气固两相流场中残膜-土壤-棉杆团聚体筛分过程解析及筛分机构优化研究

Aiming at the difficult problem of separation of residual film and soil and cotton pole after mechanized recovery. The research group put forward the separation scheme of the synergizing effect of "airflow cleaning and cylinder screening"，and the roller screen type film hybrid air-selecting mechanism was developed. However, there is a problem of unstable screening performance. Aiming at solving this problem, this project centers on the movement pattern and separation mechanism of aggregates of residual film, soils, and straw in the air-solid two-phase flow field of the air-and-screen cleaning device, adopts the theoretical analysis, simulation, and experimental research methods, and studies the following aspects: (1) Analyzes the spatial distribution pattern of the air flow field and impact of each factor on the air flow field distribution; (2) Analyzes the movement change pattern of particle groups in the air-solid two-phase flow field, studies the interaction between particles, and particles and screen surface during the screening process, and establishes the corresponding mathematical model.Explores particle group quality changes during the screening and spatial distribution pattern after the screening; (3)Builds the air-and-screen cleaning device and control test system for which parameters are adjustable, conducts the orthogonal test, uses the response surface analysis methodology, and research on the change pattern of impacts of the cleaning device structure and work parameters on the residual film separation rate. The expected research result is going to reveal the movement and separation mechanism of aggregates of residual film, soils, and straw in the air-solid two-phase flow field and prove the internal correlation between external factors and the residual film separation rate in the field. The research result will effectively solve the separation problem, improve the recycling and reuse rate of residual film, and facilitate sustainable development of agriculture.

针对机械化回收后的残膜与土壤、棉杆不易分离的难题，课题组提出“气流清选+滚筒筛分”协同作用的新方法，试制了滚筒筛式膜杂风选机构，但目前存在筛分性能不稳定的问题。基于此，本项目以残膜-土壤-棉杆团聚体为研究对象，围绕其在气固两相流场中运动规律、筛分机理这一科学问题，采用理论分析、数值计算和试验研究相结合的方法，重点研究：（1）筛分过程中气流场空间分布及变化规律。（2）残膜-土壤-棉杆团聚体在气固两相流场中滑塌、瀑泻和离心的姿态运移变化规律，以及筛分过程中团聚体内部相互碰撞、团聚体与筛面碰撞等，建立相应的运动学和动力学模型。（3）气固两相流场内、外在因素与筛分性能间的内在关联机制，优化设计滚筒筛式膜杂风选机构。预期研究成果将探明残膜-土壤-棉杆团聚体在气固两相流场中的运动及筛分机理，获取提升筛分性能稳定性的控制策略。研究结果将有效解决膜杂分离难题，对提升残膜再利用水平及农业可持续发展意义重大。

机械化回收后的残膜中含有大量棉杆、土壤等杂质，由于没有高效的残膜筛分设备，回收后的膜杂混合物只能被随意堆放、掩埋或者焚烧，对环境造成了二次污染。针对这一问题，项目组基于膜杂混合物空气动力学特性的不同，提出“气流清选+滚筒筛分”协同作用的新思路，试制了滚筒筛式膜杂风选机构。. （1）以滚筒筛转速、喂料口风速和滚筒筛长度为试验因素，以分离后残膜的含杂率为试验指标进行实地试验，结果表明各因素对残膜含杂率的影响由大到小为：滚筒筛转速＞滚筒筛长度＞喂料口风速。通过正交试验极差分析和方差分析得出，当滚筒筛转速为30r/min，喂料口风速为6.15m/s，滚筒筛长度为2800mm时，分离后残膜含杂率为8.4%。研究结果可为膜杂分离设备研发提供理论依据。. （2）对圆筒筛内膜杂混合物进行运动分析，选取圆筒筛转速、进风管风速、气流角度为试验因素，以膜中含杂率和杂中含膜率作为评价指标，，分析各因素对膜杂分离作业性能的影响。结果表明，各因素对膜中含杂率影响主次顺序依次为: 进风管风速、圆筒筛转速、气流角度; 各因素对杂中含膜率影响主次顺序依次为: 圆筒筛转速、进风管风速、气流角度。利用Design-Expert 软件响应曲面图，进行了综合影响效应分析，得出当圆筒筛转速为23. 8 r/min、进风管风速为5. 9 m/s、气流角度为2. 7° 时，膜中含杂率为10. 60%，杂中含膜率为0. 133%。对上述优化结果进行试验验证，得出在该参数组合下的膜中含杂率平均值为10. 54%，杂中含膜率平均值为0. 132%。研究结果极大的提升了气力式圆筒筛膜杂分离机的筛分性能。. （3）针对CMJD-1500 型残膜捡拾打包机在黄河三角洲地区推广作业时因捡拾、打包装置作业参数调整不当而导致残膜捡拾率、压包成型率较低的问题，采用六因素三水平Box-Behnken 试验设计原理，建立了关键参数与残膜捡拾率、压包成型率之间的数学模型，确定了样机较优的作业参数组合，为黄河三角洲地区残膜捡拾打包装备的研发提供参考。