| The drift of pesticide droplets will reduce the utilization rate of pesticides,weaken the control effect,and endanger the health of agricultural workers.In the process of pesticide spray,the impact of the collision behavior of the droplets in the high-density droplet group on the spatial operation law cannot be ignored.In response to the need for pesticide spraying to reduce drift and increase efficiency in agricultural production,this paper uses numerical simulation methods to obtain the spatial operation of droplets under different pesticide liquid properties and spraying operating conditions,and quantitatively analyzes the main collision area,the impact of collision behavior on droplet diameter distribution and drift ratio under various conditions.The coalescence ratio of the droplet collision process and the contribution rate of collision behavior to drift reduction under various conditions are calculated.By changing the pesticide liquid properties or spraying operating conditions to control the collision process effectively,an efficient and feasible pesticide spraying plan is proposed to guide the field application process,and to achieve the goal of reducing drift and increasing efficiency.Firstly,the influence of the pesticide liquid properties on the droplet diameter distribution and collision behavior is discussed.The discrete phase model coupled with random collision model was used to simulate the spatial operation of different pesticide droplets,and the effects of viscosity and surface tension on the initial diameter distribution,the collision behavior,and the drift ratio of the droplet were investigated.The results show that by adjusting the viscosity at 0.001～0.010 Pa·s or the surface tension at 0.042～0.060 N/m,more large droplets can collide and separate into small droplets which are easy to deposit.The drift ratios are respectively25.33～30.00% and 34.47～43.67%,with good absorption effect of canopy deposition.Secondly,the influence of spraying conditions on droplet collision behavior and drift ratio is explored.Through statistical analysis of droplet diameter and velocity data on different heights,the influence of spray angle,spray height,wind speed on droplet deceleration area,main collision area,and average diameter change before and after collision are investigated respectively,according to the three sections of initial section,operation section,and deposition section.The results show that adjusting the spray angle at 40～60° or adjusting the spray height at 0.7～0.9 m can increase the probability of small droplets colliding and coalescing,and the drift ratios are 35.33～48.27% and 20.60～38.49%,respectively.Choose to apply pesticide under the weather conditions with wind speed ≤ 3 m/s,which can increase the coalescence ratio during the collision process,the drift ratio is controlled below 48.27%,and the deposition diameter is conducive to plant absorption.Finally,the influence of pesticide liquid properties and application conditions on the coalescence ratio and drift ratio are comprehensively considered,and taking the total coalescence ratio during the collision process as a quantitative indicator,the contribution rate of various factors to reduce drift is ranked.The contribution rate of various factors based on the collision and coalescence is as follows: wind speed(16.65%)> spray angle(14.51%)> surface tension(9.93%)> spray height(8.03%)> viscosity(7.43%);The influence of the changes of various factors on the droplet collision behavior is as follows: wind speed(15.74%)>surface tension(5.94%)>spray height(5.91%)>viscosity(3.79%)>spray angle(3.37%).By comprehensively considering drift ratio and coalescence ratio in the collision process,combined with the canopy deposition effect,the droplet collision behavior is controlled according to priority,and a drift reduction scheme for different crop growth periods and extreme spraying scenarios is proposed. |
PDF Full Text Request