The droplet velocity and diameter significantly affect both the spatial drift loss and the interfacial deposition behaviors, thus determining the ultimate utilization efficiency during pesticide spraying.Investigating...The droplet velocity and diameter significantly affect both the spatial drift loss and the interfacial deposition behaviors, thus determining the ultimate utilization efficiency during pesticide spraying.Investigating the spatial velocity and diameter evolutions can reveal the mechanism of drift loss and guide to design regulation strategy. Here, we explored the spatial velocity distribution of droplets after leaving the nozzle by particle image velocimetry technology and particle tracking model, considering that the effect of nozzle configuration and the air velocity. It shows that all droplets decelerate rapidly with the velocity attenuation ratio ranging from 50% to 80% within the region of 200 mm below the nozzle.The spatial velocity evolution differences between droplets in crossflow are determined by the competition of vertical drag force and net gravity, and the drag force sharply increases as the droplet diameter decreases, especially for that smaller than 150 μm. Based on the spatial evolution differences of the droplet velocity and diameter, a functional adjuvant was added to the liquid for improving the diameter distribution. And the drift loss was significantly reduced due to the reduction of the proportion of easily drifting droplets.展开更多
上喷式喷头喷洒的水滴粒径可达到毫米级别,且存在非球形的水滴,通常超出了基于光学衍射原理仪器的适用范围。为获取上喷式喷头水滴粒径数据,该文设计1种测试平台,基于摄影法,使用Canon EOS 7D Mark II相机进行照片采集,根据光学传播原...上喷式喷头喷洒的水滴粒径可达到毫米级别,且存在非球形的水滴,通常超出了基于光学衍射原理仪器的适用范围。为获取上喷式喷头水滴粒径数据,该文设计1种测试平台,基于摄影法,使用Canon EOS 7D Mark II相机进行照片采集,根据光学传播原理完成现实物体尺寸与照片像素之间的定标;应用Image Pro Plus软件进行照片处理,分析水滴粒径数据。对上喷式喷淋系统水滴粒径现场测试和数据分析,结果表明Canon EOS 7D Mark II相机能够对0.20 mm级别的物体进行准确成像,相对误差为4%;相机可以捕捉到运动的水滴并且清晰成像;Image Pro Plus软件可通过自适应灰度阈值和亚像素边缘检测算法分割脱焦的水滴成像,通过形态学参数的定量表征分割重叠、拖影的水滴成像;最终得到水滴粒径的概率密度数目分布和累计数目分布。该研究展现了基于摄影法进行上喷式喷头水滴粒径测量的新应用。展开更多
基金This work was financially supported by the National Key Research and Development Program of China(2017YFD0200304).
文摘The droplet velocity and diameter significantly affect both the spatial drift loss and the interfacial deposition behaviors, thus determining the ultimate utilization efficiency during pesticide spraying.Investigating the spatial velocity and diameter evolutions can reveal the mechanism of drift loss and guide to design regulation strategy. Here, we explored the spatial velocity distribution of droplets after leaving the nozzle by particle image velocimetry technology and particle tracking model, considering that the effect of nozzle configuration and the air velocity. It shows that all droplets decelerate rapidly with the velocity attenuation ratio ranging from 50% to 80% within the region of 200 mm below the nozzle.The spatial velocity evolution differences between droplets in crossflow are determined by the competition of vertical drag force and net gravity, and the drag force sharply increases as the droplet diameter decreases, especially for that smaller than 150 μm. Based on the spatial evolution differences of the droplet velocity and diameter, a functional adjuvant was added to the liquid for improving the diameter distribution. And the drift loss was significantly reduced due to the reduction of the proportion of easily drifting droplets.
文摘利用PIV技术对气液两相流场与电场耦合作用下的外混式双流体雾化器荷电喷雾流场特性进行了测量研究,设计了一种带环形气幕的荷电感应装置,以控制喷雾射流在感应荷电过程中出现的液滴卷吸.结果表明:当水流量Q由20 L·h-1增加到36 L·h-1时,射流核心区速度增大,喷雾结构逐渐呈现非对称性,随着流量的增大非对称性越明显;扇形压力pR、雾化压力pB对喷雾流场的对称性及喷雾锥角的变化起重要作用;高压静电作用使得喷雾锥角略微增大,上卷吸现象明显并出现涡旋结构,长时间工作时电极环易积液;电极环气幕压力为100 k Pa时,其低压气流可以有效弱化细小液滴的上卷吸运动,解决电极环积液问题,荷电双流体雾化器运行稳定.
文摘上喷式喷头喷洒的水滴粒径可达到毫米级别,且存在非球形的水滴,通常超出了基于光学衍射原理仪器的适用范围。为获取上喷式喷头水滴粒径数据,该文设计1种测试平台,基于摄影法,使用Canon EOS 7D Mark II相机进行照片采集,根据光学传播原理完成现实物体尺寸与照片像素之间的定标;应用Image Pro Plus软件进行照片处理,分析水滴粒径数据。对上喷式喷淋系统水滴粒径现场测试和数据分析,结果表明Canon EOS 7D Mark II相机能够对0.20 mm级别的物体进行准确成像,相对误差为4%;相机可以捕捉到运动的水滴并且清晰成像;Image Pro Plus软件可通过自适应灰度阈值和亚像素边缘检测算法分割脱焦的水滴成像,通过形态学参数的定量表征分割重叠、拖影的水滴成像;最终得到水滴粒径的概率密度数目分布和累计数目分布。该研究展现了基于摄影法进行上喷式喷头水滴粒径测量的新应用。
