【作者】 陶雷；

【导师】 曾爱军；

【作者基本信息】 中国农业大学 ， 农业机械化工程， 2004， 硕士

【摘要】 机械式罩盖喷雾是一种结构简单、价格便宜和减少雾滴飘失效果好的喷雾方法，其中罩盖结构起着关键的作用。目前国外试验研究的罩盖结构中，双圆弧罩盖效果最好。但由于该罩盖的结构特点，其下方产生较大速度的运动气流和罩盖后部产生的涡流以及上旋气流，将直接影响雾滴的飘失。因此，作者提出双圆弧罩盖结构的改进方法，并进行减少雾滴飘失的对比试验研究。 本文采用导流法在双圆弧罩盖上开口，利用Fluent模拟分析和比较罩盖喷雾流场，并模拟该流场下的雾滴运动轨迹来分析雾滴的飘失性，模拟结果表明：结构改进后的罩盖喷雾流场得到改善，其减少雾滴飘失的效果好于原罩盖，更优于常规无罩盖喷雾。 风洞测量流速来比较模拟流场和试验流场的吻合程度。开口罩盖流场由于相对稳定，模拟和试验的测点流速平均相对误差为15％，未开口罩盖流场中由于涡流影响较大，平均相对误差为22.45％；同时验证了结构改进前后罩盖流场的模拟比较结果和试验比较结果的趋势是一致的。 风洞和室内试验比较了结构改进前后的罩盖喷雾减少雾滴飘失的效果，并和常规无罩盖喷雾对比。风洞试验参数：喷雾药液为含1‰BSF的水溶液，风速1.4m／s，风向垂直于喷雾扇面，温度281k～288k，相对湿度RH9％～20％；室内试验参数：喷雾药液为含2‰BSF的水溶液，喷头处风速为3.2m／s，风向平行于喷雾扇面，温度291k～301k，相对湿度RH15％～21.2％％；分别在喷头下风向喷幅外的空中和地面布点收集飘失和飘移沉积的雾滴量，作为评价减少雾滴飘失效果的指标： 试验结果表明：改进后的罩盖喷雾减少雾滴飘失的效果好于双圆弧未开口罩盖喷雾，常规无罩盖喷雾的雾滴飘失量大于开口罩盖喷雾。更多还原

【Abstract】 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.更多还原