搅拌叶片与氧化沟流场流固耦合分析及在曝气机优化设计上的应用

Aiming at the existing problem such as velocity distribution is not ideal, the oxygenation efficiency is low, the dissolved oxygen content is not easy to control in oxidation ditch, and the contradiction between the oxygenation, plug flow and energy consumption existence in working aerators. Start from the flow characteristics of the oxidation ditch, the research on fluid-structure interactions of mixing blade and the flow will be been made, which based on the hydraulic jump theory and oxygen transfer theory and the shear mixing theory, to study the mixing, plug flow and oxygenation mechanism of the aeration machine. Starting from changing the mixing blade profile and floating installation method, by changing the aeration machine blade parameters to change the sewage circulation mode, a new idea in turn to guide the optimization design of aerator was proposed. In this study, the theory of gel-inert body, mixing theory based on "load-off when encounter”, and friction theory of coating blade were established. And more, through the establishment of the rheological models and dynamic equations of aerators to promote the oxidation ditch flow system, the relationship between the oxygen transfer efficiency, building, energy consumption, sludge gel particle diffusion rate and aeration machine blade geometric parameters (shape, diameter, bending angle) and motion parameters (power, speed, immersion depth) was established. To enhance the ability of mixture elevate, to increase the sludge settling velocity, and increasing oxygen exposure area as the target to optimize and design the mixing blades, which provide theoretical basis for the optimization design of the aeration machine and for the improving of the oxidation ditch process.

针对氧化沟存在的流速分布不理想，充氧效率低，溶氧量不易控制的难点及曝气机工作中存在的充氧、推流与能耗之间的矛盾。本项目从研究氧化沟流场特性入手，研究搅拌叶片与流场的流固耦合作用，运用多相流理论、剪切搅拌理论和氧传质理论研究曝气机的搅拌、推流及充氧机理，提出从改变叶片型线、结构和安装方式入手，通过改变曝气机叶片参数来改变污水循环模式，反过来指导优化设计曝气机的新思路。研究提出了凝胶惰性体剪切理论，逢正抽心搅拌理论以及被覆叶片的摩阻理论。通过研究曝气机推流下的氧化沟流场的流变学模型和动力学方程，建立氧总转移效率、能耗、污泥凝胶粒子扩散速率与曝气机叶片几何参数（线型、直径、弯曲角）及运动参数（功率、转速、浸深等）之间的关系，以提高混合液提升能力，增大氧传质效率，减少能耗和减小污泥剩余率为指标优化设计叶片，揭示氧化沟流场特性与叶片参数之间的关系，为曝气机的优化设计和氧化沟的工艺改进提供理论依据。

倒伞曝气机具有良好的充氧效率和推流能力，在污水处理的氧化沟工艺中应用最为广泛。研究基于“逢正抽芯”理论，提出了一种以对数螺旋线为母线，翼型型面作为截面的新型曝气机叶片，并针对该曝气机叶片进行了仿真模拟和优化设计。利用优化设计理论和CFD流体仿真确定了不同实验环境（转速，浸没深度）和不同结构参数（叶片数，叶片倾斜角度）下曝气机标准充氧能力的变化规律。研究进一步用叶片数、叶片角度、叶片的开口大小这三种实验参数作为自变量，以氧总转移系数为因变量开展实验研究，分别搭建了圆形氧化沟和卡鲁塞尔氧化沟试验台上，分别使用3D打印技术制作了不同参数的搅拌叶片和生产加工了叶片的实验模型，对两种流场下的充氧动力效率进行了实验研究，特别是使用了高速摄像技术，拍摄曝气机运转时水体中产生气泡的形态大小与分布情况，并在实验研究的基础上，结合CFD-PBM模拟分析的结果，对曝气机叶片的结构进行了改进和优化。