The function of a nozzle atomizer is the acceleration and break-up of bulk liquid flow, terminating with the dispersion of the resulting droplets to form a spray. Pressure energy is utilized for bulk liquid bulk break-up. A single small diameter hole is not considered an atomizer, although the liquid may be disintegrated if the liquid jet is turbulent enough, because the droplets are not dispersed by the action of the hole itself.
Pressure Nozzle Atomization
The principle of the pressure nozzle is the conversion of pressure energy within the liquid bulk into kinetic energy of thin moving liquid sheets. The sheets break up under the influence of the physical liquid properties and by the frictional effects with the medium into which the liquid sheet is discharged. Invariably the medium is air. Liquid sheets range in thickness from 0.5 to 4 micron. Sheets rapidly become unstable as any influence that causes fluctuations in the order of this thickness promotes disintegration. Conversion of pressure energy is carried out in such a way that the resulting liquid motion is rotary. This arrangement permits greater energy transfer through thin liquid film formation leading to improved atomization. Two designs of internals that create liquid rotation in a pressure nozzle are shown in Figure, which represents a once-through liquid flow design where droplet size and feed rate vary with operating pressure.