基于2DVD的非旋转折射式喷头水滴直径分布规律

采用基于三维视频粒子测量原理的视频雨滴谱仪(Two-dimensional video disdrometer,2DVD)对喷灌机中常用的Nelson D3000型喷头在多个工作压力下水滴直径沿射程的分布进行了测量,分析了水滴直径沿射程的变化趋势及水滴速度、水滴角度与水滴直径之间的关系。结果表明:水滴直径与射程符合指数函数关系,在距离喷头相同测点处,水滴直径随工作压力的升高而减小,而射程末端的水滴直径随着压力的升高而增大;水滴速度随水滴直径增加而增大,两者呈对数关系;水滴落地时与地面夹角(简称水滴角度)随水滴直径增加呈减小趋势,水滴直径小于1.0 mm时,50、100、150和200 kPa工作压力下,与地面夹角为90°的水滴个数占总水滴数的比值分别为90.46%、84.46%、89.91%和89.15%,其余水滴与地面夹角在30°~89°之间,水滴直径在1.0~2.25 mm范围内,水滴角度随水滴直径的增加迅速减小,水滴直径大于2.25 mm时减小趋势变缓,4个工作压力下最大直径水滴落地时与地面夹角平均值为45°;工作压力对于水滴直径与速度、水滴直径与角度之间的关系影响较小。

Drop Size Distribution of Fixed Spray-plate Sprinklers with Two-dimensional Video Disdrometer

A two-dimensional video disdrometer (2DVD) was used to measure drop size, drop velocity and drop angle from Nelson D3000 spray-plate sprinklers with a 4.78mm nozzle and operating pressure of 50, 100,150, 200kPa. The relationship among drop sizes, drop velocity and drop angle were analyzed. Results indicated that the relationship between drop diameter and distances along the sprinkler met exponential function. The volumetric mean diameter increased with the distance along the sprinkler increased, and at the same location from the sprinkler the average droplet diameter decreased with the increase of working pressure. The relationship between drop velocity and drop diameter met logarithmic function. Drop velocity increased with the drop diameter increased, and the effect of operating pressure on the relationship between drop diameter and velocity was not obvious. Drop angle decreased with the increase of drop diameter. When drop diameter was smaller than 1.0mm and operating pressure was at 50, 100, 150, 200kPa, 90.46%, 84.46%, 89.91% and 89.15% of the droplets descended perpendicularly to the ground, respectively. The rest of the droplets descended to the ground with angle between 30°~89°. When drop diameter was between 1.0mm and 2.25mm, the drop angle decreased rapidly with the drop diameter increased. And when drop diameter was greater than 2.25mm, the decrease trend became slower. The relationship between drop angle and drop diameter met a good linear function, and the effect of operating pressure on the relationship between drop angle and diameter was not obvious.