本文選題：沉積分布　切入點：霧滴軌跡　出處：《中國農(nóng)業(yè)大學》2016年博士論文　論文類型：學位論文

【摘要】：在溫室環(huán)境中用氣流輔助方式噴施農(nóng)藥時,霧滴在氣流脅迫下的飛行軌跡與附著行為受到氣流速度場、壓力場、霧滴物理性質(zhì)(如粒徑、初始速度等)、噴霧角度及靶標具體參數(shù)(如形狀、大小、位置等)等條件的影響。本文主要探討在溫室環(huán)境中用氣流輔助方式噴施農(nóng)藥時,施藥對象(靶標)周圍的流場對霧滴飛行軌跡及霧滴附著行為所產(chǎn)生的影響。本文使用數(shù)值模擬研究霧滴速度、霧滴粒徑以及噴霧角度對霧滴沉積率的影響,并通過試驗手段驗證了模擬結果的可靠性。計算域為長1600mm,寬720mm,高1000mm的空間。為便于建模,將植株簡化為高于地面400mm距離左邊界840mm的120mmx 120mmx30mm的長方體靶標。通過本文的工作,我們可以得到以下結論：1)以霧滴粒徑為50μm,噴霧角度為60°的流場分析霧滴的沉積條件。在靶標附近區(qū)域,對區(qū)域內(nèi)的霧滴軌跡進行分析后發(fā)現(xiàn),霧滴在3個方向?qū)崿F(xiàn)附著的最大可能時間必須同時滿足x方向的最大可能運行時間和y方向的最大可能運行時間均大于z方向的運行時間,才能實現(xiàn)對靶標的附著;2)粒子粒徑分別設置為10μm、30μm、40μm、50μm、60μm、70μm、80μm和100μm,噴霧角度分別設置為75°、60°、45°、30°和15°,計算不同條件下粒子附著靶標的沉積率。增大粒徑與增大噴霧角度都有助于獲得較高的霧滴的沉積率,但是當霧滴粒徑較小時,增大噴霧角度并不能獲得明顯的沉積率增加的效果。而當霧滴粒徑較大時,增大噴霧角度會顯著增加霧滴的沉積率；3)噴霧角度設置為75°、60°、45°、30°和15°,對比40μm與80μm粒徑霧滴的運動軌跡。霧滴沉積與否與流場中的壓力分布以及霧滴初始位置有關。在同樣的壓力場條件下,霧滴粒徑大的更容易沉積。因為在靶標上表面的高壓區(qū)對空氣存在加速作用,推動靶標上表面的空氣流向靶標邊緣,粒徑較大的霧滴的隨流性較差,對空氣的加速過程不敏感,所以能夠?qū)崿F(xiàn)沉積;4)噴霧角度設置為75°45°和150。噴霧過程中靶標下方存在霧滴不能到達的遮擋區(qū)域,靶標對霧滴運動的遮擋長度與噴霧角度有關。在噴霧角度小于45°時,靶標的遮擋長度受噴霧角度的影響較大,其大小隨著角度的增加而增大。而當噴霧角度大于45°時,靶標的遮擋長度受噴霧角度的影響較小;5)噴霧角度設置為60°,氣流速度則選取0.5m/s到3.0 m/s之間且間隔為0.25 m/s的11個速度條件來研究各進口速度條件下靶標對霧滴沉積的影響。當采用不同噴霧速度時,霧滴在靶標上表面的沉積率受到靶標附近的壓力場及速度場的影響很大。當霧滴粒徑為50μm,噴霧角度為60°時,隨著噴霧速度的增加,霧滴的沉積率下降。
[Abstract]:When pesticide was sprayed in greenhouse by airflow aid, the flight path and adhesion behavior of droplets under airflow stress were subjected to airflow velocity field, pressure field, droplet physical properties (such as particle size, etc.). The effects of initial velocity, spray angle and target parameters (such as shape, size, position, etc.) are discussed in this paper. The effect of the flow field around the target on the droplet flight path and the droplet adhesion behavior was studied in this paper. The effects of droplet velocity, droplet diameter and spray angle on droplet deposition rate were studied by numerical simulation. The reliability of the simulation results is verified by experimental means. The calculation field is 1600mm in length, 720mm in width and 1000mm in height. In order to model the model, the plantlet is simplified as a cuboid target of 120mm x 120mmx30mm above the left boundary of 400mm above the ground. We can get the following conclusion: 1) the deposition conditions of droplets are analyzed in the flow field of 50 渭 m droplet size and 60 擄spray angle. In the area near the target, the droplet trajectories in the region are analyzed. The maximum possible time for fog droplets to achieve attachment in three directions must satisfy both the maximum possible running time in the x direction and the maximum possible running time in the y direction, which is larger than that in the z direction. The particle size was set to 10 渭 m, 30 渭 m, 40 渭 m, 50 渭 m, 60 渭 m, 70 渭 m, 80 渭 m and 100 渭 m, respectively, and the spray angle was set at 75 擄, 60 擄, 45 擄, 30 擄, and 15 擄, respectively. The deposition rate of particles attached to the target was calculated under different conditions. Increasing the particle size and increasing the spray angle were helpful to obtain the results. Higher deposition rate of droplets, However, when the droplet size is small, the effect of increasing spray angle is not obvious, but when the droplet size is larger, When the spray angle was increased, the deposition rate of droplets was significantly increased. The spray angles were set to 75 擄60 擄45 擄C 30 擄and 15 擄, comparing the motion trajectories of 40 渭 m and 80 渭 m size droplets. The deposition of droplets was related to the pressure distribution in the flow field and the initial position of droplets. Under the same pressure field, Because the high-pressure area on the surface of the target accelerates the air, and promotes the air on the surface of the target to flow to the edge of the target, the larger droplet has a poor flowability and is insensitive to the acceleration process of the air. So it can be realized that the spray angle is set to 75 擄45 擄and 150 擄. During the spray process, there is an unreachable occlusion area under the target, and the length of the fog droplet motion is related to the spray angle. When the spray angle is less than 45 擄, The occlusion length of the target is greatly affected by the spray angle, and its size increases with the increase of the angle, but when the spray angle is greater than 45 擄, The occlusion length of the target is less affected by the spray angle.) the spray angle is set to 60 擄, and the airflow velocity is determined by 11 velocity conditions between 0.5 and 3.0 m / s, with an interval of 0.25 m / s, to study the droplet deposition of the target at each inlet velocity. When different spray rates are used, The deposition rate of droplets on the surface of the target is greatly affected by the pressure field and velocity field near the target. When the droplet size is 50 渭 m and the spray angle is 60 擄, the deposition rate decreases with the increase of spray velocity.
【學位授予單位】：中國農(nóng)業(yè)大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：S491

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本文編號：1628862