Near field spray measurements for fixed spray plate sprinklers

Abstract

The spatially resolved spray scanning system (4S) is a new technology providing high-fidelity near-field spray characteristics generated by sprinklers, capturing all the physical parameters necessary to completely describe the sprinkler’s spray. In this study, a fixed spray plate sprinkler (FSPS) using three different deflector plates and two orifice sizes has been successfully characterized using the 4S. The current research demonstrates the potential of 4S technology to support irrigation sprinkler design optimization. The influence of the deflector plate design on spray characteristics can be clearly observed in the 4S measurements. It has been shown that deflector plate design (smooth, grooved, flat or two-level) generates deep changes in the important near-field spray properties. The baseline smooth-flat deflector plate generates a homogenous spray mainly concentrated at a polar angle of 90°. While the grooved-flat deflector plate presents a fluctuating spatial distribution, with similar volume flux and reference velocity, and larger drop sizes (~ 15%) as compared with baseline, two-stage deflector plates tend to redirect the main water flow from a polar angle of 90° to 110°, doubling the volume flux and resulting in an important increase in drop size (> 20%) and reference velocities (~ 7%) as compared with the baseline. In addition, measurements show frame arms induce local decreases in volume flux and drop velocity by as much as 60% compared to average values. While the ability of the 4S to provide high-fidelity near-spray descriptions of FSPS has been demonstrated, application to other sprinklers types such as impact, spinners and off-center wobbling could be limited and will be explored in future research.