NOZZLE DISCHARGE COEFFICIENT FOR CENTER-PIVOT SYSTEM

This study aimed to determine the discharge coefficients (C-d) of sprinkler fixed-nozzles (Senninger, Nelson and Fabrimar), used in Brazilian center-pivot equipment, under laboratory conditions. These tests used the pressure range standard existing in the nozzle market (psi). A set of 45 Senninger, 42 Nelson and 36 Fabrimar nozzles were assessed, with three replications, in a total of 369 tested nozzles. Operating pressures ranged from 6 to 30 psi (41.37 to 206.84 kPa), with a reading gap of 2 psi (13.79 kPa), totaling 13 measures for nozzle. Discharge coefficient curves were drawn as function of nozzle size and operating pressures, which were 10, 15, 20, and 30 psi (68.95, 103.42, 137.90 and 206.84 kPa). Two precision pressure gauges (one analog and one digital) were used; being calibrated against a dead weight gauge. Flow rates were obtained using three electromagnetic induction gauges calibrated with volumetric data. Nozzle diameters were measured using a profile projector Model HB 400 (Starrett, Sao Paulo, Brazil). The results evidenced that discharge coefficient varies with nozzle diameter and operating pressure. Tests showed C-ds within the range of 0.88 to 0.98, for the assessed nozzles.