Effect of Varying Internal Geometry on the Near-Field Spray Characteristics of a Swirl Burst Injector

Clean and efficient combustion of liquid fuels depends on spray fineness that aids fast fuel vaporization and better fuel–air mixing. Swirl-burst (SB) atomizers generate fine droplets at the injector exit rather than typical jet cores as seen in the conventional atomizers. It integrates the primary breakup by bubble bursting of the Flow Blurring (FB) atomization, and secondary atomization by Rayleigh–Taylor instabilities between the swirling atomizing air and liquid phase. Thus, SB atomization has achieved clean lean-premixed flames of fuels with distinct properties involving diesel and straight oils around fifteen times more viscous. This study gains insights into the effect of the varying internal geometry, H/D ratio, on the atomization process and quantitatively investigates these effects on the near-field spray characteristics of SB injectors using high-spatial-resolution Shadowgraph Imaging Technique (SIT) and particle image velocimetry (PIV) for water sprays. Results acquired by SIT show that the Sauter Mean Diameter (SMD) of the droplets decrease with the reducing H/D ratio. The PIV measurements quantitatively reveal that atomization completion length decreases as the H/D ratio is lowered. Weber number analysis signifies that mostly vibrational and occasionally bag breakup dominates the secondary atomization for all the three H/D ratios. Results also reveal the high scalability of SB concept and its doubled atomization efficiency compared to FB injection.

Graphical Abstract