Studying The Influence Of Spray Atomization Process And Cotton Canopy Structure On The Droplet Deposition

China is a big country which produces a lot of cotton and textile. The annual output of cotton is6-8million tons, ranking first in the word; the annual output and export of textile and apparel is also the first in the word, therefore, the consumption of cotton in China also ranks first in the world with the annual consumption of about10million tons. As much as possible to meet the domestic demand of cotton, it is necessary to protect cotton well during its whole growing period by plant protection machinery for improving cotton yield level on limited cultivation area. However, a wide range of pests and pathogens threat the production of cotton which is an important cash crop in China. To protect the cotton against the pests and pathogens, farmers always spray a lot of pesticide onto the cotton and spray frequently. Yet the cotton leaf is easy to wet, high application rate causes spray droplets running off the leaf surface, resulting in economic loses, pesticide waste and environmental pollution. Therefore, this paper focused on how to improve the effective utilization of pesticide on cotton. The influence of spray atomization process and cotton canopy structure on the droplet deposition on cotton leaf was investigated by studying the cotton as object, the different type nozzles which can atomizing different size droplets and the different canopy structures in cotton seeding stage and flower and boll stage as influence factors. The results of this study would be helpful to find suitable nozzle for each cotton growth stage achieving the best droplet deposition amount in the cotton canopy, guide the actual field spraying and improve the utilization of pesticides. In this study, from the perspective of theory, firstly analyzed the mechanism of atomization and droplet deposition, established the equation of droplet size distribution and the prediction models of bouncing and shattering after droplets impacting on the target leaf; then tested the nozzle atomization process by droplet size analyzer and PIV (Particle Image Velocimetry) system to confirm every coefficient in the equation and imaged the droplet impacting on the target leaf using High-speed video system to verify the two prediction models; finally determined the optimum droplet size and velocity range (stood by nozzle type) for each cotton growth stage by the means of observing the cotton canopy in every growth stage and testing the droplet deposition on cotton. The main conclusions are as follows:(1) In this paper, the prediction models of droplet bouncing and shattering were established based on the theory of droplet deposition and energy conservation. Verified by the High-speed video system experiment and Fluent software simulation, the two models was able to effectively predict the droplet behavior after impaction on the target leaf according to the size and velocity of that droplet.(2) The nozzle atomization process was tested by PIV system and Spraytec droplet size analyzer, the results show that:for the tested nozzles, the atomization parameters among different nozzle types were significantly different. The droplet size distribution equations established in this paper can accurately describe and predict the droplet volume median diameter distribution in the longitudinal section of the spray fan for all tested nozzles. (3) The cotton canopies in different growth stages were observed and the droplet deposition on the cotton leaf was tested, it was found that02nozzles in the tested nozzles were more suitable for the pesticide application in the cotton seeding stage; ST110-03nozzle was a better selection than other tested nozzles for the pesticide application in the cotton flower and boll stage achieving the higher deposition amount and droplet penetration.(4) According to the record of cotton growing process, a cotton growth model was established; the virtual cotton structure in this growth model was realistic. In this paper, it was first proposed to select appropriate type nozzle for the corresponding cotton canopy based on the droplet size and velocity range. That would allow users to spray efficiently and provide technical support for agricultural production.