基于Fluent的棉花烘房流场均匀性优化

Optimization of flow field uniformity in cotton drying room based on Fluent

目前已研发的热泵热风干燥系统中的气流上升式烘房在实际干燥中,存在内部不同位置农产品干燥不均、干燥品质差的问题,影响产品的后续储存。基于此,结合标准湍流模型与多孔介质模型建立气流上升式热泵烘房的CFD(计算流动力学)模型并验证模型可靠性。分别探讨原始烘房空载与满载状态下的气流分布状态,针对烘房内部结构,创新性地提出不同角度导流叶片与不同变方孔径匀风板的9种组合优化方案,在各项速度指标与均匀性指标对比分析下确定最优方案,并分析最优方案下的满载优化效果。结果表明:在进风口处设置15°导流叶片及内部使用B类变方孔径匀风板的优化组合为最优方案,此方案下满载时烘干区物料层范围内XZ不同位置平面的平均速度由0.087 m/s增强至0.2 m/s,平均相对标准偏差由44.8%降至25.1%,平均均匀性系数由0.84提升至0.91;烘干区物料层范围内XY不同高度平面的平均速度由0.096 m/s增强至0.23 m/s,平均相对标准偏差由30.1%降至24.32%,平均均匀性系数由0.88提升至0.94。本研究可为气流上升式热泵烘房的结构改进提供理论方法与技术参考。

The air flow rising drying room in the heat pump hot air drying system which has been developed at present had the problems of uneven drying and poor drying quality of agricultural products in different internal positions,which affected the subsequent storage of products.Based on this,combined with the standard turbulence model and porous medium model,this paper established the CFD model of the air flow rising heat pump drying room,verified the reliability of the model,discussed the air flow distribution state of the original drying room under no-load and full load respectively,and innovatively proposed nine combined optimization schemes of guide wind vanes with different angles and uniform air plates with different variable square apertures according to the internal structure of the drying room.Under the comparative analysis of various speed indexes and uniformity indexes,the optimal scheme was determined,and the full load optimization effect with the optimal scheme was analyzed.The result showed that the optimal combination of setting a 15°guide vane at the air inlet and using a B-type variable square aperture uniform air plate was the optimal solution.Under this scheme,the combination effect of 15°guide wind vane and class B uniform wind plate was the best,at full load,the average velocity of XZ at different positions within the material layer in the drying area increased from 0.087 m/s to 0.2 m/s,the average relative standard deviation decreased from 44.8%to 25.1%,and the average uniformity coefficient increased from 0.84 to 0.91;the average velocity of XY planes at different heights within the material layer of the drying area increased from 0.096 m/s to 0.23 m/s,the average relative standard deviation decreased from 30.1%to 24.32%,and the average uniformity coefficient increased from 0.88 to 0.94.This study can provide theoretical method and technical reference for the structural improvement of air flow rising heat pump drying room.