DROP SPECTRA FOR PNEUMATIC ATOMIZERS AT LOW DISCHARGE RATES

Drop sizes emitted from nozzles of three pneumatic-atomizing designs w ere laser-diffraction determined for 65 and 130 mL/min flow rates of w ater; Bettakill soybean oil, and Orchex 796 and Sun 7N mineral oils. A ir pressures ranged from 12 to 66 kPa, with exact air pressure ranges varying among nozzle designs for satisfactory operation. An AirJet noz zle produced drops with volume median diameters (D-v0.5) that ranged f rom 85.9 mu m (Orchex 796 65 mL/min, 53 kPa air pressure) to 589.1 mu m (water; 130 mL/min, 12 kPa air pressure). AirJet D-v0.5 values > 200 mu m occurred in 30% of the runs. An AirTec nozzle delivered a D-v0.5 range of 118.4 mu m (Orchex 796 65 mL/min, 53 kPa air pressure) to 53 5.3 mu m (Bettakill, 130 mL/min, 46 kPa air pressure). AirTec Dv0.5 Va lues > 200 mu m occurred in 78% of the runs. A LoAir nozzle emitted dr ops with D-v0.5 values ranging from 103.2 mu m (Orchex 796 65 mL/min, 25 kPa air pressure) to 425.8 mu m (Bettakill, 130 mL/min, 12 kPa air pressure). LoAir D-v0.5 values > 200 mu m occurred in 43% of the runs. Small drop production (< 105 mu m) was inversely, and non-linearly pr oportional to the D-v0.5. Doubling the liquid flow rare from 65 to 130 mL/min increased the mean D-v0.5 for the AirJet, AirTec, and LoAir no zzles by 48, 54, and 24%, and decreased the airflow rate by 8, 18, and 8%, respectively Characteristic relations between D-v0.5 and pneumati c atomization energy were observed for each nozzle design.