茶树叶片表面喷雾液滴斜撞击行为研究
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国家重点研发计划项目(2018YFD0600202)


Oblique Impact Behavior of Spray Droplets on Tea Tree Leaves Surface
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    摘要:

    在喷雾场景中,茶树叶片具有不同倾斜方向,且会受到不同方向喷雾液滴的撞击。为掌握液滴斜撞击茶树叶片时的撞击行为及影响机理,提出了利用椭圆铺展面积来衡量斜撞击时液滴的铺展变化,并推导出包含叶片倾角和撞击角的斜撞击液滴铺展及反弹数学预测模型。为验证理论准确性,利用两台高速摄像机对喷雾液滴撞击茶树叶片的撞击过程及结果进行测试和分析。研究结果表明,撞击角、初始直径、撞击速度对粘附液滴的铺展面积影响由大到小为撞击速度、初始直径、撞击角,其中初始直径及撞击速度对液滴铺展面积有显著性影响,且是极强正相关。对于细、中液滴,撞击角对铺展面积无显著性影响;对于粗大液滴,撞击角有显著性影响,建议采用90°撞击角。茶树叶片表面具有亲水性,水滴撞击叶片表面时无反弹行为,此结果与反弹预测模型结果吻合。对液滴飞溅的影响程度由大到小为初始直径、撞击速度、撞击角。初始直径及撞击速度对液滴飞溅有显著性影响,液滴初始直径和撞击速度越大,越容易发生飞溅,撞击角对液滴飞溅无显著性影响。因茶树叶片表面比较光滑,无长绒毛,表面粗糙度较小,飞溅临界值Kcrit采用108.4较合适。

    Abstract:

    In the spray scene, the tea tree leaves have different tilt directions which are subjected to impact by different directions of spray droplets. In order to grasp the impact behavior and influence mechanism of the droplet impact on the tea tree leaves, the elliptical spreading area was used to measure the spreading variation of the droplet during the oblique impact, and a new type of oblique impact droplet spreading and rebound mathematical prediction model, including blade inclination angle and impact angle was derived. In order to verify the theoretical accuracy, two highspeed cameras were used to test and analyze the impact process and results of spray droplets striking tea leaves.The results showed that the impact angle, initial diameter and impact velocity on the spreading area of the adherent droplets were the impact velocity, initial diameter and impact angle. The initial diameter and impact velocity had a significant effect on the droplet spread area, and were highly positively correlated. For fine and medium droplets, the impact angle had no significant effect on the spreading area; for coarse droplets, the impact angle had a significant effect, and 90° impact angle was recommended. The surface of the tea tree leaves was hydrophilic, and there was no rebound behavior when the water droplets hit the surface of the leaf. The result was consistent with the rebound prediction model. The degree of influence on the droplet splatter was the initial diameter, the impact velocity, and the impact angle. The initial diameter and impact velocity had a significant effect on droplet splatter. The larger the initial diameter and impact velocity of the droplet were, the more likely it was to splash. The impact angle had no significant effect on droplet splatter. Because the surface of tea leaves was relatively smooth, no long fluff, and the surface roughness was small, the splash threshold Kcrit was suitable to be 108.4.

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刘冬梅,周宏平,郑加强,茹煜.茶树叶片表面喷雾液滴斜撞击行为研究[J].农业机械学报,2019,50(5):96-103,195. LIU Dongmei, ZHOU Hongping, ZHENG Jiaqiang, RU Yu. Oblique Impact Behavior of Spray Droplets on Tea Tree Leaves Surface[J]. Transactions of the Chinese Society for Agricultural Machinery,2019,50(5):96-103,195.

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  • 收稿日期:2019-03-21
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  • 在线发布日期: 2019-05-10
  • 出版日期: 2019-05-10