基于CFD的氧化沟中推流器转速与分布特性

针对目前氧化沟流速过低,污泥沉积的现象,根据秦皇岛污水处理厂氧化沟的三维图纸,建立三维推流器模型并进行非结构化四面体网格划分.基于Navier-Stokes方程和标准k-ε湍流模型,采用SIMPLE算法对氧化沟进行数值模拟,计算出各转速下推流器的功率、氧化沟各个截面的速度分布、速度死区占比以及旋涡个数.结果表明:当推流器功率能达到氧化沟所需能量且不超过电动机额定功率时可得到推流器最优转速;氧化沟池型结构不变的情况下,改变推流器安装位置,能有效改善氧化沟流速分布,减少污泥沉积;针对入口处的旋涡问题,可以通过改变入流角度来加以改善.为实际工程中推流器的转速和布置选择提供了理论依据.

Study on characteristics of rotational speed and installation position of submerged propellers in oxidation ditch by CFD

At present,oxidation ditches in wastewater treatment plants are associated with problems such as too low fluid velocity and sludge deposition.A three-dimensional oxidation ditch model with submerged propellers was built based on the existing drawing of the oxidation ditch in the Qinhuangdao Wastewater Treatment Plant and the fluid domains were meshed with unstructured-tetrahedral cells.Based on the Navier-Stokes equations and the standard k-εturbulence model,the SIMPLE algorithm was used to simulate water flows in the oxidation ditch.The power of the propellers and velocity distribution in several cross-sections were calculated at different rotational speeds.Also,the dead water zone ratio and number of vortices were analysed.The results show that the optimal rotational speed of the propellers can be decided under the condition that the power of two propellers can provide the mechanical energy required by the oxidation ditch without exceeding the motor rated power.When the pool structure remains unchanged,altering submerged propeller installation position can improve fluid velocity distribution and reduce sludge deposition in the oxidation ditch effectively.For the vortex at the entrance,it can be improved by changing the inflow angle.The study outcomes in the paper have provided theoretical guidance for propeller rotational speed selection and installation position determination.