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基于CFD-DEM的機采鮮葉管道集葉過程數(shù)值模擬研究
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浙江省重點研發(fā)計劃項目(2021C02028)


Numerical Simulation of Leaf Gathering Process of Fresh Leaf Collecting Pipeline Based on CFD-DEM
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    摘要:

    為揭示乘坐式采茶機的集葉管道內(nèi)部氣流特性,利用計算流體力學(CFD)和離散單元法(DEM)對管道內(nèi)氣固兩相流動進行數(shù)值模擬。通過多球面聚合法建立機采鮮葉數(shù)值計算模型,在分析鮮葉顆粒運動規(guī)律基礎上,分別對其不同進口風速、鮮葉顆粒尺寸、彎管結(jié)構(gòu)進行模擬分析。研究結(jié)果表明,數(shù)值模型可預測集葉管道的集葉效果以及最佳風速;在最佳進口風速范圍內(nèi),鮮葉顆粒越大,管道內(nèi)的剩余顆粒越多,容易產(chǎn)生沉積;鮮葉顆粒流在穿過豎直管道到彎管時形成一束彎管流曲線,且彎管結(jié)構(gòu)對鮮葉顆粒運動有一定影響,流場平均速度呈先降低后升高的變化規(guī)律。選用一個彎管半徑為0.04m圓角彎管作為集葉彎管結(jié)構(gòu),同時減少橫向管道長度,選擇內(nèi)側(cè)長度為0.03m豎直管,避免鮮葉顆粒由重力作用導致的沉積,保證集葉順暢性。數(shù)學模型仿真與試驗結(jié)果表明:減少橫直管長度,采用圓角彎管與適合的豎直管長度的集葉管道,穿透率不小于86.8%,滿足集葉要求。本文提出的鮮葉顆粒建模方法,用于集葉管道與鮮葉流相互作用的離散元仿真分析及管道結(jié)構(gòu)優(yōu)化。該研究可為集葉管道其他工作參數(shù)優(yōu)化提供參考。

    Abstract:

    In order to reveal the airflow characteristics in the leaf collecting pipe of a riding tea picker, the gas-solid two-phase flow in the pipe was numerically simulated by computational fluid dynamics (CFD) and discrete element method (DEM). The numerical calculation model of machine-picked fresh leaves was established by the multi-sphere polymerization method. On the basis of analyzing the movement law of fresh leaf particles, the different changes of inlet wind speed, fresh leaf particle size and bend structure were simulated and analyzed respectively. Through the numerical model the blade collecting effect and the optimal wind speed and feeding quantity of the riser pipe could be predicted. In the optimal inlet wind speed range, the larger the fresh leaf particles were, the more residual particles were in the pipeline, which was easy to produce deposition. Fresh leaf particle flow formed a bend curve when it passed through the vertical pipe to the bend. The bend structure had a certain influence on the movement of fresh leaf particles. The average velocity of flow field was decreased firstly and then increased. A rounded elbow with a radius of 0.04m was selected as the blade collector elbow structure, and the transverse pipe length was reduced. The inner length was 0.03m to avoid deposition caused by gravity action of fresh leaf particles and ensure the smoothness of blade collector. Through mathematical model simulation and experimental results, it was verified that the blade collecting pipe with rounded corner bend can meet the requirements of blade collecting by reducing the length of horizontal and straight pipe. The pipe with round corner elbow structure had a penetration rate of more than 86.8%. The fresh blade particle modeling method proposed was used for discrete element simulation analysis and structural optimization of the interaction between the leaf collecting pipe and the fresh blade flow. The research results provided a theoretical basis for the optimization of optimization design of the fresh leaf collecting pipeline.

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翁曉星,陳長卿,王剛,韋真博,江麗,胡新榮.基于CFD-DEM的機采鮮葉管道集葉過程數(shù)值模擬研究[J].農(nóng)業(yè)機械學報,2022,53(11):424-432. WENG Xiaoxing, CHEN Changqin, WANG Gang, WEI Zhenbo, JIANG Li, HU Xinrong. Numerical Simulation of Leaf Gathering Process of Fresh Leaf Collecting Pipeline Based on CFD-DEM[J]. Transactions of the Chinese Society for Agricultural Machinery,2022,53(11):424-432.

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  • 收稿日期:2022-07-29
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  • 在線發(fā)布日期: 2022-11-10
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