基于弹道理论有风条件下折射式喷头喷灌均匀度研究

摘要

为计算有风条件下折射式喷头水量分布及喷灌均匀度,以弹道轨迹理论为基础,依据风速分布模型,建立有风条件下折射式单喷头水量分布计算方法,采用该方法模拟出有风条件下Nelson D3000型喷头倒挂安装方式下水量分布特性,通过与实测资料进行对比,验证了模拟具有较高的准确度,可应用于有风条件下折射式喷头水量分布计算.在此基础上,选用4.76 mm(24号)喷嘴直径,模拟出不工况下单喷头水量分布,计算出组合情况下喷灌均匀度,分析了风速、风向、喷头间距、工作压力和安装高度5种因素对喷灌均匀度的影响,并对蒸发漂移损失进行了分析.结果表明:95％的置信区间下,喷头布置间距对喷灌均匀度的影响最显著,其次是安装高度和喷头工作压力,风速和风向对喷灌均匀度影响不显著.风速、喷头工作压力和安装高度都会对蒸发漂移损失产生影响,其中工作压力影响最大.当选用Nelson D3000型喷头在风速小于6 m/s的环境下喷灌时,应将喷头安装间距固定在2.13 ～3.04m范围内.另外,该安装间距范围内,喷头安装高度和喷灌压力增大后,喷灌均匀度增大的效果不明显,因此应采用低压喷灌以降低喷灌系统运行成本;考虑到较高的喷头安装高度会产生较大的蒸发漂移损失,喷灌时还应适当降低喷头安装高度,以提高喷灌水分利用率.%In order to simulate fixed spray-plate sprinkler water distribution and Christiansen uniformity (CU) under open field conditions,the method for calculating water distribution was proposed by applying droplet size distribution,simulation of droplet distribution utilize droplet trajectory computations and wind-distored model.The accuracy of water distributions of Nelson D3000 spray sprinkler was validated by comparing simulated with observed patterns,it was found that the software appeared to be an effective predictor of sprinkler performance in wind.Under this premise,the water distribution was simulated at different wind speeds with 4.76 mm nozzle diameters (24#),the factors,including wind speed,wind direction,sprinkler spacing,working pressure and riser height,which may affect CU,the wind drift and evaporation losses (WDEL) under different working conditions were analyzed.The results showed that sprinkler spacing had the most important influence on CU at 95％ confidence interval,and it was followed by riser height and working pressure,wind speed and wind direction did not significantly affect CU.Increasing wind speed,working pressure or riser height indicated an increase in the OWDEL,and working pressure can dramatically affect the OWDEL on account of smashing large water droplet to pieces.Using this sprinkler,the lateral moving irrigation system can attain a high uniformity coefficient at 2.13 ～3.14 m sprinkler spacing along the lateral when the wind speed was lower than 6 m/s,and with this range of mounting spacing,increasing sprinkler riser height or working pressure cannot promote a higher CU distinctly,low working pressure was recommended considering little cost in the design of the sprinkler irrigation system.In addition,decreasing the riser height can reduce WDEL effectively,in order to increase water use efficiency,low height cooperated with plant height was reasonable.