Development And Test Of V-shaped Orchard Anti-drift Sprayer With Multi-airflow Cooperation

Droplet drift and canopy deposition are important indicators to measure the effect of spraying machinery.At present,most domestic orchard plant protection operations use air-driven sprayers,which send droplets to the target through a single auxiliary airflow,which improves the internal fog of the target to a certain extent.However,the droplet coverage on the backside of fruit tree leaves was still low,and pesticide drift was wasteful.Therefore,it is of great theoretical and practical significance to carry out the experimental research on the design of multi-airflow synergistic orchard anti-drift sprayer and its droplet deposition characteristics.The main research contents are outlined below.（1）According to the fruit tree planting mode,the overall scheme of the V-shaped orchard anti-drift sprayer with multi-airflow cooperation is proposed.The main air duct is arranged in a V shape in the horizontal direction;according to the orchard spraying standards,the main structural parameters of the air duct height and V-shaped opening are calculated to be 2.3 m and 27°respectively,and the working parameters of the total spray flow,air volume and air pressure are 14.4 L/min,2.1 m~3/s,1630 MPa respectively;static and modal analysis of the frame is carried out,the maximum stress is 36.4 MPa,and the first-order natural frequency is38.803 Hz,which meets the design requirements and provides a basis for the establishment of subsequent simulation models.（2）According to its structural design,a numerical model of the spray field from the spray device to the canopy area of the fruit tree is constructed;through the Fluent simulation,when the natural wind speed is 4 m/s and the V-shaped wind speed is 20 m/s,the maximum deviation of the spray airflow under the coordination of multiple airflows is obtained.The drift angle is only 3.5°,which is 82.1%lower than that of the single airflow,indicating that the V-shaped wind field has a better anti-drift effect;the drift degree is described by the airflow speed between the rows of fruit trees.When the V-shaped wind speed is greater than25 m/s,the inter-row airflow speed is negative,and the fog droplets drift in the opposite direction.Therefore,the optimal V-shaped wind speed range is determined to be[15 m/s,25m/s].（3）The droplets are regarded as spherical particles,and the force of the droplets in the multi-air flow field is analyzed,and the displacement function of the droplets in the flow field space is deduced based on the particle dynamics equation.The smaller the droplets,the more obvious the drift between rows;when the natural wind speed is 4 m/s,the V-shaped wind speed is 20 m/s,and the spray pressure is 0.8 MPa,the proportion of drifting droplets is33.2%,indicating that the drift is serious.The optimal interval of spray pressure is determined to be[0.4 MPa,0.6 MPa]respectively.（4）Numerical simulation of droplet deposition was carried out based on the Fluent DPM model,and the spatial trajectory of droplets from the nozzle to the canopy area of fruit trees was simulated.The influence of pressure on the drift distance of the droplet deposition center;the orthogonal polynomial regression method was used to establish the drift distance model of the droplet deposition center under the coordination of multiple airflows.According to the spray requirements,the cross wind speed was 4 m/s and the spray pressure was 0.5 MPa,the V-shaped wind speed is taken as 23.3～25.6 m/s,which provides a basis for the optimization of prototype parameters.（5）Trial-produced prototypes for field drift-proof performance verification and droplet deposition characteristics tests.The results show that when the cross-wind wind speed is3m/s,the droplet deposition density under the synergistic effect of multiple airflows increases by 28.7%compared with a single airflow,and the drift decreases by 21.8%;the order of significant effects on droplet deposition characteristics is from large to small.The order is:V-shaped wind speed,cross-wind wind speed,and spray pressure.When the cross-wind wind speed is 2 m/s,the spray pressure is 0.52 MPa,and the V-shaped wind field wind speed is21.8 m/s,the droplet deposition volume is 4.72μL/cm~2,basically consistent with the prediction model.