Exposure to the Role of Primary Breakup Parameters of an Effervescent Atomizer Using High‐Speed Flow Visualization Techniques

ABSTRACT The study experimentally investigates the primary disintegration of a liquid sheet in an inside‐out effervescent atomizer using high‐speed flow visualization, focusing on the effects of bubbly flow. Key stability parameters, such as breakup length and frequencies, were analyzed in the Rayleigh zone (We g < 0.4) and the first wind‐induced regime (0.4 < We g < 5.4). For low gas Weber numbers, the disintegration process exhibited prolonged primary breakup events and shorter intermediate breakups. The coexistence of sinusoidal and dilatational modes of interfacial instability and their roles in these breakup processes were also examined. Increasing the gas Weber number promoted continuous bubble formation, eliminating intermediate breakup events and dilatational modes, thereby enhancing primary breakup efficiency. In the Rayleigh zone, liquid sheet disintegration is primarily driven by the liquid's inherent momentum. However, as gas velocities increase (We g > 0.4), the momentum of the gas bubbles becomes dominant. A gas‐to‐liquid momentum ratio, which accounts for the effective area of aeration holes where gas mixes with the co‐flowing liquid, was introduced. This ratio, replacing the traditional gas‐to‐liquid ratio, better captures the initial flow dynamics at the nozzle exit. Dimensionless stability characteristics plotted against this ratio enable data collapse and yield universal functions. Notably, a stronger correlation for breakup frequencies and disintegration length was achieved in the first wind‐induced zone compared to the Rayleigh zone, owing to the effective gas momentum. Though the Rayleigh zone generally results in larger droplets, the size can be fine‐tuned by modifying parameters like liquid viscosity, surface tension, and the gas‐to‐liquid ratio. This provides flexibility to tailor the atomization process to specific application needs. Additionally, integrating the Rayleigh zone with other regimes, such as wind‐induced breakup, can enable the development of hybrid atomization systems that achieve an optimal balance between energy efficiency and finer droplet size distributions.