Effects of Nozzle Spray Angle on Droplet Size and Velocity

Spray applicators have many choices in selecting a spray nozzle to make an application of an agricultural product. They must balance flow rate, spray pressure, and nozzle type and setup to deliver their agrochemical in the right droplet size for their particular needs. Studies were conducted to determine the spray exit angle and droplet velocity from three different flat fan nozzles (80 degrees, 40 degrees, and 20 degrees) at three different spray pressures (140, 280, and 420 kPa). Each combination of nozzle and pressure was evaluated in a wind tunnel with airspeeds of 35.7, 53.6, 62.6, 71.5, and 80.5 m/s. At the nozzle exit, droplet velocities for the three nozzles tested were approximately 14, 20, and 25 m/s (similar to 30, 45, and 56 mph) for spray pressures of 140, 276, and 415 kPa (20, 40, and 60 psi), respectively. Droplet velocities were constant across the entire flowfield measured with airstreams speed were 35.7 m/s (80 mph), but as the airstream speed increased, droplets at the end of the spray sheet were quickly accelerated. The data presented will allow applicators and researchers to select the nozzle and operating conditions that best suit their spraying needs.