Authors

Abstract

Airborne dust generated during straw pickup can impair operating visibility and local air quality; however, the respective contributions of mechanical particle detachment and aerodynamic entrainment in flail-type pickup headers remain insufficiently quantified. This study combined discrete element method (DEM) and computational fluid dynamics (CFD) analyses with field measurements to investigate these two processes. A bonded corn root stubble–soil DEM model was established in EDEM, and the bond fracture rate was used to characterize the relative degree of particle detachment. The effects of ground clearance (30–90 mm), rotor speed (4100–5300 rpm), forward speed (0.5–1.5 m/s), plant spacing (200–300 mm), and row spacing (300–500 mm) were evaluated. CFD simulations were then used to characterize the time-averaged airflow field within the pickup-header housing. Increasing the ground clearance from 30 to 90 mm reduced the bond fracture rate by 44.5%, whereas increasing the rotor speed from 4100 to 5300 rpm increased it by 52.3%. By relating the DEM particle-detachment states to the CFD flow-field characteristics, three dust-generation pathways were identified: stubble fragmentation, root extraction, and direct entrainment of loose surface particles. Rotor speed affected both mechanical detachment and airflow entrainment at the header inlet. Field measurements showed that the selected low-dust operating condition, with a ground clearance of 75 mm, rotor speed of 4400 rpm, and forward speed of 0.75 m/s, reduced total suspended particulate (TSP), PM10, and PM2.5 concentrations by 62.2%, 58.4%, and 53.8%, respectively, compared with the dust-intensive condition. By linking particle detachment, airflow entrainment, and field measurements within a mechanism-based framework, this study clarifies the effects of operating parameters on dust generation and provides a basis for selecting low-dust operating parameters and improving pickup-header inlet design.

Abstract in Chinese

锤爪式秸秆捡拾作业产生的扬尘会降低作业视野并加剧局部空气污染，但其机械扰动与气流卷吸机制尚缺乏定量认识。本文采用相互独立的离散元法(DEM)和计算流体动力学(CFD)分析，并结合田间试验开展验证。基于EDEM构建玉米根茬—土壤粘结颗粒模型，以粘结键断裂率表征颗粒从根茬—土壤基体中的脱离程度，考察离地高度(30～90 mm)、锤爪转速(4100～5300 r/min)、前进速度(0.5～1.5 m/s)、株距(200～300 mm)和行距(300～500 mm)的影响；利用Fluent分析捡拾割台壳体内部时均流场及其颗粒卷吸作用。结果表明，在本研究设定的参数范围内，离地高度和锤爪转速引起的粘结键断裂率变化幅度最大。离地高度由30 mm增至90 mm时，粘结键断裂率降低44.5%；锤爪转速由4100 r/min增至5300 r/min时，粘结键断裂率提高52.3%。扬尘可归纳为根茬破碎飞溅、根茬拔除牵引和土壤表层松散颗粒直接卷扬三条产生途径，且提高锤爪转速会同时增强机械脱离和入口气流卷吸。田间试验表明，离地高度75 mm、锤爪转速4400 r/min和前进速度0.75 m/s的低尘工况，相较高扬尘工况可使TSP、PM10和PM2.5浓度分别降低62.2%、58.4%和53.8%。研究结果可为锤爪式秸秆捡拾割台的低尘作业参数配置及入口结构改进提供依据.