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對沖噴頭噴霧場液滴分布特性試驗
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國家林業(yè)局948項目(2015-4-56)和安徽高校自然科學研究重點項目(KJ2018A0543)


Experiment on Droplet Distribution Characteristics in Spray Field of Impinging Nozzle
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    摘要:

    植保扇形噴頭的噴霧扇形面內(nèi)不同位置處液滴直徑是不相同的,呈現(xiàn)接近于U形分布的中間液滴直徑小而兩側液滴直徑偏大的情況,這導致同高度水平方向上各點處的液滴在靶標上的沉積行為不同,致使防治效果存在差異。本文對出水口孔徑1mm和切槽角30°的對沖噴頭噴霧場的液滴直徑分布特性進行試驗,該噴頭是基于射流和撞擊流耦合作用的新型噴頭,發(fā)現(xiàn)對沖噴頭在噴霧扇形面內(nèi)的液滴直徑呈現(xiàn)中間區(qū)域液滴直徑較大且均勻而兩側液滴直徑較小的特性,如噴施壓力0.4MPa時在300mm高度測試面上,噴霧扇形面內(nèi)中間區(qū)域液滴直徑在265~268μm,而靠近兩側邊緣處的液滴直徑在250~252μm,這有利于解決噴桿式噴霧機大田作業(yè)時液滴直徑分布不均勻的不足;并對噴頭這一特性進行理論分析,提出在分裂區(qū)的3次霧化(即擾動霧化、撞擊霧化和振蕩霧化)是引起這一特性的根本原因。同時采用徑向不均勻指數(shù)對噴霧場的液滴分布均勻特性進行定量表征分析,發(fā)現(xiàn)徑向不均勻指數(shù)能夠總體反映噴霧場的非均勻特性,當噴施壓力在0.6~0.7MPa范圍時,徑向不均勻指數(shù)在0.47~0.51較小范圍內(nèi)變化,說明在該壓力范圍內(nèi)工作時噴頭噴霧場具有良好的液滴均勻分布特性。

    Abstract:

    The droplet sizes are different at different positions in the spray field of flat-fan nozzle which are widely used in agriculture. It shows like the U-shaped distribution, that is, the droplet diameters of the middle droplet are smaller and the droplet diameters of both sides are larger, which results in the differences of the droplet depositional behavior on the targets at different points of the same height in the horizontal direction, leading to different control effects. The droplet sizes of the impinging nozzle were obtained according to the test system for atomizing performance of nozzles. Experiments were conducted on droplet distribution characteristics in spray field of the impinging nozzle with the exit diameter of 1mm and the groove angle of 30°. The nozzle was a new nozzle based on the coupling of jet and impinging jets. It was found that the droplet diameters of the middle droplet were uniform and the droplet diameters of both sides were smaller. For instance, when the spraying pressure was 0.4MPa, the droplet diameters of the middle droplet were 265~268μm and the droplet diameters of both sides were 250~252μm on the test surface at height of 300mm. The new nozzle was beneficial to solve the insufficiency of uneven droplet size distribution of boom sprayers in field operation. The characteristics of the new nozzle were analyzed theoretically and the three times of atomization (disturbance, impact and oscillating) in the cracking-zone was considered as the fundamental cause of these characteristics. Meanwhile, the droplet distribution uniformity of spray field was quantified by the radial nonuniformity index (RNI). It proved that the radial nonuniformity index can reflect the overall non-uniformity of spray field. The value of radial nonuniformity index was varied in a small range (0.47~0.51) when the pressure was in the range of 0.6~0.7MPa, showing that the spray field of the impinging nozzle had good droplet uniform distribution. The impinging nozzle provided a beneficial technological support for the development of intelligent precision spraying machine for plant protection.

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董福龍,周宏平,茹煜,施明宏,陳青,易克傳.對沖噴頭噴霧場液滴分布特性試驗[J].農(nóng)業(yè)機械學報,2018,49(12):116-121,128. DONG Fulong, ZHOU Hongping, RU Yu, SHI Minghong, CHEN Qing, YI Kechuan. Experiment on Droplet Distribution Characteristics in Spray Field of Impinging Nozzle[J]. Transactions of the Chinese Society for Agricultural Machinery,2018,49(12):116-121,128.

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  • 收稿日期:2018-07-24
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  • 在線發(fā)布日期: 2018-12-10
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