Design And Experiment Of Water Mist And Heat Mist Double Spraying System For Plant Protection UAV

As one of the three major grain crops in China,corn is an important raw material in the field of industry and animal husbandry,and has high economic value.In the middle and late stages of corn growth,the plant is high,the leaves are dense,and the field environment is humid,often breeding a variety of pests and diseases.At present,the droplet size generated by the pressure or centrifugal nozzles used by the plant protection UAV is in a single range,and the control effect on complex pests and diseases is not good.Based on the theory of biological optimal particle size and the advantages of high efficiency prevention and control of plant protection drones,this study designed a water mist and heat mist double spraying plant protection drone by combining a pulsed heat mist machine and a centrifugal nozzle.The performance of the water mist and hot fog double spraying system under different working parameters was tested by experiments.The main research contents are as follows :(1)Complete the construction of water mist and heat mist double spraying plant protection UAV.Based on the theory of biological optimal particle size,this study proposes a scheme for plant protection UAV to carry pulse hot fog machine and centrifugal nozzle to realize double spraying of water mist and hot fog.Two diameter centrifugal nozzle systems are designed,and the corresponding whole machine structure and spray system are designed.The experimental results show that the whole machine can carry out plant protection operation safely and stably.(2)The atomization performance tests of water mist and hot mist spraying system were carried out respectively.The experimental results show that the droplet size of the hot fog spraying system increases first and then decreases with the increase of the horizontal distance L under different dosage.The droplet volume diameter is mostly less than 50μm,and the atomization performance is the best when the spraying flow rate is 800 ml / min.The two atomization plates of the water mist spraying system have good atomization effect,but the atomization plate with a diameter of 85 mm has better atomization effect under the same working parameters.Finally,the centrifugal nozzle with a diameter of 85 mm was selected as the executive component,and the spraying flow rate was 500 ml / min,and the rotation speed of the atomizing disc was 16000 r / min.(3)Set up a field to measure the droplet distribution test of the double spraying system at different flight heights.The results showed that the median diameter of the average number of droplets in the sampling area was about 50 μm,which was conducive to the comprehensive prevention and control of corn plant diseases and insect pests.With the increase of flight height,the deposition rate of droplets in the sampling area decreases continuously,which is 6.569μL / cm2,4.549μL / cm2 and 3.002μL / cm2 respectively.When the flight height is 4m,the uniformity of droplet deposition in the sampling area is the best.Two different methods were used to determine the effective width of the double spraying system at three flight heights.(4)Field experiments under different flight speeds were carried out in the middle and late stages of corn growth.The results show that the flight speed has little effect on the droplet size of the front and back of the blade,and the number of droplets on the back of the bottom blade is larger than the number of droplets on the back of the upper and middle leaves.The coverage of the front and back of the same sampling layer decreases with the increase of flight speed.The coverage of the opposite side of the blade at different flight speeds shows the same law,which is the largest at the bottom,the middle level and the smallest at the upper level.The penetration of droplets is the best when the flight speed is 2m / s.The droplet density on the front of the blade is greater than that on the back of the blade,and the uniformity of droplet distribution on the front of the upper and middle leaves is better than that on the back of the blade.The uniformity of droplet distribution on the front of the blade is the best at 3m / s,and the coefficient of variation is 27.7 %.