Theory And Trial Research On The Arc Shield In Reducing Spray Drift

Mechanical shield spray has good effect in reducing spray drift with low cost, simple structure. The structure is the key point. At present, among the researched structures, the double-foil shield is the best one during experiments. Because of its special structure, the high velocity flow under the shield, big vortex and upcast flow behind the shield will affect the spray drift. If these situations could be changed, the drift can be reduced further. So the shield structure was improved to change the flow field, and experiments will be conducted to validate the effect in reducing spray drift.A slot was cut in the back plate of the double-foil shield to improve the flow field with air diversion method. The flow field and droplets trajectory near the shield are simulated in wind tunnel by Fluent software to analyze the wake flow affecting the spray drift. From simulation, the improved shield spray in reducing drift is better than double-foil shield spray and conventional spray in six types of wind velocity.In order to validate the correctness of the simulation, the flow velocity of X vector is measured to compare the flow field between the simulation and the experiment in wind tunnel. The results indicate that the flow field is improved and more stable than the original shield flow field. The tendency between the improved shield and the original shield from simulation is consistent with the tendency from experiments.The experiment in wind tunnel is to collect the drifted droplets with ball collectors in the air and the deposited droplets with filter paper on the ground after the nozzle down the wind. The spray solution is water with 1%0BSF. The captured droplets weight is regarded as evaluating indicator. Experimental constants include: ambient temperature 281-288k, RH 9%~20%, wind velocity 1.4m/s and vertical to the spray fan. Working pressure 4bar, discharge height 0.4m. Nozzle used in all experiments is LU120-015.Also experiment is conducted to evaluate the spray drift affected by the crosswind in the door of our institute. The spray solution is water with 2%oBSF. The evaluating indicator is also the captured droplets weight. The collectors are placed in the air and on the ground out the spray amplitude down the wind. Experimental constants include: ambient temperature 291k~301k, RH 15%~21.2%, wind velocity 3.2m/s at the nozzle position and horizontal to the spray fan, others are same as the fore experiment.The tendency of the two experiments results is consistent with the tendency from simulation. That indicate the improved shield spray is better than the original shield spray in reducing spray drift, and also more better than conventional spray without shield.