Effervescent atomization

Abstract

Effervescent atomization is a method of twin-fluid atomization that involves bubbling a small amount of gas into the liquid before it is ejected from the atomizer. The technique of bubbling gas directly into the liquid stream inside the atomizer body is essentially different from other methods of twin-fluid atomization (either internal or external mixing) and leads to significant improvements in performance in terms of smaller drop sizes and/or lower injection pressures. Furthermore, the amount of atomizing gas required is considerably less than what is employed in all other twin-fluid atomization techniques. Effervescent atomization has been used successfully in a number of applications since its inception over ten years ago. It has been well studied during this period, and the published literature includes experimental and analytical investigations of both atomizer performance and the fundamental mechanisms involved in the atomization process. The literature also includes application-oriented studies that report the development of effervescent atomizers for gas turbine combustors, consumer products, furnaces and boilers, internal combustion (IC) engines, and incinerators. Through these studies a fair appreciation of the capabilities of the technique has been achieved. Continuing work is aimed at exploring the use of effervescent atomization in new areas, as well as acquiring a better understanding of current applications. More in-depth studies are also in progress on the various basic mechanisms that contribute to the overall atomization process. The purpose of this article is threefold. First, to summarize the results obtained from investigations of effervescent atomizer performance embracing wide variations in atomizer design, liquid properties, and operating conditions. Second, to review current theories on the basic mechanisms involved in the atomization process and to discuss the scope for future research. Third, to provide an overview of current applications and to suggest possible areas for future practical applications, including fire suppression, paint sprays, agricultural sprays, and fuel injection for liquid-rockets and spark-ignition IC engines.