Abstract:

Theoretical explanations on spray characteristics having positive pressure index were presented. Experimentally using high pressure container for drop size measurement will cause recirculation of small droplets introducing spray measurement error. Theoretically, two factors are of importance. For air blast atomizer the interaction between turbulent fluctuation and droplet cluster causing droplet collision between droplets of different sizes promotes droplet agglomeration. For pressure swirl atomizer, because of the fast decay of the filament velocity after leaving the nozzle exit under high back pressure, it is possible that the aerodynamic forces encounted by the filament under high back pressure, which determine the final formation of spray, may even be less than that under low back pressure. A detailed analysis was provided which showed clearly that a very popular statement in atornization literature that the aerodynamic force for atornization will increase with pressure, is not always true.

Key words: Nozzle, Spray characteristics, Drop size