Effect of fan power supply frequency on deposition of air-assisted sprayer

The distribution of droplet deposition and spraying swath is affected by the fan speed of air-assisted sprayer. Taking the D400 air-assisted sprayer as the experiment platform, the spraying experiment was carried out by using 1 g/L concentration solution with colorant Rhodamine-B, instead of pesticide. The droplet deposition on sampling points under variable fan frequency was calculated by using the fluorescence spectrophotometer. Test results showed that the three deposition peak areas in axial direction of the spray tube were formed due to variable nozzle locations relative to different height of the spout. Along with fan power supply frequency declined, droplet deposition quantity peak areas shifted towards the spout. Meanwhile, the function of wind power transmission weakened, the number of deposition peak areas and the distances between the adjacent deposition peak areas were becoming small. It was found in spray breadth tests (44.5–49.5 Hz) that deposition quantity on sampling points which were distributed within ±2 m of the tube axis reached up to 97.11% of total deposition quantity in sampling areas. The far away deviated from the axis, the little droplet quantity deposited. The results demonstrate that air-assisted spraying can possess fine directivity and prevent droplet drift, and the features will not change with frequency variation. The droplet deposition beyond 8m of the spout is affected obviously by natural wind. In actual spraying operation, power supply frequency can be regulated, according to the distance between the sprayer and target, to keep the droplet to deposit mostly in the target area and thus increase the utilization of pesticides. The spraying effect can be improved by weakening the height differences between the nozzle positions.