# Innovative Acoustic-Hydraulic Method for High-Performance Fine Liquid Atomization
## 5 Conclusions  
The development of new liquid atomization devices and methods that can produce a fine spray at high throughput is of significant interest for various technological applications. For example, high dispersion together with high productivity of aerosol creation are required in the technological processes of aerosol drying, aerosol coating, surface treatment, and spraying of drugs. In this study, we proposed and investigated a new design of an acoustic-hydraulic nozzle that combines the benefits of the hydraulic spray method (high productivity) and ultrasonic spraying (high droplet dispersion). The proposed theoretical model was validated through experimental data, and we identified critical conditions for intensity and pressure, which are the controlling parameters of the device. These conditions enable the implementation of the cavitation spray mode and achieve the desired process characteristics. Our results demonstrate that the proposed design can achieve droplet sizes of less than 50 microns with a productivity of about 5-10 mL/s at an exposure frequency of 22.5 kHz when creating conditions of cavitation spraying. Such a small droplet size at the used ultrasonic frequency of 22.5 kHz and the achieved spraying productivity is not attainable by either ultrasonic or hydraulic spraying methods separately, as demonstrated theoretically and experimentally. Overall, our findings suggest that the acoustic-hydraulic nozzle has significant potential in various technological applications that require high-throughput, fine spray production. Further improvement of the proposed method will concern the optimization of spray conditions for different liquids differing in viscosity, density, and surface tension. Also, the case of the presence of hydrodynamic cavitation along with acoustic cavitation has not yet been studied. This mode can occur when the geometric characteristics of the nozzle are changed in order to increase the performance of the nozzle. In general, further parametric study of the acoustic-hydraulic nozzle may open up new prospects for the use of the proposed method. Figure 11: Volumetric flow rate of liquid \(Q\): calculated curves and experimental points for two values of ultrasound intensity \(I\). **Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app132212330/s1](https://www.mdpi.com/article/10.3390/app132212330/s1)]([https://www.mdpi.com/article/10.3390/app132212330/s1](https://www.mdpi.com/article/10.3390/app132212330/s1)), Figure S1: Statistical characteristics of the particle size distribution for \(p\) = 200 kPa. Figure S2: Statistical characteristics of the particle size distribution for \(p\) = 300 kPa. Figure S3: Statistical characteristics of the particle size distribution for \(p\) = 400 kPa. Figure S4: Statistical characteristics of the particle size distribution for \(p\) = 500 kPa. Figure S5: Statistical characteristics of the particle size distribution for \(p\) = 600 kPa. Figure S6: Statistical characteristics of the particle size distribution for \(p\) = 700 kPa. Figure S7: Statistical characteristics of the particle size distribution for \(p\) = 800 kPa. Figure S8: Statistical characteristics of the particle size distribution for \(p\) = 900 kPa. **Author Contributions:** Conceptualization, A.S. and O.K. ; methodology, D.G. ; investigation, R.D. ; resources, S.T. ; writing--original draft preparation, O.K. ; writing--review and editing, supervision, A.S.; project administration, A.S.; funding acquisition, S.T. All authors have read and agreed to the published version of the manuscript. **Funding:** This study was carried out with a grant from the Russian Science Foundation \(N\) 23-19-00875, [[https://rscf.ru/project/23-19-00875/](https://rscf.ru/project/23-19-00875/)]([https://rscf.ru/project/23-19-00875/](https://rscf.ru/project/23-19-00875/)) (accessed on 29 October 2023). **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable.