Analysis and research on spray acoustics characteristics of an effervescent atomizer

The phenomenon of bubble expansion and explosion downstream of the atomizer orifice is primarily responsible for the atomization of liquid into droplets. However, experimental validation of the effervescent atomization mechanism has proven elusive due to challenges posed by high flow density, elevated flow rates, small bubble sizes, and short bubble lifetimes. In this study, both theoretical and experimental analyses were conducted to investigate the far-field acoustics of gas jets, liquid jets, and gas-liquid two-phase sprays. A noise analyzer was employed to measure the acoustic emissions generated by these three configurations: gas jets, liquid jets, and gas-liquid mixed jets (i.e., effervescent atomization). A flow state model was established based on global noise characteristics within the acoustic modal domain. The theoretical analysis included quantifying bubble populations downstream of the atomizer outlet and aggregating noise resulting from bubble cluster collapse. The results indicate that effervescent atomization noise increases with increasing mixing chamber pressure but decreases as the gas void fraction rises. Meanwhile, the noise exhibited fluctuations in response to variations of the internal two-phase flow pattern. The presence of numerous micro-bubbles collapsing downstream of the orifice was confirmed. It was noted that the noise of the two-phase spray does not simply represent a superposition of noise from gas and liquid jets; rather, it is a composite superposition of multiple sources, including gas jet noise, liquid jet noise, and bubble rupture noise. This study provides significant theoretical insight and practical implications for the field of effervescent atomization.