Objective  This study was aimed to design a air-assisted sprayer for the wind requirement of fruit tree with Y-typed trellis, explore the spraying regularity of applying the machine to such type of tree, and provide references for designing plant protection equipment for the orchard with new planting technology.

Method  According to wind demanding characteristic of the Y-typed canopy of pear trees, a special-shaped duct was designed. The duct could be adjusted according to different conditions, and the range of spray could cover tree canopy completely. The whole machine was configured, and the fan speed was adjusted using a stepless speed regulation pulley. The operating speed, outlet wind speed and height difference between the outlet and the middle of canopy were taken as test parameters, and the droplet coverage rate on target, the droplet deposition of target and the droplet deposition on ground were taken as evaluation indexes. The Design-Expert software was used to establish response surface, analyze the influence of parameters on the indexes, and optimize the operating parameters of the machine.

Result  The optimization results showed that when the operating speed was 0.8 m/s, the outlet wind speed was 22 m/s and the height difference between the middle part of the air outlet and the middle part of the pear canopy was 5.1 cm, the droplet coverage rate on target was 39.79%, the droplet deposition was 9.89 µL/cm², the droplet deposition on ground was 5.41 µL/cm², and the ratio of effectively attached liquid was 60.1%.

Conclusion  This machine can satisfy the requirements of orchard operation with good spraying effect. It provides a reference for the design of sprayer for rack type orchard and the optimization of machine parameters.