Experimental Study On Deposition And Drift Characteristics Of Electrostatic Spray For Large-load Unmanned Helicopter

At present,the utilization rate of pesticides in China is 38.8%.The loss of pesticides causes the environmental pollution and the waste of natural resources.In order to meet the requirements of the agricultural development in china,it is urgent to develop advanced equipment and techniques.The downwash airflow generated by the rotor of a large-load unmanned helicopter can increase the momentum of droplets,which can improve the ability to resist natural wind disturbance.Also,it can enhance the disturbance to plants,which can make droplets enter the plant canopy and improve the control effect of pests and diseases.As a high-efficiency spray technology,electrostatic spray has been well applied in the field of agricultural plant protection in developed countries such as Europe and America because of its high atomization quality and good uniformity of deposition.In China,there is far-reaching significance to develop the aerial electrostatic spray technology which combines large-load unmanned helicopters with electrostatic spray technology and research the complex multiphase flow and deposition in electrostatic spray process.Through these researches,pesticide utilization rate and operation efficiency will be improved.In this research,an electrostatic spray system is designed according to FR-200 type large-load unmanned helicopter with a maximum load of 80 kg.The charging and spray characteristics of the electrostatic spray system were studied.Also,the prediction model of charge-to-mass ratio and droplet size was established.Field experiments were carried out to study the deposition and drift characteristics of the electrostatic spray for large-load unmanned helicopters.All of the researches provide a research foundation for developing high efficiency pesticide application technology.The main research results are as follows:1.An aerial electrostatic spray system for FR-200 type large-load unmanned helicopter was designed.Through the analysis of aerial electrostatic spray and the performance parameters of FR-200 type large-load unmanned helicopter,an induction electrostatic spray system was designed.The way of bipolar charge is used to balance the charge of the fuselage.The positive and negative electrodes of the high voltage electrostatic generator are connected with the electrostatic nozzles on both sides of the fuselage respectively.In this way,the equal and opposite voltage is applied to the nozzles on each side of the large-load unmanned helicopter.2.The performance of the electrostatic spray system was analyzed.The Farad cylinder and the laser particle size analyzer were used separately to measure the charge-to-mass ratio and the droplet size under different conditions.The change regulations of the charge-to-mass ratio and the droplet size with the change of charged voltage and spray pressure were achieved,which can provide reference for the selection of charged voltage and spray pressure of the electrostatic spraying system.3.The deposition characteristics of the electrostatic spray system which is suitable for FR-200 type large-load unmanned helicopter were studied.Based on the orthogonal test,the Box-Behnken response surface test was carried out to study the effects of the charged voltage,the flight velocity and the flight height on the deposition amount and the deposition uniformity of electrostatic spray on a large-load unmanned helicopter.By the way of increasing charged voltage or decreasing flight velocity and height,deposition amount can be increased.While increasing charged voltage and height or decreasing flight velocity,deposition uniformity will be improved.The mathematical models of the deposition amount and the deposition uniformity on the charged voltage,the flight velocity and the flight height were established by using Design-Expert software.On this basis,the optimization scheme of operation parameters is put forward,and the test is carried out to verify it.4.The drift characteristics of the electrostatic spray system which is suitable for FR-200 type large-load unmanned helicopter were studied.The orthogonal test was carried out to study the effects of the charged voltage,the flight height and the velocity of lateral wind on the drift of the electrostatic spray on large-load unmanned helicopters.By the way of increasing charged voltage or decreasing flight height and lateral wind velocity,droplet drift will be reduced.The mathematical model of the drift was established with the center distance of droplet mass and the droplet drift rate as objective functions,which can be used to predict the drift of droplets under different operating conditions.