Principles and droplet size distributions of various spraying methods: a review

Abstract

Spraying refers to the process of forming small droplets of a liquid and dispersing them in air or on the surface of an object. Spraying is ubiquitous because it enables a liquid widely and uniformly dispersed. The existing spraying methods can be broadly categorized as ultrasonic, liquid compression, and two-phase nozzle-based. These different methods utilize different principles, with advantages and disadvantages. Thus, it is necessary to understand how different methods are suited to the applications of interest. In particular, the droplet size plays a significant role. Many studies have been conducted to characterize different spraying methods, but little systematic organization and summarization with respect to the droplet size has been done. Herein, we introduce the most widely used spraying methods and explain their spraying principles, fields of use, and appropriate operating environments. We focus on the droplet size aspect. This review is likely to be useful in the design and development of spraying devices.