Abstract:

Due of pepper harvested by pepper harvester contains high rate of impurity， the effect of wind sorting is poor. In order to reduce the pepper impurity rate and improve the pepper air selection’s effect， a pepper wind-separation device was designed. Using the coupled research method of computational fluid dynamics （CFD） and discrete element method （DEM）， the separation process of pepper wind sorting was simulated， the separation mechanism and motion state of the pepper mixture in the flow field were analyzed， and the effect of wind speed on pepper wind sorting was discussed. The results of the simulation showed that the average impurity rate of pepper was 11.774%， 4.624% and 1.676% at wind speeds of 15， 20 and 25 m·s^-1， respectively， and the loss rate of pepper was 0.959%， 1.798% and 6.476%， respectively. The above results showed that the wind speed had a great influence on the wind sorting effect of pepper， when the simulated wind speed was increased to 20 m·s^-1， the average rate of impurity of pepper decreased by 7.15% and the average loss rate increased by 0.839% compared to that at 15 m·s^-1 wind speed； when the simulated airflow speed of wind sorting was adjusted to 25 m·s^-1， the average impurity rate of pepper in the cleaning process decreased by 2.948% and the average loss rate increased by 4.678% compared with the airflow speed of 20 m·s^-1. Combining the impurity content and loss rate of pepper air sorting， it can be seen from the comparative analysis that when the wind speed was 20 m·s^-1， the sorting effect was better， with the pepper impurity rate of 4.624% and the pepper loss rate of 1.798%. The results provided reference for the designing and optimization of the wind sorting device of the pepper harvester.

Key words: pepper cleaning, wind sorting device, DEM-CFD coupling, separation mechanism, simulation studies

摘要：

辣椒收获机收获的辣椒由于含杂率高导致风选效果差，为降低辣椒含杂率，设计了辣椒风选分离装置。采用计算流体力学（computational fluid dynamics，CFD）和离散元法（discrete element method，DEM）耦合研究方法，模拟了辣椒风选分离过程，分析了流场中的辣椒混合物分离机理和运动状态，并讨论了风速对辣椒风选的影响。仿真结果表明，在风速为15、20及25 m·s^-1时，辣椒含杂率分别为11.774%、4.624%、1.676%，辣椒损失率分别为0.959%、1.798%、6.476%。上述结果表明：风速对辣椒的风选效果影响很大，当模拟风速提高到20 m·s^-1时，辣椒平均含杂率较15 m·s^-1风速时下降了7.15%，平均损失率上升了0.839%；而当仿真的风选气流速度调整为25 m·s^-1时，清选过程中辣椒平均含杂率较气流速度20 m·s^-1时辣椒的平均含杂率降低了2.948%，平均损失率上升了4.678%。综合辣椒风选的含杂率及损失率，在风速为20 m·s^-1，风选效果较好，此时辣椒含杂率为4.624%，辣椒损失率为1.798%。研究结果可为辣椒收获机的风选分离装置设计及优化提供参考。

关键词: 辣椒清选, 风选装置, DEM-CFD耦合, 分离机理, 仿真研究