Design and experiment of an air-atomized, air-assisted and electrostatic orchard sprayer

Abstract：【Objective】For solving the problems of large labor intensity, poor work quality and pesticide drift of plant protection in grape production areas of our country, improving the orchard mechanization level and combining with the research status of anti-drift spray technology by domestic and foreign scientists.【Methods】The mechanical design theory and methods were applied and an air-atomized, air-assisted and electrostatic vineyard sprayer was developed in view of the characteristics of standardization vineyard in China, and the vineyard sprayer took the four-wheel tractors and crawler tractors as power and it was connected to tractors by the traction mechanism. The power was transferred to the rear components by the rear power output shaft and the universal joint shaft and the rear components such as the compressor, piston pump and fan were started. The main parts of the compressor, piston pump and fan and other compo-nents were fixed on the frame by the steady. The vineyard sprayer was made up of the air-atomized system, the air-assisted system and the electrostatic system. The compressor and the atomization nozzles were the core components of the air-atomized system. The compressor was selected in the light of the spray volume of the nozzles. The atomization nozzles were designed in accordance with the principle of air atomization. The air-assisted system was composed of the fan and the fan was chosen by the air flow and pressure. The number and size of the air outlets were determined by the different cultivation patterns of grapes. The electrostatic system was composed of the electrostatic generators and electromagnetic valves and its power was supplied by the battery of tractors. The charging way of the electrostatic system was contact charging and the high-voltage electrodes were connected directly to the atomization nozzles. The electrostatic generators were chosen because of the advantages which was that low-voltage power was required and the high-voltage static electricity was generated. According to the different structures of the grape trees, the vineyard sprayer could also spray partially and independently by controlling the different spray switches and could prevent the waste and pollution of pesticides. The spray capacity of nozzles was tested in the conditions of the different pressures. The droplets sizes were also tested when the air-assisted system was started and closed. The droplets sizes included the volume median diameter (VMD) of droplets and the number middle diameter (NMD) of droplets. The diffusion ratio (DR) was calculated by the VMD and the NMD. According to the NY/T 992—2006“air-assisted orchard sprayer operating quality”, the field experiment was carried out in the conditions of trellis, espalier and V form cultivation and a work speed of 1.5 m·s-1.【Results】The 9-195 A type centrifugal fan was chosen, and the number of the air outlets was determined to be 13 and the size of the air outlets was determined to be 20 mm×80 mm. The HX7.5 type compressor and the BSD50-1218 type electrostatic generators were selected, and the atomization nozzles of the patent number“2012 2 0330431.0”were designed and authorized. The VMD of the droplets was 110 μm, the NMD of the droplets was 80 μm and the DR was 0.73 when air-assisted system was closed. The VMD of the droplets was 72 μm, the NMD of the droplets was 60 μm and the DR of the droplets was 0.83 when the air-assisted system was started. The VMD and NMD of droplets were reduced with the help of the air-assisted system and the DR had an increase of 13.7%. The average adhesion rates of droplets in leaves on positive and negative sides outside the trees reached respectively 35.4% and89.4%, 92.0% and 44.0%, 86.1% and 34.4%, and the average adhesion rates of droplets in leaves on positive and negative sides inside the trees reached respectively 27.5% and 71.0%, 86.1% and 34.4%, 72.7% and 31.1%, when the electrostatic system was opened in the conditions of trellis, espalier and V form cultivation. The average adhesion rates of droplets in leaves on positive and negative sides outside the trees reached respectively 30.8% and 76.9%, 82.0% and 40.0%, 82.9% and 36.8%, and the average adhesion rates of droplets in leaves on positive and negative sides inside the trees reached respectively25.0% and 65.4%, 80.6% and 32.1%, 67.7% and 29.6% when the electrostatic system was turned off in the conditions of the trellis, espalier and V form cultivation. The average adhesion rates of droplets were increased respectively 14.9%, 16.3%, 10.0%, 8.6% and 12.2%, 10.0%, 6.8%, 7.3% and 9.4%, 12.5%, 7.4%, 5.1%. The electrostatic system increased the adhesion rates of droplets.【Conclusion】The combined technology of three spray technologies which included the air-atomized spray, air-assisted spray and electrostatic spray was used by the orchard sprayer and the orchard sprayer had the good atomization effect, reduced the sizes of droplets, enhanced the penetration of droplets, and improved the adsorption capacity of droplets.