DROP SPECTRA FOR PNEUMATIC ATOMIZERS AT LOW DISCHARGE RATES
Drop sizes emitted from nozzles of three pneumatic-atomizing designs were laser-diffraction determined for 65 
and 130 mL/min flow rates of water, Bettakill soybean oil, and Orchex 796, and Sun 7N mineral oils. Air pressures ranged 
from 12 to 66 kPa, with exact air pressure ranges varying among nozzle designs for satisfactory operation. An AirJet nozzle 
produced drops with volume median diameters (Dv0.5) that ranged from 85.9 µm (Orchex 796, 65 mL/min, 53 kPa air 
pressure) to 589.1 µm (water, 130 mL/min, 12 kPa air pressure). AirJet Dv0.5 values > 200 µm occurred in 30% of the runs. 
An AirTec nozzle delivered a Dv0.5 range of 118.4 µm (Orchex 796, 65 mL/min, 53 kPa air pressure) to 535.3 µm (Bettakill, 
130 mL/min, 46 kPa air pressure). AirTec Dv0.5 values > 200 µm occurred in 78% of the runs. A LoAir nozzle emitted drops 
with Dv0.5 values ranging from 103.2 µm (Orchex 796, 65 mL/min, 25 kPa air pressure) to 425.8 µm (Bettakill, 130 mL/min, 
12 kPa air pressure). LoAir Dv0.5 values > 200 µm occurred in 43% of the runs. Small drop production (< 105 µm) was 
inversely, and non-linearly proportional to the Dv0.5. Doubling the liquid flow rate from 65 to 130 mL/min increased the 
mean Dv0.5 for the AirJet, AirTec, and LoAir nozzles by 48, 54, and 24%, and decreased the air flow rate by 8, 18, and 8%, 
respectively. Characteristic relations between Dv0.5 and pneumatic atomization energy were observed for each nozzle design.