Spray drift characteristics test of unmanned aerial vehicle spray unit under wind tunnel conditions

Since the 2010s,unmanned aerial vehicle(UAV)sprayer was applied more and more widely for low-volume aerial pesticides spraying operations in China.However,droplets from the UAV sprayer have a higher drift risk due to more fine droplets sprayed and a higher flight height than ground sprayers.Study on UAV spray drift has been a new hot spot within the field of pesticide application technology.Most of previous studies used direct field methods for spray drift,but the meteorological conditions in field were unstable and uncontrollable,and drift research under an actual operation state in wind tunnel has not been reported.Therefore,25 treatments of wind tunnel measurements and droplets spectrum tests of 10 models of nozzles were conducted to explore the influence factor on spray drift characteristics of UAV chemicals application in this study.A spray unit with a rotor of UAV was innovatively installed in wind tunnel,and the airstream from the wind tunnel was regarded as the relative moving natural wind to simulate the flight status.The airborne and the sediment spray drift was measured to study the effects of the nozzle type and size(flat fan,hollow cone and air-inclusion nozzles),flight speed,adjuvant(DRS-60,Y-20079,MF and G-611)and meteorological parameters(20°C&40%,20°C&80%,30°C&40%and 30°C&60%).The drift potential(DP)and the drift potential reduction percentage(DPRP)in vertical and horizontal directions were obtained for each test.Both nozzle type and size had an impact on the spray drift potential obviously by affecting the droplet size and the ratio of fine droplets,and the regression linear models between DPRPV/DPRPH and DV50,V75 were established(R2=0.934/0.925).Flight speed also had a significant effect on the spray drift characteristics,and reducing the flight speed could increase the DP effectively.Adding spray adjuvants could affect the DP under experimental meteorological parameters,and the anti-drift performance ranked in the order of DRS-60>MF>Y-20079>G-611.Recommendations were proposed in order to reduce the spray drift for UAV sprayer’s operation.These findings can contribute to provide guidelines and technical support for the wind tunnel spray drift tests of UAV and the field operation regulation of unmanned aerial PPP application.

An effective spray drift-reducing method for a plant-protection unmanned aerial vehicle

A spraying system for a plant-protection unmanned aerial vehicle(UAV)was designed to reduce spray drift.A custom low-speed wind tunnel was constructed to generate a wind speed ranging from 0 to 5.92 m/s.The results showed that the wind speed was attenuated with an increase in distance.To compensate for the attenuation,a linear-fitting model was adopted.Then,the relationship between the spraying pressure and atomization rate was analyzed,and a fuzzy algorithm was adopted to adjust the spraying angle and pressure according to the wind speed and its changing rate.Finally,an evaluation of the proposed system in the compensated wind tunnel was conducted,and the drift distance was reduced by 33.7%compared with the system without adjustment of the spraying angle and pressure.

Spray drift characteristics of pulse-width modulation sprays in wind tunnel

Pulse-width modulation(PWM)sprays can improve flow accuracy by adjusting duty cycle and frequency signal which accurately controls the relative proportion of opening time of solenoid valve.The objective of this research was to determine the impacts of PWM duty cycle and frequency on spray drift characteristic.Spray tests were conducted in a wind tunnel with a PWM variable-rate spraying system.The airborne drift and sediment drift were determined with tracer method,and the drift potential reduction(DPR)compared with reference condition of 100%duty cycle at vertical profile and horizontal planes were calculated,respectively.The results show that,at a given frequency,droplet size decreases with the increase of duty cycle,the main reason is that the liquid does not reach full pattern development at lower duty cycle.Duty cycle has a greater impact than the frequency on spray drift,the influence weights of duty cycle on airborne drift and sediment drift were 88.32%and 77.89%,respectively.At a lower PWM frequency,in addition to the droplet size,the spray drift may be affected by the pulsed spray pattern.From the perspective of reducing spray drift,it is recommended that the PWM duty cycle should be set in the range of 20%-70%to reduce the potential drift in PWM sprays.This research provides a pesticide drift reduction scheme for variable spraying technology,which can serve as a theoretical basis for PWM parameter selection.

Performance characterization on downwash flow and spray drift of multirotor unmanned agricultural aircraft system based on CFD

In recent years,multi-rotor Unmanned Aerial Vehicles(UAVs)have been employed in the field of plant protection in China.Spray drift has been considered a major impact in agriculture aerial spraying,and spray quality in the application of plant protection products.The downwash including wake vortices and downward wind field plays a major role in the dispersal and deposition of pesticide spray released by nozzle(s)equipped in aircraft.Differ from the fixed-wing UAV,the downwash flow of multi-rotor UAV was result from the rotation of rotor.Therefore,a study on off-target drift and ground deposit concerning the rotor rotation was simulated through a series of Computational Fluid Dynamics(CFD)simulations to obtain the influence of downwash.The discrete Phase Model(DPM)was taken to simulate the motion of droplet particles since it is an appropriate way to simulate discrete phases in flow field and can track particle trajectory.In this study,the parameters of CFD simulations were acquired by three kinds of actual replicated experiment.The simulation analysis mainly obtains the droplet drift and deposition rule,the influence of eddy current,and downwash flow caused by the rotor rotation.The results showed that the downwash distribution below different rotors was different owing to the flight angle of inclination,“behind”is the greatest,“middle”is secondly,and“forward”is smallest in value(behind,middle,and forward represent three regions below rotors along flight direction).According to the simulation results,two methods of reducing droplet drift were put forward and specific simulations were carried out to prove their feasibility.The results of this study can provide theoretical support for improving the spray quality of UAV and reducing the drift of droplets.

Development and Evaluation of an Optical Sensing System for Detection of Herbicide Spray Droplets

Real time monitoring of herbicide spray droplet drift is important for crop production management and environmental protection. Existing spray droplet drift detection methods, such as water-sensitive paper and tracers of fluorescence and Rubidium chloride, are time-consuming and laborious, and the accuracies are not high in general. Also, the tracer methods indirectly quantify the spray deposition from the concentration of the tracer and may change the drift characteristics of the sprayed herbicides. In this study, a new optical sensor system was developed to directly detect the spray droplets without the need to add any tracer in the spray liquid. The system was prototyped using a single broadband programmable LED light source and a near infrared sensor containing 6 broadband spectral detectors at 610, 680, 730, 760, 810, and 860 nm to build a detection system for monitoring and analysis of herbicide spray droplet drift. A rotatory structure driven by a stepper motor in the system was created to shift the droplet capture line going under the optical sensor to measure and collect the spectral signals that reflect spray drift droplets along the line. The system prototype was tested for detection of small (Very Fine and Fine), medium (Medium), and large (Coarse) droplets within the droplet classifications of the American Society of Agricultural and Biological Engineers. Laboratory testing results indicated that the system could detect the droplets of different sizes and determine the droplet positions on the droplet capture line with 100% accuracy at the wavelength of 610 nm selected from the 6 bands to detect the droplets.

Characterization of spray deposition and drift from a low drift nozzle for aerial application at different application altitudes

A complex interaction of controllable and uncontrollable factors is involved in aerial application of crop production and protection materials.Although it is difficult to completely characterize spray deposition and drift,these important factors can be estimated with appropriate sampling protocol and analysis.Application height is an important variable influencing off-target spray drift,but this variable has not been easily measured or logged.A custom-configured aircraft-mounted laser with logging capabilities makes this possible.This study was designed to investigate droplet size and deposition characteristics of a low drift CP flat-fan nozzle at application altitudes 3.7 m,4.9 m,and 6.1 m.In the study,CP flat-fan nozzles were set to a downward angle of 30 degrees applying a mixture of water,Syl-Tac®adjuvant,and Rubidium Chloride(RbCl)tracer at a 28.5 L/ha application rate.Spray droplets were collected using water sensitive paper(WSP)cards placed in the spray swath.Mylar sheets were also placed in the swath and downwind for drift sampling.Statistical analysis indicated that median droplet diameter as determined by WSP in the spray swath was not significantly influenced by spray application height.Similarly,statistical analysis also indicated that concentration of RbCl tracer from Mylar samplers in the spray swath was not significantly influenced by application height.Application height had a significant effect on spray deposition from drift samplers,along with wind direction and relative humidity.Final results for drift samplers may have been influenced by shifts in wind direction that altered the relationship between orientation of samplers and wind.

植保施药机械喷雾雾滴飘移研究进展

中国农药产品80%以上通过喷雾方式施用,药液从喷头到靶标作物过程中产生的随风飘移和蒸发飘移是农药造成人畜健康风险、生态环境破坏的重要因素之一。随着航空施药技术的发展,解决或减少喷雾雾滴飘移的问题成为施药技术研究的重点和热点。基于此,本文分别从喷雾雾滴(尺寸分布、黏度、表面张力、蒸气压、挥发性、密度等)、喷雾模式(喷头类型、喷雾速度和高度、喷施方法)和外界条件(风速、风向、温度、湿度、气流等环境条件和操作人员技术水平等)等方面系统分析了产生雾滴飘移的主要原因;同时详细综述了采用田间试验、室内试验、计算机模拟及新型测试技术测定喷雾雾滴飘移的优点及局限性,针对植保无人飞机施药,提出应通过室内测定、田间试验与计算机模拟相结合的方式开展雾滴飘移研究。在此基础上分析并总结了从改变雾滴的运动方式、理化性质等方面直接控制和从田间布局间接控制的喷雾雾滴飘移风险控制技术。

Drift and deposition of pesticide applied by UAV on pineapple plants under different meteorological conditions

Spray drift has always been a focus research area in the field of unmanned aerial vehicle(UAV)application.Under the fixed premises of UAV operating parameters,such as height,speed and spraying liquid,the droplet drift is mainly affected by meteorological conditions.In this research,the spray drift and deposition tests were conducted using a QuanFeng120 UAV in a pineapple field under various different meteorological conditions.The experimental results showed that with the changes of UAV operating height and wind speed,the start position of the in-swath deposition area changed 4 m in the extreme situation.The percentage of the total spray drift was from 15.42%to 55.76%.The position of cumulative spray drift that accounted for 90%of the total spray drift was from 3.70 m to 46.50 m relative to the flight line.According to the downwind spray drift curve,the nonlinear equations of the same type under the four operating conditions of the UAV were fitted.The spray drift and the deposition of UAV application were significantly affected by different meteorological conditions and UAV operating heights.The results could provide a theoretical basis for UAV spraying in pineapple plants and support for spray drift control and prediction.

Drift potential of UAV with adjuvants in aerial applications

The reduction of pesticide aerial spraying drift is still one of the major challenges in modern agriculture.The aim of this study was to evaluate the drift potential of different types of unmanned aerial vehicle(UAV)and adjuvant products for reducing spray drift in aerial applications.Three types of UAV(3WQF120-12 and 3CD-15 fuel oil powered single-rotor UAV and HY-B-15L battery powered single-rotor UAV)were selected in this study with regular application parameters to compare each spray drift,and 3WQF120-12 fuel oil powered UAV was selected to quantify spray drift of 6 adjuvants dissolved in water under field conditions.Solutions were marked with brillant sulfoflavin dye(BSF)at 0.1%.Petri dishes and rotary impactors were used to collect airborne and sediment drift,respectively.Drift deposits were evaluated by spectrophotometry in order to quantify deposits.The results showed that when the flight height was 1.5-2.0 m above the crop at the flight speed of 4-5 m/s and the average wind speed of 1.63-1.73 m/s,3WQF120-12 fuel oil powered UAV had lower drift potential than the other two types;DV0.5 and percentage of droplets with diameter≤75μm had very significant effects on spray drift percentage(p=0.01);the risk of drift in agricultural spraying could be significantly decreased not only by reducing the percentage of fine droplets but also by changing droplet spectra.Compared to water,Silwet DRS-60,ASFA+B,T1602,Break-thru Vibrant,QF-LY and Tmax could reduce by 65%,62%,59%,46%,42%,and 19%spray drift,respectively.when water without adjuvants were sprayed,90%of drift droplets were located within a range of 10.1 m of the target area while with 0.8%Silwet DRS-60 adjuvant in water,the distance was shortened to 6.4 m.