ATOMIZATION CHARACTERISTICS OF HIGH–FLOW VARIABLE–ORIFICE FLOODING NOZZLES

Droplet spectra factors for variable–orifice flooding nozzles in quasi–static air were investigated to possibly aid the reduction of spray drift, and to provide a basis for future atomizer design. A laser–diffraction instrument measured the droplet size spectra of water sprays through orifices with diameters ranging from 1.14 to 6.35 mm. Spray discharge flow rates up to 40 L min –1 were measured with a Coriolis–type sensor. Nozzles produced an array of droplet size spectra with volume median diameters (Dv0.5) ranging from 296 to 1062 m. For single–orifice flooding nozzles, orifice diameter was the most important factor positively correlated with droplet size spectra factors, except the Dv0.9. For flooding nozzles utilizing two orifices in series, the magnitude of difference between the two orifice diameters was the most important factor positively correlated with droplet size spectra factors. In addition, two–orifice flooding nozzles had strong negative correlations between pressure and droplet size factors, whereas single–orifice flooding nozzles had strong positive correlations between flow rate and droplet size factors. A unique flow—pressure phenomenon, in which flow decreased or remained steady with increasing pressure, was observed for some orifices and pressures, possibly due to orifice inlet limiting conditions. The use of regression coefficients predicted most droplet size spectra factors with coefficients of determination (r 2 ) ranging from 0.72 to 0.91, except for low r 2 values (0.11 to 0.50) associated with the Dv0.9 of single–orifice nozzles.