AIr Core in Pressure Swirl Atomizing Nozzles

Extensive research in pressure-swirl nozzles has been made by several researchers for the last few decades because of the inherent impact of swirl nozzles on widespread and diversified fields of both power and process industries. Design of nozzles for specific applications requires an understanding of the hydrodynamics of nozzle flow. The formation of a central air core in pressure nozzles with tangential entry is a direct consequence of nozzle hydrodynamics and plays the key role in determining the thickness and velocity of the liquid sheet at the discharge orifice. Though a large number of works pertaining to flow in swirl nozzles have been carried out by several investigators, relatively less attention has been paid to predict the shape and size of the air core in swirl nozzles. The present paper makes a comprehensive and critical review of the studies on air-core diameter in pressure nozzles with tangential entry. The focus of the review is the integration of available information in the literature in light of a conceptual understanding of the aspects such as (i) formation of the air core in swirl nozzles and (ii) the shape and size of a fully developed air core along with its dependence on nozzle flow and nozzle geometry. Such an understanding is essential in predicting performance characteristics of nozzles under different operating situations.