混凝过程中絮体形貌的PIV成像观测与表征

采用粒子成像速度场仪(PIV)对Taylor-Couette反应器内的混凝过程中絮体的微观形貌进行了观测与表征.结果表明,内筒转速在20～60r/min范围内,生成的絮体颗粒较大,粒径分布均匀,絮凝沉淀效果最好.由于内筒旋转速度的变化直接导致混凝流场形态的变化,所以混凝过程中流场形态的变化对絮体生长过程有重要影响,进而直接影响到混凝效果.混凝过程中流场的周期性变化、涡间存在液体传递的波状涡结构有利于絮体颗粒的结合生长,并导致较高的絮凝沉淀去除率.这也说明PIV技术能够在测量流场的同时较好地反映混凝过程中微絮体的形貌变化特征,从而实现对絮凝过程的原位观测与表征.

Characterization and measurement of the flocs during the coagulation process by PIV

Particle image velocimetry (PIV) was applied to characterize and measure the morphological changes of the flocs during the coagulation process. The results indicated that the flocs particles were much bigger, their size distribution was more uniform, and the sedimentation efficiencies were higher when the rotation speed of the inner cylinder was in the range 20~60r/min. The rotation speed of the inner cylinder had a great influence on the flow field which directly affected the flocs size, morphology and coagulation efficiencies. The vortex flow field structure change with time periodically and the bulk fluid motion may be beneficial for the flocs to combine with each other and grow up, leading to the higher flocculation efficiency. This research demonstrated that the morphology of the flocs in the coagulation process can be characterized and described perfectly by PIV and PIV can be exploited as a useful tool in the in-situ observation and measurement during coagulation processes.