Box-Behnken design application to optimize swirl effervescent droplet mean diameter

Swirl effervescent atomization combines the principles of swirling and bubbling liquids to create a wider spray pattern while using less liquid than traditional methods. The diameter of the resulting droplets, a key feature in atomization performance, is influenced by various dimensionless numbers such as the gas-to-liquid ratio and the Reynolds number. A design of experiments approach was used instead of the traditional one-factor-at-a-time testing to study these factors efficiently. A novel swirl effervescent atomizer was fabricated. Shadowgraph was used to capture droplet images and image processing was used to analyze the droplet diameter. The increase of the liquid Reynolds number from 847 to 2540 causes the Sauter mean diameter to decrease. The increase of gas Reynolds number from 0 to 1514 caused a decrease in the Sauter mean diameter. Increasing the swirl chamber length to discharge orifice diameter ratio causes an increase in Sauter mean diameter. A mathematical model was proposed and satisfies the goodness-of-fit in regression and ANOVA. It was discovered that significant impacts on the droplet mean diameter were exerted by changes in the gas and liquid Reynold numbers but the steeper reduction of the Sauter mean diameter was observed with the change of gas Reynolds number. Meanwhile, minimal effect was found to be exerted by the swirl chamber length to discharge orifice diameter ratio. The results show that the developed mathematical model can accurately predict the correlation of the Sauter mean diameter with the aforementioned factor.