基于CFD的氧化沟推流器能量配置计算

Determining installation position and number of submerged propellers in oxidation ditch by CFD

针对目前污水处理厂氧化沟运行能耗过大和推流器布置不合理等问题,根据推流器木模图,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.计算了不同设计工况下推流器的功率与氧化沟各个截面的速度大小及分布,同时对液流在推流器作用下的流动情况进行了研究.模拟结果表明:在不改变推流器安装参数的前提下,通过改变推流器的安装位置,可以有效避免弯道处推动力太大产生的返混现象.除此以外,因推动力衰减过多导致过弯道时流速太低、底部容易积泥的问题也得到了解决.通过适当调整推流器的数目,确定了混合推动所需要的最小功率密度,在能够满足氧化沟流速需求前提下,同时达到了推流器能量消耗最小的目的.该研究可为氧化沟推流器能量配置计算提供理论指导.

The problems,such as too high energy consumption for oxidation ditch operation and how to decide submerged propellers installation position,exist in sewage treatment plants currently,thus the flow in an oxidation ditch was simulated based on the Navier-Stokes equations,standard-turbulence model and SIMPLE algorithm.The three-dimensional submerged propeller model was built by the exi-sting blade pattern drawing,and the fluid domains were meshed with unstructured tetrahedral cells.The shaft power of submerged propeller and the velocity distribution in various cross-sections of the oxidation ditch were estimated under different working conditions;meanwhile,the flow field driven by the propeller was investigated as well.The results indicate that on the premise of the submerged propeller installation parameters unchanged,altering the installation position of submerged propeller can avoid the back mixing phenomenon caused from a too strong driving force.Besides,the sludge deposition problem,which is caused from too low flow velocity resulted by too much attenuation of the driving power in the bends,also can be solved.By properly adjusting the number of submerged propellers,a minimum power density can be determined to meet the driving force needed for mixing.Thus not only the velocity in the oxidation ditch has met the requirement,but also the minimum energy consumption has been achieved.The study can provide a theoretical guidance for determining the installation position and number of submerged propellers.