高密度循环流化床中气固两相流动结构的一维成像分析

ONE - DIMENSIONAL IMAGE ANALYSIS OF GAS AND SOLID FLOW STRUCTURE IN HIGH DENSITY CIRCULATING FLUIDIZED BED

本文利用新的测试方法即一维成像系统在较宽的操作条件下对高密度循环流化床中气固两相流动的瞬态结构进行了研究,得到大视场下快速床内两相流瞬时结构图像,并通过对图像进行统计和相关分析,得到了颗粒团在床内的特性参数:出现概率、径向大小,轴向渡越时间沿径向的分布及这些分布随床内操作参数的变化规律。研究结果表明,影响颗粒团特性参数的主要因素是局部时均颗粒浓度和操作气速。

Instantaneous images of gas - solid flow structure in High Density Circulating Fluidized Bed (HDCFB) are presented by means of a one -dimensional optical -fiber image analytic system specially developed for this experiment. The research is carried out in a circulating fluidized bed 9 m in height and 186 mm in ID. The operating conditions are in the range ug:0-8. 0 m/s, Gs:18-180 kg/(m2 · s) and bed voidage: 0. 65-0. 99. The distributions of the cluster characteristics along the radial direction,such as the probability of the cluster appearance, the radial cluster size, and the axial cluster interception time, are obtained through the statistics and correlation analysis of the cluter images. It is shown that the cluster characteristics are mainly affected by bed density and gas velocity. When gas velocity and solid flux are kept constant, radial cluster size, axial cluster interception time and the probability of cluster appearance decrease along the bed height, i. e. ,they decrease with decreasing bed density. When bed density is kept constant, all the above three cluster parameters decrease with increasing gas velocity.