基于CFD-DEM的机采鲜叶管道集叶过程数值模拟研究
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浙江省重点研发计划项目(2021C02028)


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

    为揭示乘坐式采茶机的集叶管道内部气流特性,利用计算流体力学(CFD)和离散单元法(DEM)对管道内气固两相流动进行数值模拟。通过多球面聚合法建立机采鲜叶数值计算模型,在分析鲜叶颗粒运动规律基础上,分别对其不同进口风速、鲜叶颗粒尺寸、弯管结构进行模拟分析。研究结果表明,数值模型可预测集叶管道的集叶效果以及最佳风速;在最佳进口风速范围内,鲜叶颗粒越大,管道内的剩余颗粒越多,容易产生沉积;鲜叶颗粒流在穿过竖直管道到弯管时形成一束弯管流曲线,且弯管结构对鲜叶颗粒运动有一定影响,流场平均速度呈先降低后升高的变化规律。选用一个弯管半径为0.04m圆角弯管作为集叶弯管结构,同时减少横向管道长度,选择内侧长度为0.03m竖直管,避免鲜叶颗粒由重力作用导致的沉积,保证集叶顺畅性。数学模型仿真与试验结果表明:减少横直管长度,采用圆角弯管与适合的竖直管长度的集叶管道,穿透率不小于86.8%,满足集叶要求。本文提出的鲜叶颗粒建模方法,用于集叶管道与鲜叶流相互作用的离散元仿真分析及管道结构优化。该研究可为集叶管道其他工作参数优化提供参考。

    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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翁晓星,陈长卿,王刚,韦真博,江丽,胡新荣.基于CFD-DEM的机采鲜叶管道集叶过程数值模拟研究[J].农业机械学报,2022,53(11):424-432.

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  • 收稿日期:2022-07-29
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  • 在线发布日期: 2022-11-10
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