大悬浮轻颗粒固液两相流中的有序结构

应用三维颗粒图像跟踪技术,对竖直管内向上大悬浮轻颗粒固液两相流中分散相即颗粒相瞬时分布进行非接触测量,由此对顺流方向颗粒串组成的有序相分布结构进行观察研究。实验发现,当液体流动速度大于某一确定值时会有明显的颗粒串出现,此时颗粒由于受液体速度梯度诱导的强升力作用而紧贴管壁运动;随着液体流动速度的降低,颗粒串逐渐消失而颗粒沿管径向的分布会向着管中心方向发展;当液流速度进一步降低,颗粒开始在水平方向团聚。分析表明液体流动的剪切作用是颗粒串生成和稳定的机制。实验还显示,随着颗粒相平均份额的增加,流动中串间颗粒的相互作用加强,颗粒分布结构也随之受到影响。

ORDERED STRUCTURE IN LARGE AND LIGHT PARTICLE-LIQUID TWO PHASE FLOWS

With a three-dimensional particle image tracking technique (PIT), the instantaneous distribution of particles was non-intrusively measured in upwards large and light expanded polystyrene-liquid two phase flows in a vertical pipe. The ordered structure which was composed of particle clusters aligning in the flow direction was observed and studied. When the liquid velocity was higher than a transition velocity, particle clusters would appear, and particles would be tightly close to the pipe wall due to the strong lift force caused by liquid velocity gradient. On the other hand, particle clusters disappeared by degrees and particles were distributed closer to the pipe center with the decrease of liquid velocity. When liquid velocity was lower, particles became conglomerate horizontally. The result shows that liquid shear is the mechanism of the formation and stabilization of particle clusters. The experiment also indicated that the particle distribution structure was affected when the interaction of particles between adjacent clusters became stronger with the increase of average particle phase fraction.