混凝过程流场形态表征与絮体形成机制研究

The dominant position of the fluid motion in the efficient flocculation reactors in waterworks is usually turbulent vortex flow. But at present, the control indexes and parameters of the design and operation used to control the reactors are deduced on the basis of laminar flow, which are used for turbulence flocculation. It is difficult to explain in theory, but also, it can restrict the further improvement of the existing flocculation technology. The formation mechanism of flocs formed in the flocculation process has close relationship with the physiochemical conditions and the environment of hydrodynamics in the flocculation basin. That is to say, the research on the dynamics of turbulence is closely related with the study of the morphological characteristics of flocs. An experiment plan as the main method will be submitted, several sets of different specifications of Taylor -Couette reactors will be used to produce the different scales of vortices and simulate the turbulent vortex flow of the actual flocculation tank, with rotational Reynolds number, Re, as the control condition. The flow field of flocculation process in the Taylor -Couette reactors will be measured by particle image velocimetry (PIV). At the same time, the characteristics of the microscopic morphology variation and motion informations of floc particles in flocculation flow field will be acquired synchronously. Then with the help of advanced analysis software, the response and the correlation between flocculation effect and the morphological characteristics, the flocs formation mechanism of turbulence vortex flow will be obtained. Finally, the flocculation mechanism of vortex and the essence of dynamics of turbulent vortex flow should be revealed.

水厂高效絮凝构筑物中占主导地位的流体运动一般为湍流涡流动，但目前用于控制反应池设计运行的控制指标多是从层流的基础上推导得出的，用于紊流絮凝，除了在理论上难以解释，也会限制对现有絮凝工艺的进一步改进。 絮凝过程中絮体形成机制与絮凝池内物化条件和水动力学环境关系密切，所以，对湍流絮凝动力学的研究与对絮体颗粒形态特征的研究密切相关。课题组计划以实验为主要研究手段，应用多组规格不同的Taylor-Couette反应器，以旋转雷诺数Re为控制条件，制造产生不同尺度的涡旋，人工模拟实际絮凝池中的各种湍流涡流场，采用粒子成像速度场仪(PIV) 对Taylor-Couette反应器内的混凝过程进行流场测量，同时，同步获取絮体颗粒在混凝流场中的微观形貌变化特征及运动信息，再借助先进的计算分析软件，得到湍流涡流场中流场形态特征、絮体形成机制与絮凝效果之间的响应与关联关系，揭示涡絮凝机制及其动力学本质。

采用粒子成像速度场仪（PIV）对Taylor-Couette涡流场进行测量，获得各转速下涡流场信息。基于PIV测量结果，应用Fluent计算流体力学软件(CFD)对Taylor-Couette涡流场进行数值模拟，从多个层面上验证同等条件下的涡流场形态以及其所对应的转速区间的划分范围，用不同视角寻找涡流场形态特征与涡流动机制（可用旋转雷诺数Re或内筒转速n反映）间的区别与联系，对涡的形态特征及其转速分区进行研究与确认。同时应用不同几何规格的Taylor-Couette反应器在不同水力条件、不同化学条件下进行各种混凝试验，再用PIV测量混凝过程，对各种流态下的速度场及絮体颗粒在环隙流场中的聚集过程进行在线监测，获取不同混凝剂与水中颗粒物在相同或不同的涡流场作用下形成的絮体的特征。对综合了化学条件和水动力学条件的混凝过程进行全方位的同步测量与表征，定量分析反应器内涡流场形态特征、絮体产生机制及特征等因素与混凝效果之间的关联关系。研究以旋转雷诺数为前提和基础，并将其转换为内筒转速进行涡流场控制；有目的地制造出可重现的、不同形态的涡流场。通过重复各种混凝剂在不同水力条件下的混凝过程，对混凝过程中絮体在涡流场中的发展变化过程进行了反复测量研究，将混凝过程中水力条件特征、化学条件特征、生成絮体的运动特征以及絮体形貌特征在同一实验空间中进行表征。借助混凝过程中的流场特征、浊度去除率、形成絮体的形貌变化等信息，考察流场水动力学因素对混凝效果的影响，研究不同形态涡流场中的混凝动力学机理，为传统涡絮凝理论与高效絮凝反应体系之间存在的矛盾寻找一种解决办法，以弥补传统涡絮凝理论的不足。