液固循环流化床中的颗粒速度场

PARTICLE VELOCITY FIELD IN LIQUID-SOLID CIRCULATING FLUIDIZED BEDS

利用超声多普勒测速仪 (UDV)对液固循环流化床中颗粒流场进行了系统的实验研究 .实验测定了不同轴向位置处的颗粒速度分布 ,得到了较完整的颗粒速度场 ,分析了入口区对流场分布的影响 ,考察了表观液速和颗粒循环速率等操作条件对颗粒速度场分布特点的影响 。

Ultrasound Doppler velocimeter(UDV) is used to investigate particle velocity field in a liquid-solid circulating fluidized bed. Radial deviation index is used to scale radial non-uniformity of particle velocity. It is found that particle flow structure shows considerable radial non-uniformity, namely core-annulus flow. At certain axial positions, central particle velocity increases with the increase of superficial liquid velocity and particle circulation rate. In the developed region, central particle velocity and radial non-uniformity of flow structure decrease along the axial position. Radial non-uniformity of particle velocity increases with the increase of superficial liquid velocity and particle circulating rate at certain axial positions. In the entrance region, radial non-uniformity is larger than that of the developed region and central particle velocity is less than that at the beginning of the developed region because of particle acceleration. The influence of the entrance region increases with the increase of superficial liquid velocity.