喷嘴形状对喷洒水滴动能的影响

对特定的土壤来说，喷洒水滴动能是优选喷头型式时需要考虑的重要因素。利用面粉法测得的圆形和方形喷嘴的水滴分布资料，用水滴运动方程确定水滴落地时的速度，计算了单位质量水滴沿径向不同位置处的动能和总动能。在相同压力下，方形喷嘴形成的水滴所具有的动能小于同流量的圆形喷嘴；在满足一定的水滴总动能要求时，方形喷嘴可在比圆形喷嘴低９８ｋＰａ的压力下工作，从而达到节能的目的。通过分析得出了可用于由中数直径估算中压喷头的水滴总动能的回归方程。还研究了竖管高度对水滴总动能的影响。结果表明，在常用的竖管高度范围内，高度每升高１ｍ，圆形喷嘴的水滴总动能增加约５％，方形喷嘴的水滴总动能增加６％～９％。

Effect of Nozzle Shape on the Spraydrop Kinetic Energy from Sprinklers

Information on the drop energy from sprinklers is important for choosing optimum sprinkler type for a particular soil.Droplet size distributions for circular and square nozzles were measured at different pressures using a flour technique.Drop velocities were determined using a trajectory model.Drop kinetic energy per unit of applied water along a radial distance and the overall drop energy were calculated.For a given pressure,a square nozzle produced smaller overall energy than the circular nozzle.For a required overall drop energy,the pressure for a square nozzles can be 98 kPa lower than that for the circualar nozzle.The median droplet diameter was found to be a good predictor of overall kinetic energy,and the relationship between overall energy and median droplet diameter developed in this article can be used to estimate the energy from medium sized sprinklers.Nozzle elevation was found to increase the overall kinetic energy about 5% for per meter of elevation for the circular nozzle and 6%-9% for the square nozzle,at practical sprinkler riser heights.