Design And Test Of On-line Mixing System Of Sprayer

The annual use of pesticides in my country is about 310,000 tons,but the effective utilization rate is only 35%,which is also one of the main sources of agricultural pollution.The environmental and health problems caused by excessive and improper use of pesticides have become the consensus of the whole society,and the problem of efficient use of pesticides needs to be solved urgently.Compared with the traditional premixed drugs,the on-line mixing technology is more accurate,and there are no residual pesticides in the medicine box,which can improve the effective utilization rate of pesticides and is an important method to reduce the waste of pesticidesThis paper analyzes the common online drug mixing methods in the field of plant protection.Based on the principle of liquid mixing,a new online drug mixing device is designed from the perspective of increasing the drug-water mixing time and turbulence intensity.The device is designed for S-shaped elbow flow to increase the mixing time;a baffle is installed inside to increase the turbulence intensity.According to the working flow of the applicator,the structure size of the drug mixing device is initially given and a physical model is established.Use Fluent software to simulate the two-phase flow field of pesticide and water in the mixing device,and obtain a cloud map of pressure,velocity and pesticide volume distribution.The analysis of the cloud map shows that when the inlet pressure is 0.35MPa,each time a bend is passed,The volume fraction of pesticides increased by about 20%,indicating that the elbow design can improve the mixing performance.Design and build a drug mixing test device,and obtain the instantaneous image of the drug-water mixing process through the photographic imaging method,and confirm that the simulation can simulate the mixing process of liquid in the pipeline.Starting from the number of baffles and the arrangement of the baffles,four structural forms of mixing devices are designed,and the flow field simulation of the mixing process is performed to obtain the internal pressure,velocity and pesticide distribution cloud map,and obtain the pesticides at the outlet of different mixing devices.Liquid distribution,analysis of the influence of the baffle on the mixing effect and structural improvement,it is obtained that when the number of baffles is 4 and staggered,the energy loss is the least.Further study the influence of the distance between the inlet and the baffle L₁,the length of the straight tube L in the S-shaped elbow,the height H of the single-sided elbow,and the height H₀ of the baffle on the performance of drug mixing.By simulating the flow field of the drug mixing device,based on the uniformity of the pesticide volume distribution at the outlet,the optimal size relationship between the internal structures of the drug mixing device is obtained:L₁=2d,L=2d,H=2.5d,H₀=₄⁽（9）,under this size relationship,the drug mixing performance is the best.According to the working parameters of the sprayer with a spray width of 12 m,it is calculated that the pipe diameter d is not less than 32 mm to meet the flow requirements.Based on this parameter,design the online mixing device and select the plunger pump and peristaltic pump model and specification,Build a mixing control system and a spraying system.Finally,the performance parameters of the online mixed pesticide applicator were tested.In the case of different mixing ratios,the absorbance of the mixed liquid sprayed by multiple nozzles under the structure of multiple mixing devices is detected,and the concentration of the mixed liquid is obtained according to the concentration-absorbance curve,and its spatial variation coefficient is calculated.The test shows that The optimal structure size is obtained by simulation calculation,that is,the pipeline diameter d is 32 mm,the distance L1 between the injection port and the baffle is 64 mm,the straight pipe length L is 64 mm,the elbow height H is 80 mm,and the baffle height H0 is 8 mm,this structure size is the best mixing device.The device is further tested with a single nozzle.The test results show that after installing the mixing device,the spatial variation coefficient of the mixed liquid is less than 4%.For a single nozzle,the standard deviation of the spray liquid concentration is 6.73×10-4,indicating that the online mixing device can meet the requirements of different mixing ratios and field operations.Field tests also show that the system can meet the application requirements.