Evaluating the effect of operating pressure, nozzle size and mounting height on droplet characteristics of rotating spray plate sprinkler

The droplet characteristics are imperative for evaluating the hydraulic performance of a sprinkler. The experiments were performed in an indoor laboratory to evaluate the effect of operating pressures (P1-100, P2-150, P3-200 and P4-250 kPa) and sprinkler mounting heights (H1-100 and H2-150 cm) on the droplet characteristics of three nozzle diameters (3.18, 4.76 and 6.35 mm) of Nelson R3000 sprinkler. The spray droplet diameter and velocity were measured using a two-dimensional video disdrometer, and the plastic catch cans were used to measure water application rate in radial direction. Kinetic energy and specific power were calculated using experimental data. It was found that the larger nozzle diameter produced the higher application rate under higher pressure, as the highest application rate for nozzle diameters of 3.18, 4.76 and 6.35 mm were found to be 9.17, 19.35 and 25.37 mm/h respectively under P4, and the volumetric mean droplet diameter and velocity increased by increasing the distance from the sprinkler head. The pressure and height affected the specific power of spray droplets as the peak values of specific power for all selected nozzle sizes were found at P4 and H2 i.e., 0.027, 0.056 and 0.10 W/m² for nozzle diameters of 3.18, 4.76 and 6.35 mm respectively and the specific power was increased by increasing the nozzle diameter. Therefore, it is suggested that the R3000, sprinkler with tested nozzle sizes should be operated between 100 and 200 kPa for its efficient working, to avoid expected runoff and erosion as well.