下行床入口段流体力学及混合行为

针对工业快速反应对气固进料混合过程的特殊需求，在内径140mm，高4.7m的并流下行循环流化床中，采用双光路光纤密度测量技术及磷光颗粒示踪技术，对两种不同的气固并流下行床分布器结构的流动及颗粒混合行为进行了研究．分别考察了人口段颗粒浓度径向分布沿轴向的变化规律及颗粒轴径向混合行为．实验结果表明，下行床入口段颗粒浓度随轴向位置的变化可划分为分布器影响区及湍流控制区．分布器结构对入口段颗粒密度分布有较大影响，利用侧向喷嘴并降低入口处颗粒的射流可以获得较好的径向均布效果．侧向喷嘴的分布器结构更有利于颗粒的径向混合．还考察了入口结构对颗粒混合的影响因素，给出了对Pe_a及Pe_r的关联式．

HYDRODYNAMICS AND MIXING BEHAVIOUR IN ENTRANCE OF DOWNER

The radial solids fraction profiles in the entrance of a 140mm id.Downer was studied by means of a duel─beam optical fiber solids density sensor.The effects of entrance structure,solids circulating rate,gas velocity on radial solids fraction profiles were studied.The radial solids fraction profile can be divided into two regions:the distributor effect region and turbulence control region.The entrance structure has a large influence on the solids fraction profile.A phosphorescent tracer method has been used to determine solids residence time distribution in the entrance of downer.The entrance effect reduces axial solids backmixing and enlarges radial solids mixing.The effects of entrance structure,solids circulating rate,gas velocity and solids fraction on axial and radial solids mixing were studied.The entrance structure has a large influence on the radial solids mixing near the entrance region.