Theoretical and experimental study of air blast atomizer

The typical small air blast atomizer with rotating air outside the pressure swirl nozzle was investigated both theoretically and experimentally. The equations describing the flow of a rotating hollow liquid jet in a gaseous environment, where there is a difference between outer and inner pressures in a space which is divided by the liquid film were developed. The effect of surface tension, gravitational forces, and inner-outer pressure difference on the liquid film and its disintegration was considered. The relevant set of equations describing the physics was solved numerically. The initial conditions for the equations: pressure distribution inside and outside of the 'onion' as a function of the outer rotating air and liquid parameters, were obtained experimentally. The numerical results were verified by the experimental study. It was shown that two shapes of liquid film nearby nozzle exit exist - 'onion' and open film. Shape of the liquid film for the given liquid pressure drop depends mainly on air pressure difference outside and inside of the film. The two resulting spray modes were found to have drastically different droplet characteristics. These results can be applied for use in estimating the parameters of the air-blast atomizers that operate with very low liquid pressure drop.