Design And Experiment Of Aerial Electrostatic Spray System Based On Space Loop

Spray pesticides with aerial electrostatic spray technology is not restricted by terrain and has high operating efficiency.The electrostatic repulsive force makes the droplets more atomized and deposited,and the droplet diameter got smaller.The electrostatic adsorption force can increase the deposition of droplets on crop targets,and the charged droplets can be adsorbed and deposited on the target back,which can reduce the loss of pesticides and improve the utilization rate.This study aimed to improve the deposition of droplets on the target back.An indoor and an aerial electrostatic spray systems based on six-rotor UAV were constructed.The physical model of aerial electrostatic spray based on space loop was proposed to provide a theoretical basis for achieving more precious droplet adsorption.The specific research contents are as follows:(1)The basic theory of electrostatic charge,atomization,electrostatics,and dynamics of electrostatic spray were analyzed.(2)An aerial electrostatic spray system was constructed,and an indoor suspended test bench was set up,plant targets and self-made simulated targets were used as spray objects to carry out exploratory tests of different spray methods.Through comparative experiments,the formation and direction of the current,it was concluded that the formation of the space loop was an important reason for the big improvement of droplets deposition on the back of the horizontal target.A physical model of electrostatic spray based on space loop was proposed,and which was proved to be feasible.(3)Digital cameras and high-speed video cameras were used to shoot charged droplet movements.Droplets trajectory capture and trajectory line drawing were performed in Phantom software,and the droplet motion status was classified.After analysis,the droplet absorption strength of the aerial electrostatic spray system in this study was confirmed according to the change of the droplet movement direction from90 to 180 degrees on horizontal target,which showed an electrostatic surrounding adsorption effect of the aerial electrostatic spray.(4)The back-front ratio of the droplet deposition density(BFR)on the horizontal target was used as the evaluation standard.The effects of spray time t,contact charging voltage U,and spray height h on the droplet adsorption and deposition of aerial electrostatic spray system were explored,and the maximum average BFR value was 158.8%,which have showed a good droplet adsorption and deposition effect on the target back.It is concluded that BFR has nothing to do with spray time,positive correlation with charging voltage,and negative correlation with spray height.(5)An infrared thermal imager was used to image the electrostatic spray mist cone,and it was found that the contact-charged spray had a obvious secondary atomization compared with the conventional spray.Three kinds of materials with different conductivity,such as ceramic,stainless steel and brass,and nozzles with different apertures were selected for electrostatic/non-static spray test.The fog cone angle increment after turning on static electricity was used as the evaluation index,and the electrostatic secondary atomization performance of the nozzle was obtained:brass>stainless steel>ceramic,aperture 0.5mm>1.0mm>1.5mm,which provided a reference for the nozzle selection of contact-charged spray.(6)The matching design of the aerial electrostatic spray system was carried out based on the high-tech M45 plant protection UAV.A six-rotor electrostatic spray UAV was successfully developed.After the static electricity was turned on,the density of the droplets on the target front was increased from 56.8/cm~2to 66.1/cm~2,caused an increase of 16.4%;the back was increased from 3.5/cm~2to 17/cm~2,caused a nearly fourfold increase,which was more significant than the front.The BFR increased from6.1%to 25.7%,indicating that the droplet adsorption performance on the target back was effectively improved.