# Innovative Acoustic-Hydraulic Method for High-Performance Fine Liquid Atomization
## 1 Introduction  
Liquid atomization is a crucial manufacturing process that finds application in a diverse range of fields. Over time, numerous spraying methods and devices have been developed based on different physical principles, including hydraulic, pneumatic, and mechanical, and their combinations [1]. The hydraulic atomization of liquid is the most conventional method, wherein the liquid is converted into droplets when it flows through the nozzle hole under high pressure. This process is extensively employed in industries and agriculture for the application of various solutions, chemicals, fertilizers, etc. [2]. Hydraulic atomization allows for high atomization performance at high pressures (up to 1000 mL/s), but the droplet size is 100-500 \(\upmu\)m or more. Combined types of nozzles include, for example, impingement-type nozzles [3], impinging jet nozzles [4], impact-type pneumatic nozzles [5], centrifugal-pneumatic type nozzles [6], and others. This variety of spraying methods is caused by the requirements of specific technological applications: in some cases, high dispersion and a narrow droplet size distribution are required; in others, certain spray geometry is required; in others, a stable spray speed, etc. There are a number of tasks that require both high droplet dispersion and high productivityof spray creation. Simultaneous fulfillment of such requirements is difficult to achieve. The novelty of this work lies in the development of a new method of liquid spraying, combining high dispersion and high productivity. Simultaneously high aerosol production and high droplet dispersion are required in technological processes such as aerosol drying, aerosol coating, aerosol surface treatment, and aerosol drug delivery. In aerosol drying, for example, the material is subjected to spraying to create an aerosol, which then quickly dries, forming fine dispersed particles with high surface activity [7]. In aerosol coating, high droplet dispersion allows for uniform coating application on the surface, and high aerosol production ensures efficient coverage of large areas [8]. In aerosol surface treatment, high droplet dispersion helps to evenly distribute the treating substance, and high aerosol production accelerates the treatment process [9]. In aerosol drug delivery, high droplet dispersion is necessary to ensure rapid and uniform penetration of the drug into the body, and high aerosol production allows for the delivery of the required amount of medication in a short period of time [10]. One innovative spraying method is ultrasonic spraying, which uses ultrasonic vibrations to create fine droplets of liquid. Ultrasonic liquid atomization is widely used in various applications (medical inhalers, reactors, dryers, powder atomization, etc. [11; 12]). The advantage of this method is the stable and predictable relationship between operating parameters, spraying speed, and droplet diameter [13; 14]. Additionally, ultrasonic spraying results in the narrowest droplet size distribution compared to other spraying methods. However, the downside of using ultrasonic spraying is low productivity, and the higher the droplet dispersion, the lower the productivity of droplet creation [15]. For example, when generating droplets with a diameter of up to 10 \(\upmu\)m, productivity can be as low as 0.1 mL/(s-cm\({}^{2}\)). On the other hand, hydraulic spraying makes it possible to obtain an aerosol with high productivity (tens of mL/s). However, with this spraying method, the droplet dispersion is low, and the higher the productivity, the lower the droplet dispersion (for example, 1000 microns at 25 L/min). Although many combined spraying methods have been created [1], no attempts have been made to combine ultrasonic and hydraulic spraying. This may be due to the complexity of organizing such spraying and the physical processes accompanying it.