Abstract
Spray sprinklers enable to operate at low pressures (<103 kPa) in self-propelled irrigation machines. A number of experiments were performed to characterize the water distribution pattern of an isolated rotator spray plate sprinkler operating at very low pressure under different experimental conditions. The experiments were performed under two pressures (69 kPa and 103 kPa) and in calm and windy conditions. The energy losses due to the impact of the out-going jet with the sprinkler plate were measured using an optical technique. The adequacy to reproduce the measured water distribution pattern under calm conditions of two drop size distribution models was evaluated. A ballistic model was used to simulate the water distribution pattern under wind conditions evaluating three different drag models: (1) considering solid spherical drops; (2) a conventional model based on wind velocity and direction distortion pattern, and (3) a new drag coefficient model independent of wind speed. The energy losses measured with the optical method range from 20% to 60% from higher to lower nozzle sizes, respectively, for both evaluated working pressures analyzing over 16,500 droplets. For the drop size distribution selected, Weibull accurately reproduced the water application with a maximum root mean square error (RMSE) of 19%. Up to 28% of the RMSE could be decreased using the wind-independent drag coefficient model with respect to the conventional model; the difference with respect to the spherical model was 4%.
Highlights
Self-propelled sprinkler irrigation systems and lateral move and center pivot systems have become an alternative for irrigation modernization, for large scale land holding [1,2,3]
The experimental experimentalcharacterization characterization a low-pressure spray plate was sprinkler was covering a wide range of meteorological conditions, nozzle sizes, and working pressures
The reported technicalthe data of the sprinkler under low windlow conditions could be useful foruseful designing center pivot irrigations systems
Summary
Self-propelled sprinkler irrigation systems and lateral move and center pivot systems have become an alternative for irrigation modernization, for large scale land holding [1,2,3]. According to the last update of the census of agriculture in Spain, the irrigated land with self-propelled systems has increased by approximately 7% over the last five years [4]. At the end of the twentieth century, fixed spray plate sprinklers (FSPS) and rotating spray plate sprinklers (RSPS) contributed to an important improvement on irrigation performance and a reduction of pressure requirements [3,6] compared with the previous impact sprinklers that equipped the irrigation machines. FSPS and RSPS are the most common sprinklers used in self-propelled irrigation machines. In Spain, the escalating electricity cost and consumption in the last ten years [7,8]
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