Optimization And Test Of Spray Parameters For Target Screen With Variable Volume Sprayer

The traditional target variable sprayer can detect the distribution and difference of diseases,pests and weeds in the target area,so as to implement real-time,non-uniform and non-continuous precision spraying,and achieve the on-demand pesticide application.But the target variable spray operation is affected by natural wind,resulting in incomplete matching of target area and droplet deposition area.Adding air curtain system to target variable sprayer can generate air curtain airflow to restrain the drift of natural wind and increase the target performance of droplet.However,the changing natural wind and the actual situation of the complex target area make it difficult for the target variable spraying operation assisted by the air curtain.It is urgent to find out the droplet deposition and target distribution law of the target variable spraying operation under the influence of the natural wind and the air curtain.Therefore,based on a large number of domestic and foreign literatures,a wind screen variable sprayer which can adjust the airflow rate of the air curtain and the volume of the spray nozzle has been developed.The droplet deposition and the target distribution law in the gas-liquid two-phase flow field of the wind curtain type spray rod are studied by experiments,numerical simulation and parameter optimization.The optimal operating point of target variable application was obtained and verified by field test.The main contents and conclusions are as follows:The main structure includes sprayer chassis,boom assembly,spray system,air curtain system and vision system.The test results of the sprinkler spray volume uniformity of the wind screen variable spray nozzle and the wind speed uniformity of the wind curtain outlet meet the design requirements,and can be used for subsequent pesticide application.The wind tunnel test of the wind screen variable nozzle sprayer shows that when the natural wind speed increases,the increase of the air curtain rate can increase the droplet deposition,but the anti-floating effect tends to be stable.When the natural wind speed increases,the volume of droplet spray can increase the droplet deposition,but the droplet deposition rate increases.The deposition performance of the composite is decreasing.The target performance test of the wind screen variable nozzle sprayer is carried out.The test results show that when the natural wind speed increases,the airflow rate can reduce the center distance of droplet deposition quality,but the decreasing trend tends to be stable.When the natural wind speed increases,increasing the spray volume ratio of the nozzle can increase the deposition mass center distance of the droplets,but the targeting performance of the droplets decreases gradually.Using Ansys Fluent fluid mechanics software,discrete phase model and standard model were used to simulate the movement process of droplet in the gas-liquid two-phase flow field of the wind curtain type spray rod,and the velocity distribution cloud map and droplet trajectory were obtained.The trajectory shows that the velocity of the droplet itself is gradually offset by the air resistance,and drift occurs due to the influence of the horizontal natural wind.The air flow of the wind curtain can accelerate the movement of the droplets in the vertical direction,shorten the stagnation time of the droplets,and significantly reduce the drift loss of the droplets.The comparison between the numerical simulation results and the mass center distance of droplet deposition in the target performance test shows that the two sets of data are highly consistent.It is proved that the air curtain type spray rod spray gas-liquid two-phase flow field model is reasonable,and it can accurately simulate the spraying process of the wind screen variable nozzle sprayer on target variable.The response surface method is applied to optimize the numerical simulation of two phase flow field of the wind curtain type spray rod.The two response values are introduced: the anti-drift coefficient F and the droplet deposition quality center distance D.According to the experimental design of response surface method,the optimal variables and response values were fitted to obtain the regression equation and the interaction effect of multiple factors on the influence of drift coefficient F and the distance between the droplet deposition mass centers D.The interaction effect of many factors shows that the anti-drift coefficient f increases with the increase of air flow rate.When the natural wind speed,the volume ratio of spray nozzle is at zero level,and the air flow rate is at high level,the anti-drift performance of the droplet is the best.When the natural wind speed and the volume ratio of spray nozzle are at zero level and the air velocity is at high level,the deviation between the deposition area and the target area is the smallest,and the target distribution performance is the best.By using the optimization algorithm,the maximum value of F and the minimum D value of droplet deposition mass center are obtained simultaneously.The best combination of spray parameters is obtained when the natural wind speed is 3.72m/s,the nozzle volume is 0.00815kg/s and the airflow rate is 16.1m/s.At this time,f=80.77%,D=163.73 mm Field experiments show that the operating point is very close to the optimal spray point of field test.It is proved that the method of multi conditions for numerical simulation results is reasonable,it provides a theoretical basis for optimizing the control strategy of target spray operation.