收割机提升搅龙中干燥稻谷的CFD-DEM数值模拟

针对联合收割机刚收获的稻谷由于含水率较大而易霉变的问题，提出了利用远红外联合热风将稻谷在收割谷物提升搅龙中直接干燥的方法。设计了红外加热器安装在搅龙中心的内加热和安装在搅龙外筒上的外加热2种方案，采用CFD-DEM耦合方法对稻谷运动、传热传质过程以及搅龙内的流场进行了仿真分析，并采用外筒加热方案试验对仿真结果进行了验证。结果表明：模拟值和试验值变化趋势一致，最大相对误差仅为8.34%，试验和仿真结果基本吻合；在不同搅龙转速、热风温度、热风风速和喂入量条件下，外加热方案脱水速率比内加热方案至少快2.91%，说明外加热方案干燥效果优于内加热方案；谷粒的升温随着搅龙转速、热风速度和喂入量的增大而减小，随着热风温度的增大而增大；谷粒脱水速率随着搅龙转速和喂入量的增大而减小，随着热风温度和热风速度的增大而增大。上述研究结果为联合收割机谷物提升搅龙中集成干燥装置的设计及干燥过程的优化提供了理论依据。

CFD-DEM Simulation of Paddy Drying in Lifting Screw Conveyor of Harvester

In order to prevent the newly harvested paddy from mildewing due to the high moisture content， a method of direct drying paddy in lifting screw conveyor of combine harvester was proposed by combining far infrared and hot air. The internal heating scheme of installing the infrared heater in the center of the screw conveyor and the external heating scheme of setting the infrared heater on the outer of the screw conveyor were designed. The paddy movement， heat and mass transfer process and fluid flow in the screw conveyor were simulated by coupling method of discrete element methodologies （DEM） and computational fluid dynamics （CFD）. The simulation results were verified by the paddy drying experiment of external heating scheme. The results showed that： the variation trends of simulated and experimental values were consistent and the maximum relative error between the simulated and experimental value was 8.34%， which meaned that the simulation method was acceptable； under different conditions of screw conveyor rotate speed， hot air temperature， hot air speed and feed rate， the dehydration rate of the external heating scheme was at least 2.91% faster than those of the internal one， which showed that the drying effect of the external heating scheme was better than that of the internal one； the increasing temperature of the paddy decreased with the increase of the screw conveyor rotate speed， hot air speed and feeding amount， while increased with the increase of the hot air temperature； the paddy dehydration rate decreased with the increase of the screw conveyor rotate speed and feed rate， and increased with the increase of the hot air temperature and hot air speed. Above results provided theoretical basis for the design and optimization of drying paddy in lifting screw conveyor of combine harvester.