Different nozzle structures can result in significantly different atomization performances. Some nozzle types simply cannot achieve the required atomization performance regardless of parameter adjustments. When selecting a nozzle type, it's crucial to consider not only its achievable atomization performance but also its structure, manufacturing difficulty, and applicable range. Representative liquid atomization methods widely used in production and daily life include the following:
Pressure-type: This method converts pressure into fluid kinetic energy to form a high-speed liquid jet or liquid film jet. Upon encountering the surrounding low-speed gas medium, the liquid jet or film breaks under the action of breaking and counter-breaking forces, ultimately achieving atomization. This mainly includes direct-flow nozzles and single-type centrifugal nozzles.
Direct-flow nozzles: Under the action of pressure difference, the spray liquid is ejected through the nozzle and atomized under the action of fluid dynamics and surface tension. The nozzle diameter of a direct-flow nozzle is generally 2–4 mm. A diameter that is too small easily leads to clogging, while a diameter that is too large results in poor atomization. Its spray cone angle is generally between 5° and 15°. The droplets are mainly distributed within a narrow range near the nozzle axis.
Single Centrifugal Nozzle There are two typical types of centrifugal nozzles. One type has a tangential inlet; the liquid enters the centrifugal chamber through a tangential hole in the nozzle housing and is then ejected from the orifice. The other type has a vortex generator; the liquid enters a spiral groove, rotating and moving downwards in a spiral motion. After leaving the nozzle, the liquid particles are no longer constrained by the inner wall and thus move along the axis and tangentially, forming a conical film, the so-called spray cone. The spray cone angle is generally 60°–120°.
**Pneumatic Type** Also known as a media type, the pneumatic type uses air or steam as the atomizing medium to atomize the sprayed liquid. It is generally a two-fluid spray type, with both high-pressure and low-pressure versions. The working principle is to use the kinetic energy of the flowing gas to disperse the liquid column or film, breaking it into droplets.
Rotary Type Also known as a rotating cup type, the rotary type injects liquid into the surface of a high-speed rotating cup or disc. The centrifugal force generated by the high-speed rotation of the cup evenly throws the liquid out, breaking the liquid film and completing the atomization process. Its main advantages are its low price and simple structure.
