Abstract:In order to research on the effect of different spraying modes of fan nozzle on spatial deposition of droplet, droplet size measurement test device and deposition distribution test device were established by using NJS-1 wind tunnel for plant protection. The droplet size measurement test device was mainly composed of spray system, laser particle size analyzer and so on. The nozzle was mounted on the vertical reciprocating guide rail with the moving speed of 6.7cm/s and the horizontal distance between the nozzle and the laser beam was 30cm. During the tests, the spray pressure was firstly stabilized, and then the laser particle size analyzer was turned on. In order to sample the entire spray stoke area, the spraying nozzle was controlled by a singlechip microcomputer to move at a certain speed. Droplet deposition distribution test device was mainly composed of spray system, wind tunnel system, acquisition system and so on. During the tests, the flow rate of the spray nozzle was controlled by an electronic timer to open/close the solenoid valve to ensure that the spray time of each test was fixed at 10s. The fluorescent tracer BSF was selected as the spray medium and was mixed with water at the ratio of 0.30g/L. After each spray test, the collection line was placed in the plastic bag with 30mL deionized water for full oscillation washing, the amount of fluorescent agent content was determined by the calibrated fluorescence analyzer for each test eluent. The LURMARK-04F80 standard fan nozzle was used in the dropsize distribution and deposition performance tests. The effects of spray pressure and wind speed on droplet size and the influence of wind speed, spray pressure, spray orientation and nozzle direction on droplet deposition were investigated. Three calculation models were employed to compare different influence factors of droplet drift reduction percentage. The results of droplet size distribution experiments showed that at the same wind speed, the increase of spray pressure would cause the decrease of DV0.1, DV0.5 and DV0.9 and the increase of ΦVol＜100μm, but minor changes of droplet spectrum width S; under the same spray pressure, the increase of wind speed would cause the increase of DV0.1 and DV0.5 but minor change of DV0.9, the decrease of ΦVol＜100μm and droplet spectrum width S was from 1.44 to 1.17. The results of droplet deposition distribution tests showed that when spray pressure was increased from 0.2MPa to 0.4MPa, in the plane parallel to spray direction，the droplet deposition was increased at 2~3m from the spray nozzle，droplet deposition was decreased when spray pressure was increased far away from the nozzle, in the plane vertical to spray direction, the droplet deposition was increased at 0.1~0.2m from the ground and increased when spray pressure was increased, in the middle position, the droplet deposition was decreased when spray pressure was increased, the droplet deposition was close to zero at the height nearest to the nozzle. When wind speed was increased from 1m/s to 5m/s, the droplet deposition was increased on both planes parallel and vertical to spray direction; when the nozzle direction was changed from -15° to 15°, the droplet deposition was increased on both planes parallel and vertical to spray direction; when the nozzle direction was changed from 0° to 30°, the droplet deposition was decreased with the increase of nozzle direction on both planes parallel and vertical to spray direction with minor difference. Compared with the reference spray, the values of DPRP obtained from three calculation models showed that spray pressure, wind speed and spray orientation greatly influenced the droplet drift reduction percentage, especially the crosswind speed. This study can provide experimental data guidance for the selection of spray parameters for spray operation in the field.
