基于DEM-CFD耦合的辣椒清选仿真研究

doi:10.13304/j.nykjdb.2022.0008

摘要/Abstract

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

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

中图分类号:

S225.92

张德俊, 张小明, 吴荻, 林蜀云, 张太华, 徐卫平. 基于DEM-CFD耦合的辣椒清选仿真研究[J]. 中国农业科技导报, 2023, 25(7): 87-96.

Dejun ZHANG, Xiaoming ZHANG, Di WU, Shuyun LIN, Taihua ZHANG, Weiping XU. Simulation of Pepper Cleaning Based on DEM-CFD Coupling[J]. Journal of Agricultural Science and Technology, 2023, 25(7): 87-96.

图/表 15

图1 风选装置注：1—出口Ⅰ；2—进风口；3—进料口；4—清选室；5—出口Ⅲ；6—出口Ⅱ。

Fig. 1 Wind-sorting deviceNote：1—Outlet Ⅰ；2—Air inlet；3—Feed inlet；4—Cleaning room；5—Outlet Ⅲ；6—Outlet Ⅱ.

图2 风选装置网格

Fig. 2 Grid of wind sorting device

图3 水平气流中的颗粒受力分析

Fig. 3 Force analysis of particles in horizontal airflow

图4 风选颗粒阻风效应简化原理注：1为前端连续运动的粒子组；2为后端连续运动的粒子组。

Fig. 4 Simplified principle of wind-selected particle wind-blocking effectNote： 1 is particles group of continuous motion at the front segment； 2 is particles group of continuous motion at the end segment.

图5 DEM-CFD耦合流程图

Fig. 5 Flow chart of DEM-CFD coupling

表1 材料的物理参数

Table 1 Physical parameters of the material

材料 Material	辣椒 pepper	辣椒叶 pepper leaf	辣椒茎秆 pepper stick	钢 Steel
泊松比 Poisson ratio	0.34	0.28	0.41	0.29
剪切模量 Modulus of shear/ $P a$	2.51e6	1.02e6	1.27e6	7.99e10
密度 Density/（kg/ $m 3$ ）	790.89	598.95	1 074.43	7 860.00

表1 材料的物理参数

Table 1 Physical parameters of the material

材料 Material	辣椒 pepper	辣椒叶 pepper leaf	辣椒茎秆 pepper stick	钢 Steel
泊松比 Poisson ratio	0.34	0.28	0.41	0.29
剪切模量 Modulus of shear/ $P a$	2.51e6	1.02e6	1.27e6	7.99e10
密度 Density/（kg/ $m 3$ ）	790.89	598.95	1 074.43	7 860.00

表2 相关颗粒的材料接触系数

Table 2 Material contact coefficient of related particles

材料 Material	恢复系数 Recovery coefficient	静摩擦系数 Coefficient of static friction	滑动摩擦系数 Coefficient of sliding friction
辣椒-辣椒 pepper-pepper	0.410 0	0.53	0.46
辣椒-辣椒叶 pepper-pepper leaves	0.250 0	0.43	0.35
辣椒-辣椒茎秆 pepper-pepper sticks	0.360 0	0.49	0.42
辣椒-钢 pepper-Steel	0.430 0	0.56	0.31
辣椒叶-辣椒叶 pepper leaves-pepper leaves	0.000 2	0.86	0.82
辣椒叶-辣椒茎秆 pepper leaves-pepper Sticks	0.130 0	0.70	0.59
辣椒叶-钢 pepper leaves-Steel	0.000 6	0.60	0.47
辣椒茎秆-辣椒茎秆 pepper sticks-pepper sticks	0.390 0	0.76	0.67
辣椒茎秆-钢 pepper sticks-Steel	0.370 0	0.54	0.38

图6 辣椒颗粒的运动轨迹注：颗粒迹线红色代表辣椒，绿色代表辣椒叶。

Fig. 6 Schematic diagram of the winnowing of pepper particlesNote：Particle traceRed shows chilli， and green shows chilli leaf.

图7 物料颗粒位置瞬态图（t=1 s）

Fig. 7 Transient diagram of material particle position （t=1 s）

图8 风速20 m·s-1的辣椒含杂率

Fig. 8 Impurity rate in pepper with wind speed of 20 m·s-1

图9 风速20 m·s-1的辣椒损失率

Fig. 9 Pepper loss rate at wind speed 20 m·s-1

图10 不同风速下的辣椒颗粒分布

Fig. 10 Distribution of pepper particles at different wind speeds

图11 不同风速下的辣椒含杂率

Fig. 11 Impurity rate of pepper at different wind speeds

图12 不同风速下的辣椒损失率

Fig. 12 Loss rate of pepper at different wind speeds

表3 不同风速的仿真结果

Table 3 Simulation results at different wind speeds

风速 Wind speed/（m·s^-1）	含杂率最大值 Maximum impurity rate/%	平均含杂率 Average impurity rate/%	平均损失率 Average loss rate/%
15	22.234	11.774	0.959
20	8.713	4.624	1.798
25	3.554	1.676	6.476

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