氧化沟反应器流体力学特性的数值模拟与实验研究

Numerical simulation and experimental study of hydrodynamic characteristic in the carrousel oxidation ditch reactor

采用CFD数值计算和体视PIV测试相结合的方法研究卡鲁塞尔氧化沟反应器流场特性。探索复杂边界条件下反应器流场的模拟方法,采用体视PIV技术分别测量了反应器直道、弯道处三维全场流速;研究不同位置处纵、横、垂三向的流动结构和沿程分布特点。结果表明,模拟与实验结果较吻合;纵、垂两向的流动分布是决定沟内水力特性的主要因素;横、垂两向的流动是决定污泥沉积位置的主要因数;外沟靠近曝气叶轮直道段的流速分布上大下小,在低速区底部易发生污泥沉积;外沟远离曝气叶轮直道段流速分布上小下大,利于防止泥水分离;弯道段受横比降和横向环流的影响,内侧容易形成低速区或停滞区而发生污泥沉积。

The CFD and the stereoscopic PIV（particle image velocimetry）were combined to investigate hydrodynamic characteristics in the carrousel oxidation ditch reactor. The method to simulate in complex boundary conditions was explored. The stereoscopic PIV（ particle image velocimetry） was applied to measure the 3-dimen- sional whole-flow-field velocities in the straight and flexual channel-sections of carrousel oxidation ditch reactor. Flow structures in different sections were analyzed and the distribution characters of longitudinal, lateral, vertical velocity along the course of the reactor were compared and discussed. The results show that the velocity simulation results agree well with the experimental results. Longitudinal and vertical flows are the determinative factors of hydraulic characteristic in the reactor. The position of sludge sediment primarily depends on lateral and vertical velocity. In the outboard section near the impeller, the flow rate in the surface is larger than that in the bottom, which would lead to sludge sediment in the low speed section. In the outboard section far away from the impeller, the flow rate in surface is smaller than that in the bottom, which would benefit to prevent sludge separate from wastewater. Because of effects of lateral slope and its circulation flow in the flexural section, low speed and/or stagnancy would occur easily in the inboard section with resulting to sludge sediment.