Experimental Study on Droplet Characteristics of Rotating Sprinklers with Circular Nozzles and Diffuser

Abstract

The characteristics of spray droplets are important for calculating the hydraulic performance of sprinklers. In order to evaluate the effects of working pressure and nozzle diameter on the near ground droplet characteristics of the Nelson R33 sprinkler, an experiment was conducted to test the droplet size and velocity by using a two-dimensional video disdrometer (2DVD). Based on the water application rate, droplet diameter and velocity, the kinetic energy was calculated. The results show that there is an exponential positive correlation between the range and the volume-weighted mean particle size of droplets (VMD). The average kinetic energy of a single droplet fits well with the power function model. Under the minimum pressure of 200 kPa, the diameter and kinetic energy of droplets are large, and the peak values are 5.67 mm and 0.0092 J, which are 1.14 to 1.62 times and 1.18 to 5.68 times those of other working conditions, respectively. When the nozzle diameter is the smallest (4.4 mm), the droplet diameter and peak kinetic energy are 1.12 to 1.58 times and 1.02 to 1.26 times higher than 4.8 and 5.2 mm. Therefore, it is not recommended to work under the condition of less than 250 kPa, and a small-diameter nozzle should be selected while ensuring uniform kinetic energy.