气粒并流向上流动中准静止颗粒团现象

为研究不同操作条件下气粒并流向上两相流动中颗粒团的特性,采用流动显示的方法对颗粒团的瞬态运动行为进行观察,采用图像灰度梯度法对颗粒团进行识别,根据颗粒团图像的面积计算颗粒团截面尺寸,采用互相关方法计算颗粒团瞬时速度,并根据相关系数的变化判断颗粒团变形和计算颗粒团生存时间。结果表明:在某种操作条件下,竖直窄槽道壁面附近会出现类似“沙丘”形状的大尺度准静止颗粒团;这种颗粒团的形状和尺寸能在较长时间内基本保持不变,其运动速度在零附近波动;准静止颗粒团的生存时间可达1~2 s,而其他类型颗粒团的生存时间不会超过0.25 s。

Quasi-stationary clusters in cocurrent upward gas-solid flows

The characteristics of clusters in cocurrent upward gas-solid flows were observed using flow visualization for various operating conditions to study the instant behavior of the clusters.The clusters were identified by gray scales with the size determined by the number of pixels in the cluster image.The cluster velocities were calculated by correlating cluster positions in successive pictures with the correlation coefficient also used to judge the cluster deformation and to calculate the cluster lifetime.Large dune-shaped quasi-stationary clusters appear near the wall with the sizes and shapes of these clusters almost constant and their velocity fluctuations near zero.The lifetimes of these quasi-stationary clusters are 12 s,while the lifetimes of other clusters away from the wall are less than 0.25 s.