a promising alternative to conventional spray formation mechanisms. A great effort is currently being put into understanding the involved phenomena and developing numerical models to predict outcomes of processes relying on effervescent atomizers (i.e. spray combustion, coating, drying). This still proves to be a formidable challenge as effervescent atomization is a complex process involving two phase flow.The presented paper focuses on mean droplet sizes and how they vary throughout effervescent sprays at different operating conditions. The experiment was performed using Phase Doppler Anemometry (PDA) and the droplet data were collected in multiple locations varying both axially and radially. At each measurement location the Sauter Mean Diameter (SMD) was computed. The preliminary results show that closer to the spray nozzle the bigger droplets are concentrated in the spray core, while the small droplets are in the peripheral regions. However, this trend is slowly reversing with increasing distance from the spray nozzle. Finally, from a certain distance the initial trend is completely reversed with the small droplets being in the spray core, while larger droplets are found closer to the edge of the spray. Moreover, this phenomenon seems to be independent of operating conditions. Reasons for such behaviour are suggested and discussed. Furthermore, SMD sensitivity to operating conditions is analysed.