| The air jet angle and the nozzle mounting angle are important factors affecting the air delivery effect of the inclined and air-assisted boom spray system.As an air curtain system with adjustable airflow angle and nozzle installation angle,the inclined and air-assisted boom spray system can effectively reduce the drift of pesticide droplets and improve the control effect of pests and diseases.Compared with the previous air curtain sprayer spray system,the system has stronger anti-splash and air transfer effects for pesticide droplets.At present,the design and research of the domestic air-assisted boom sprayer application system mostly stays in the experience design stage,and the influence of the airflow injection angle of the air curtain system and the nozzle installation angle on the spray flow field is rarely considered.Based on many domestic and foreign research data,this paper uses the Computational Fluid Dynamics(CFD)numerical simulation technology to study the spray flow field and droplet drift law of the inclined air-assisted boom spray system.Through the experimental research on the numerical analysis results,the deposition and drift law of the droplets in the inclined air-assisted boom sprayer system were obtained,and the optimal working parameter combination suitable for the system was provided.The main research contents include:(1)The two-phase flow numerical model analysis method of the air-assisted boom spray flow field was summarized.According to the numerical analysis characteristics of the spray flow field of the inclined air-assisted boom spray system,the basic theory and applicability of the two-phase flow model,continuous medium turbulence model and particle model suitable for the spray flow field analysis requirements were systematically analyzed and expounded.It provides a reference for the numerical analysis of the gas-liquid two-phase flow field of the inclined air-assisted boom.(2)The experimental device of the inclined air-assisted boom spray system was designed,and the CFD numerical model of the spray flow field was established.The numerical analysis of the airflow field of the inclined air-assisted boom spray system was carried out,and the test of the airflow distribution of the air-assisted outlet was carried out.The numerical analysis results of the airflow field are compared with the experimental measurements.Research indicates that when the axial fan speed is 500r/min,1000r/min,1500r/min and 2000r/min,the corresponding air curtain outlets have average speeds of 3.4m/s,6.9m/s,10.1m/s and 13.3m/s.The numerical analysis results of the airflow velocity of the air curtain outlet are basically consistent with the trend of the experimental measurement results.Therefore,the numerical analysis model established in this paper can accurately simulate the flow field of the inclined air curtain sprayer spray system.(3)The numerical analysis of the gas-liquid two-phase flow field of the inclined an inclined and air-assisted boom spray system was carried out.The drift rate of the droplets and the center distance of the sediment mass were used as the evaluation indexes of the application quality.The effects of natural wind,fan speed,spray pressure,air jet angle and nozzle mounting angle on the drift rate of droplets and the center distance of deposition mass were analyzed.The orthogonal test design scheme was designed by five factors and four levels,and the numerical calculation results were analyzed and summarized by the range analysis.The results show that the factors affecting the drift rate of droplets and the center distance of sedimentary mass are from the main to the order: natural wind speed,nozzle installation angle,fan speed,spray pressure,air jet angle.When the drift rate is used as the evaluation index,the optimal operating parameters of the inclined air curtain sprayer system are: natural wind speed is 0,fan speed is 2000r/min,spray pressure is 0.5Mpa,air jet angle is 30°,and nozzle installation angle is 7.5°.(4)The design of the inclined and air-assisted boom spray system float drift and deposition test bench was designed.According to the results of the above numerical analysis,the experimental research on droplet deposition and drift of the inclined air curtain spray bar spray system under different working conditions was carried out.A horizontal fog meter device was used in the test for collecting the droplets and calculating the drift rate,and then the numerical calculation was compared with the drift rate of the test under different working conditions.The results show that there is a certain deviation between the numerical analysis results of the drift rate and the test results,the maximum absolute error is 15%,and the maximum relative error is 37.7%.The variation trend of the droplet drift rate of the numerical analysis is basically consistent with the test results.The numerical model can accurately reflect the droplet deposition and drift law of the inclined and air-assisted boom spray system,which provides a reference for further research. |
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