Abstract: In order to analyze the effect of the box structure on the flow velocity changes, pressure at the suction port of the picking head, vortex situation inside the box, and pressure difference at the inlet and outlet of the short stick black fungus negative pressure harvester, a 3D model was established for different suction port positions and picking pipe diameters. Based on Fluent software, the internal flow field of the short stick black fungus negative pressure harvester was simulated. According to the trace diagram, the vortex situation inside the collection box was analyzed when the air outlet was at different positions. The pressure cloud images and vector maps of the internal flow field of the equipment were studied to analyze the changes in flow velocity inside the pipeline under different picking pipe diameters, the average flow velocity inside the box and the wind pressure on the picking mouth. In order to verify the reliability of the data, a standard suction test is set up. The experimental conclusion is consistent with the flow field simulation results, verifying the reliability of the numerical simulation of the flow field. The numerical simulation results show that the diameter of the threaded pipe and the height of the air outlet have a significant impact on the internal flow field of the negative pressure harvester. The larger the diameter of the threaded pipe, the greater the pressure drop in the airflow field. And as the inner diameter of the threaded pipe increases, the airflow velocity inside the pipeline decays faster, and the vortex phenomenon inside the box becomes more severe. The position of the air intake will affect the vortex situation inside the box. The closer the air outlet is to the top of the collection box, the weaker the vortex phenomenon. Taking all factors into consideration, the optimal threaded pipe diameter is 58 mm, and the more suitable suction port position is 60 mm from the center of the air outlet to the top of the box.

Key words: black fungus with short rod, harvester, airflow field, numerical simulation, optimal design

摘要： 为分析箱体结构对短棒黑木耳负压采摘机内部流场的流速变化、采摘头吸风口处的压力、箱体内部涡旋情况、进出风口风压压差的影响，建立不同吸风口位置及采摘管直径的3D模型，基于Fluent软件对短棒黑木耳负压采摘机内部流场进行流场模拟。根据迹线图分析收集箱出风口处于不同位置时，箱体内涡旋情况；研究设备内部流场压力云图与矢量图，分析不同采摘管直径下管道内流速变化、箱体内平均流速值与采摘口所受风压情况。为验证数据可靠性，设置标准吸力试验。试验结论与流场模拟结果相符，验证流场数值模拟的可靠性。数值仿真结果表明，螺纹管直径和出风口高度对负压采摘机内部流场影响显著。螺纹管直径越大，气流场压降越大。且随着螺纹管的内径增大，管道内的气流速度衰减越快，箱体内气流涡旋现象越严重。吸风口位置会影响箱体内涡旋情况。出风口离收集箱顶部越近，涡旋现象越弱。综合考虑，较优的螺纹管直径为58 mm，较合适的吸风口位置为出风口圆心距离箱体顶部60 mm。

关键词: 短棒黑木耳, 采收机, 气流场, 数值模拟, 优化设计