| 立式机械冲击式超微粉碎机分级结构的改进设计 |
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| 引用本文： | 武文璇,于贤龙,张宗超,李青,孙庆运,赵峰,贾振超.立式机械冲击式超微粉碎机分级结构的改进设计[J].农业工程学报,2023,39(12):245-253. |
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| 作者姓名： | 武文璇 于贤龙 张宗超 李青 孙庆运 赵峰 贾振超 |
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| 作者单位： | 山东省农业机械科学研究院，济南 250100 |
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| 基金项目： | 国家自然科学基金项目（青年基金）（32201691）；农业农村部黄淮海现代农业装备重点实验室开放课题（NJY2022QN01） |
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| 摘 要： | 针对当前结构立式机械冲击式超微粉碎机加工的成品物料存在粒度分布较宽且有大颗粒夹带的问题，为了提高其立式分级结构分级性能，对分级室内导流罩轴向位置变化、分级叶轮轴向尺寸变化对分级性能的影响进行研究，该研究在现有分级室结构基础上提出了两种改进结构，改进结构一：导流罩上沿与上端盖贴合，阻断导流罩与上端盖间物料流通路径，分级轮轴向尺寸不变；改进结构二：导流罩位置不变，分级轮叶片高度加高，加高后分级轮叶片上沿距离出料口底端部3 mm。对改进前后结构进行分级性能试验，利用CFD软件，采用气-固两相流的数值模拟方法对分级室内流场进行数值模拟，分析不同结构下流场变化规律来解释试验结果。结果表明：相比改进前，两种改进结构都有效避免了大颗粒进入成品物料，从分级粒径、分级效率及分级精度指数三个指标对比得出改进结构二分级效率及分级精度均优于另外两种结构，改进结构一分级得到的产品更细，但分级效率低。该研究结果可为CWFJ型立式机械超微粉碎机分级室流场研究和结构优化提供方法和理论依据。
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| 关 键 词： | 超微粉碎 数值模拟 分级过程 气/固两相流 |
| 收稿时间： | 2023/3/14 0:00:00 |
| 修稿时间： | 2023/4/21 0:00:00 |
Improved design of the classification structure of vertical mechanical impact superfine grinder |
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| WU Wenxuan,YU Xianlong,ZHANG Zongchao,LI Qing,SUN Qingyun,ZHAO Feng,JIA Zhenchao.Improved design of the classification structure of vertical mechanical impact superfine grinder[J].Transactions of the Chinese Society of Agricultural Engineering,2023,39(12):245-253. |
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| Authors: | WU Wenxuan YU Xianlong ZHANG Zongchao LI Qing SUN Qingyun ZHAO Feng JIA Zhenchao |
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| Institution: | Shandong Academy of Agricultural Machinery Sciences, Jinan 250100, China |
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| Abstract: | Mechanical impact superfine grinder is characterized by the wide working condition, high efficiency, and simple operation. The vertical mechanical impact superfine grinder has been commonly used to crush agricultural by-products in recent years. However, the processed material often contains coarse particles with a wide distribution range, due to the current classification chamber structure. The classification performance can also depend mainly on some changes in the vertical position relationship between the current-guide cover and the classification wheel. In this study, two optimization schemes were proposed for the classification chamber using the initial structure, in order to examine the influence of different position relationships on classification performance. Optimized structure 1 involved the current guide that attached to the upper cover, thereby blocking the flow path between them, while maintaining the height of the classification wheel blades. Optimized structure 2 retained the original position of the current-guide cover in consistence with the initial structure, but increased the height of classification wheel blades. Additionally, 3mm was adjusted for the distance between the top edge of the classification wheel blades and the bottom of the discharge port. Firstly, the performance tests were conducted on three classification chamber structures. Secondly, the CFD software and numerical simulation of gas-solid two-phase flow were employed to analyze the flow of fluid within the classification chamber. Finally, the simulation was used to explain the test findings. The following conclusions were also drawn. Optimized structure 1 yielded a more uniform clipping velocity outside of the classification wheel. However, there was a small variation gradient of axial velocity and flow field velocity in the classification chamber. Consequently, the product with the smaller median particle size was obtained in the optimized structure 1, compared with the others. Classification efficiency and accuracy were only changed slightly. The optimized structure 1 resulted in the absence of large particles in the products, due to the blocked flow path in the attachment of the current-guide cover to the upper cover. Meanwhile, the radial velocity decreased gradually from the outer to the inner of the grading wheel in the optimized structure 2. The reverse vortices were generated between the grading wheel blades, leading to a more uniform axial velocity distribution within the grading wheel and a significant variation gradient of axial velocity and flow field velocity within the classification chamber. Consequently, the product with a larger median particle size was yielded, compared with the others, whereas, the classification efficiency and accuracy were enhanced significantly. Moreover, the increasing height of the grading wheel blades impeded the entry of large particles into the finished material. The reason was that the higher tangential velocity outside the grading wheel promoted the material dispersion and the ejection of large particles. In summary, both optimized structures 1 and 2 resulted in the products devoid of large particles. A comparative analysis was performed on the three classification performance indexes, namely product particle size, classification efficiency, and classification accuracy index. Therefore, the optimized structure 2 demonstrated better classification accuracy and efficiency than before, although was yielded a coarser product particle size. Conversely, the optimized structure 1 enabled the production of ultrafine powder with a smaller particle size, although at the cost of lower classification efficiency. The findings can provide a strong reference and theoretical foundation for the flow field investigation and structural optimization of the classification chamber in the CWFJ vertical mechanical superfine grinder. |
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| Keywords: | superfine grinder numerical simulation gas-solid two-phase flow hierarchical process |
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