The movement and deposition of the droplets sprayed by agricultural unmanned aerial vehicle(UAV)are influenced by the complex downwash flow field of the rotors.Instead of conducting field experiment,a high speed parti...The movement and deposition of the droplets sprayed by agricultural unmanned aerial vehicle(UAV)are influenced by the complex downwash flow field of the rotors.Instead of conducting field experiment,a high speed particle image velocimetry(PIV)method was used to measure the movement and deposition of the droplets at different rotating speeds of rotors(1000-3000 r/min)or at different transverse injecting points(20-50 cm away from its nearby rotors)in the downwash flow field of an agricultural UAV with eight rotors and conical nozzles.The maximum speed and size of the high speed zone of the droplets were found greatly influenced by the downwash velocity.The initial spray angle of the nozzle declined with the increase of downwash flow speed.It was found that the downwash velocity could not only change the deposition zone of the droplets,but also influence their distribution.The increase of the downwash velocity would increase the deposition uniformity of the droplets.The nozzle position in the downwash flow field could also influence the deposition of the droplets.When the transverse distance between the nozzle and its nearby rotors increased,the relative deposition near the downwash flow of the rotors increased simultaneously.However,the distance between the deposition peak and the nozzle stayed constant.The initial spray angle of the nozzle was not influenced by the transverse distance between the nozzle and its nearby rotors.The research results could provide a theoretical basis and reference for the optimization of the spray application of multi-rotor UAV to minimize droplets deposition uncertainty.展开更多
基金the National Natural Science Foundation of China(31601228)the Youth Science Fund of the Beijing Natural Science Foundation(6164032)the Youth Science Fund of Beijing Academy of Agriculture and Forestry Sciences(QNJJ201631)。
文摘The movement and deposition of the droplets sprayed by agricultural unmanned aerial vehicle(UAV)are influenced by the complex downwash flow field of the rotors.Instead of conducting field experiment,a high speed particle image velocimetry(PIV)method was used to measure the movement and deposition of the droplets at different rotating speeds of rotors(1000-3000 r/min)or at different transverse injecting points(20-50 cm away from its nearby rotors)in the downwash flow field of an agricultural UAV with eight rotors and conical nozzles.The maximum speed and size of the high speed zone of the droplets were found greatly influenced by the downwash velocity.The initial spray angle of the nozzle declined with the increase of downwash flow speed.It was found that the downwash velocity could not only change the deposition zone of the droplets,but also influence their distribution.The increase of the downwash velocity would increase the deposition uniformity of the droplets.The nozzle position in the downwash flow field could also influence the deposition of the droplets.When the transverse distance between the nozzle and its nearby rotors increased,the relative deposition near the downwash flow of the rotors increased simultaneously.However,the distance between the deposition peak and the nozzle stayed constant.The initial spray angle of the nozzle was not influenced by the transverse distance between the nozzle and its nearby rotors.The research results could provide a theoretical basis and reference for the optimization of the spray application of multi-rotor UAV to minimize droplets deposition uncertainty.
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.
