Spray characteristics and factors affecting spray angle of polyacetal (POM) nozzle discs

The aim of this study was to determine the effect on spray characteristics, discharge coefficient and spray angle of the orifice diameter, cores and spray pressure variables in hollow cone disc-core type spray nozzles. In the trials, nozzle discs of 1.0 mm, 1.2 mm, 1.6 mm, 2.0 mm and 2.4 mm orifice diameters; cores with blue colored (2-slot), brown colored (3-slot), yellow colored (2-slot) and stainless steel (2-slot) were used. In the application, spray pressures were 2, 4, 6, 8 and 12 bars. The highest flow rate was obtained with blue core, while the lowest flow rate was provided with stainless steel. The spray angle was significantly affected by orifice diameter, core and spray pressure variables. While the spray angle of the nozzles with low flow rate increased at constant pressure and the same orifice diameter, the spray angle decreased with high flow rate. The highest spray angle was determined with blue core and, the spray angle of the stainless steel core was found to be the lowest. According to the curve estimation method, the polynomial functions with high R2 between spray angle and pressure in the combination of nozzle orifices and core groups were obtained. At constant spray pressure of 3 bars, the nominal spray angles of the nozzle discs with 1.0 mm, 1.2 mm, 1.6 mm, 2.0 mm and 2.4 mm orifice diameters varied between 49°-60°, 60°-72°, 74°-85°, 80°-97° and 89°-101°, respectively. The spray angle varied in a stabile range above a certain spray pressure. The lowest spray pressure, spray angle of which varied in a stabile range was 6 bars for the nozzle disc of 1.0 mm diameter, 4 bars for the nozzle discs of 1.2 mm and 1.6 mm diameters, and 2 bars for the nozzle discs of 2.0 mm and 2.4 mm diameters. The mean discharge coefficient was determined as 0.411, 0.362, 0.285, 0.236 and 0.201 for the nozzle discs of 1.0 mm, 1.2 mm, 1.6 mm, 2.0 mm and 2.4 mm diameters, respectively. This result showed that the nozzle orifice diameter increased, and caused that the droplet velocity at the orifice exit decreased. The droplet velocity varied between 3.63-22.13 m s-1 in the combination of nozzle orifice and core groups, and as the spray pressure increased, droplet velocity increased. The droplet diameter of the hollow cone spray nozzles in the range of 2-12 bars spray pressures was ranged between 76.3-219.0 µm, and produced mostly very fine droplets and relatively fine and medium droplets. Increasing the spray pressure was not found efficient on kinetic energy of droplet at orifice exit of nozzle. But, as the nozzle orifice diameter increased the kinetic energy of droplet decreased. While the terminal velocity of droplet decreased as the spray pressure increased, increasing the nozzle orifice diameter caused the terminal velocity of droplet increased. In the spray pressure of 2 bars, stopping distance of droplet increased. The drift potential mean was found in the range of %8.5-%13.5 for spray pressure of 2 bars, and %15.3-%19.9 for spray pressure of 12 bars. In reference to the results of the correlation analysis between the variables describing the spray characteristics in hollow cone spray nozzles, the relation between variables which was significant was shown with regression equations.