Influence of the trajectory angle and nozzle height from the ground on water distribution radial curve of a sprinkler

Abstract

In order to evaluate the effects of the variation of two factors of the working condition, the trajectory angle and the nozzle height from the ground, on the water distribution radial curve of a sprinkler, a mathematical model, able to elaborate with a very good accuracy the size spectrum of droplets generated by a nozzle starting from experimental water distribution radial curves, was used and applied in reversed form. In a previous paper, 37 dimensional droplet spectra were obtained, generated by four sprinklers under varying conditions of operating pressure and nozzle size, but with a single value of trajectory angle and a single value of the nozzle height from the ground level. The application of the mathematical model to the 37 dimensional spectra of the droplets has led to new water distribution radial curves on varying the trajectory angle and the nozzle height. The evaluation of these curves, along with original and experimental ones, has been made using the uniformity of distribution, by means of Christiansen's coefficient CU. Increasing values of pressure and nozzle size provide the best CU. This is applied to all heights of the nozzle from the ground and to almost all trajectory angle values. In all cases, different nozzle heights do not show significant differences in CU values. This also occurred in the comparison of three different trajectory angles, unless the larger diameter and lower height of the nozzle where the CU coefficient gets worse with decreasing the trajectory. The evaluation of the new water distribution radial curves was also made in relation to the produced radius of throw R (m), and it was found that R is positively influenced by all the variables involved. Considering this relationship, two monomial type equations (one for nozzle discharge up to 120 dm3/min and radius of throw less than 30 m and one for nozzle discharge above 120 dm3/min and higher throw radii) were found that can predict R compared to the discharge of the nozzle, the operating pressure, the trajectory angle, and the height of the nozzle from the ground level. The comparison between the calculated and actual values of R shows a relative error, for all sprinklers and all operating conditions, respectively equal to 6.9% in the first case and 4.1% in the second case.

Keywords

• sprinkler, nozzle, trajectory angle, distribution uniformity, nozzle height.