膜生物反应器内流场动力学特性的PIV实验研究

浸没式膜生物反应器系统内膜面附近的气液两相流动力学特性对控制浓差极化和膜污染具有重要影响。应用粒子图像测速(PIV)技术对浸没式膜生物反应器内近膜面的液相流场动力学特性进行了研究。采用相分离技术灰度分辨法将通过PIV技术得到的气液两相流场图像中的液相速度场进行辨别,得到膜面附近的液相流场数据,并应用Tecplot软件计算得出液相流的涡量特性。在3 mm曝气孔径,2.5、3.0、3.5、4.5、5.5和6.5 m3/h 6种曝气强度下分析了膜面附近的液相速度场和涡量场。结果表明,曝气强度对液相流场和涡量场的影响较大,在一定范围内增加曝气强度可以使得液相速度和涡量增加,同时,分析了3 mm孔径下圆帽状气泡的动力学特性。研究结果为膜生物反应器系统的优化设计提供了研究经验和实验数据。

Research on dynamics characteristics of flow field in MBR by PIV technology

The dynamic characteristic of gas-liquid two phase flow around membrane fibers have important effects on controlling concentration polarization and membrane pollution in submerged membrane bioreactor system. Particle image velocimetry (PIV) technology was used to measure the dynamic characteristic of liquid phase flow around membrane fibers. First, the gas-liquid two phase flow field image was gained by PIV technology, gray resolution method was developed and implemented to discriminate liquid phase velocity field from two phase flow field image, and vorticity field data of liquid flow was calculated around membrane fibers by Tecplot. We analyzed the liquid phase flow field and calculated vorticity field data around membrane fibers under the condition of aeration intensity of 2.5,3.0,3.5,4.5,5.5 and 6.5 m³/h in bore diameter of 3 mm.It was shown that aeration intensity affected liquid phase flow field and vorticity field greatly, increasing aeration intensity in a certain range can make the liquid velocity and vorticity increase. Under the experimental conditions, the optimal aeration intensity identified as 6.5 m³/h. At the same time, we also analyzed dynamics characteristics of bubble with bore diameter of 3 mm. The study provides experimental data and research experience for optimization design of membrane bio-reactor (MBR).