喷头安装高度对圆形喷灌机灌水质量的影响

根据作物高度适时调整喷头安装高度,是保证圆形喷灌机灌水均匀度和喷灌效率的重要措施之一。该研究通过引入自主研发的喷头安装高度调节装置,以安装D3000低压折射式非旋转喷头的圆形喷灌机为研究对象,研究了不同喷灌机出流量(8.8、16.7、24.2 m3/h)情况下喷灌机水力性能的稳定性,测试了喷灌机3种出流量在喷头安装高度(0.5、1.0、1.5、2.0、2.6 m)改变时的灌水均匀系数和灌水深度。结果表明,在喷头标准安装高度(1.5 m)下,圆形喷灌机水力性能稳定,喷灌机3种出流量的灌水深度沿径向均呈锯齿形波动,灌水均匀系数为82.5%~84.0%。喷头安装高度小于标准高度时,灌水深度沿径向的分布出现了较大波动,0.5 m时波动最剧烈,灌水均匀系数最大降低23.9%。喷头安装高度大于标准高度时,灌水深度沿径向的分布更为均匀,灌水均匀系数与标准高度的均匀系数无显著差异。与标准高度时的灌水深度测量值相比,喷头安装高度调节后的测量水深相对误差在10%以内。为保证喷灌均匀性和灌水深度,建议作物高度大于1.5 m时,可根据作物高度适时升高喷头安装高度。

Influence of sprinkler height on irrigation performance of center pivot irrigator

Abstract: In most nozzle configuration software, the irrigation uniformity of center pivot irrigation system is simulated from the water distribution characteristics of single sprinkler at a special height. Influenced by the plant height and topographic slope, the actual installation height of sprinkler is often not equal to the simulated height and is kept constant during the growing season of crop as lack of the regulation apparatus, which resulted in the unknown irrigation uniformity and irrigation depth. To guarantee the irrigation uniformity and irrigation efficiency of center pivot irrigation system, the principle of keeping the sprinklers on the top of the plant height was proposed and a control apparatus was invented by changing the insert length of counterweight steel tube into the sag pipe to adjust the sprinkler height timely. In this study, the performance of the center pivot sprinkler system outfitted with D3000 non rotating nozzles spaced at 2.92 m was tested to verify the stability of irrigation uniformity and irrigation water depth at 5 installation heights of sprinkler (0.5, 1.0, 1.5, 2.0, and 2.6 m) and 3 outflow rates of sprinkler machine (8.8, 16.7, and 24.2 m3/h). The height of 1.5 m is the standard value simulated by nozzle configuration software. The outflow rates were obtained by using different sprinkler configuration. Catch cans were arranged in transect to obtain the irrigation water depth along the pivot lateral. The modified Heermann-Hein uniformity coefficient was calculated to evaluate the irrigation uniformity. During each test, the wind speed was smaller than 2 m/s. The results indicated that when the sprinkler was adjusted to the standard height of 1.5 m, the application performance of center pivot irrigation system was basically stable under the 3 outflow rates of sprinkler machine. The irrigation depth changed with zigzag wave along radial direction, and a target irrigation water depth could be obtained accurately through setting a specific rotation speed of the pivot. The modified Heermann-Hein uniformity coefficient along the pivot lateral ranged from 82.5% to 84.0%. When the sprinkler height was smaller than 1.5 m, the irrigation depth changed greatly along radial direction, especially at 0.5 m height, under which the modified Heermann-Hein uniformity coefficient significantly decreased by 23.9%. When the sprinkler height was greater than 1.5 m, the distribution of water irrigated along radial direction was more uniform, and there was no significant difference in uniformity coefficients among the 1.5, 2.0, and 2.6 m installation heights. After the sprinkler height was adjusted, although the irrigation water depth was obviously decreased at the height of 2.6 m because of the greater evaporation resulting from longer flying time, the mean absolute value of relative error for measured water depth was less than 10% compared with that at standard sprinkler height. The experimental results demonstrate that the sprinkler height can be raised timely when the plant height is bigger than 1.5 m to guarantee the uniformity coefficient and irrigation water depth of center pivot irrigation system.