| In recent years,agricultural plant protection rotor UAV(unmanned aerial vehicle)have been rapidly and widely used in China due to their small size,flexible operation,unrestricted terrain,and no need for special take-off and landing sites.When the rotary UAV is used for plant protection spraying,a significant feature is that in addition to powering the body,the high-speed rotating rotor also generates a strong downwash airflow that moves downward and interacts with the crop canopy.Then the crop canopy is forced to collapse around wind field action position,and forming a conical vortex shape.After spraying from the nozzle,the pesticide droplets is easily drawn into the downwash airflow during the sedimentation process,the movement state of the droplet is almost completely determined by the rotor underwash field during this time.When the rotor downwash airflow field is effectively applied to the crop canopy,the droplets involved in it may deposit on the crop canopy.And the vortex states is a direct characterization of the interaction between the downwash rotor airflow and the crop canopy.Therefore,the study of vortex plays an important role in improving the droplet deposition effect.At the same time,the droplet deposition influencing factors of the rotor UAV airflow application can be attributed to the three core influencing factors of vortex states,droplet size and crop phenotypic parameters.The research on the three factors is also of great significance to improve the airflow application effect of the rotor UAV.This project is mainly based on the airflow application of rotor UAV,and rice is selected as a research crop.According to the analysis of the research status of the factors affecting the droplet deposition effect at home and abroad,the relationship between different vortex states and the droplet deposition distribution characteristics was explored.The importance of the influence of the three core factors of vortex states,droplet size and crop phenotype on the droplet deposition effect under the rotorcraft UAV airflow application was also analyzed.The experimental research is mainly carried out from the following aspects:(1)Design related experiments to explore the relationship between vortex morphology and droplet deposition effect.Firstly,the nozzle performance was tested in a wind tunnel to enhance the reliability of the test results,and then related field tests were conducted to investigate the droplet deposition effect under three states of obvious vortex,small range vortex and no vortex.The results showed that the formation of vortex had a significant effect on the droplets deposition effect,and the more obvious the vortex state,the better the droplet deposition effect.(2)Three core influencing factors affecting the droplet deposition effect under the rotor UAV airflow application: vortex state,droplets size and crop phenotypic parameters were optimized.An orthogonal experiment was designed to explore the importance of the three factors influencing on the droplet deposition effect.The results showed that the major to minor effects of the three factors on the droplet deposition volume were vortex state,droplet size,and crop phenotypic parameters,and that of droplet deposition uniformity were vortex states,crop phenotypic parameters,and droplet size.Vortex states was the most important factor for droplet deposition amount and deposition uniformity,and had a significant effect on both.But there are some differences about the importance of droplet size and crop phenotypic parameters on droplet deposition amount and deposition uniformity.In addition,the tests with a better droplets deposition amount had a poorer droplet deposition uniformity,while the tests with a better drop deposition uniformity had a poorer droplet deposition amount.Therefore,it is necessary to consider the droplets deposition amount and droplets deposition uniformity comprehensively in the rotor UAV airflow application to achieve better droplet deposition effect. |
