生物倍增反应器气泡流态特性分析

PIV measurement and POD analysis of bubble flow characteristics in bio-doubling reactor

利用激光粒子图像测速技术(PIV)对生物倍增反应器在7种不同进水流量下的气泡流态特性进行了测量和分析,利用特征正交分解方法对所测2个截面的气泡流场进行分解,提取流场中含能大尺度结构。结果表明,进水流量的增加导致了气泡轴向速度减小,径向速度增大,气泡附壁效应增强;不同进水流量对气泡的扰流影响程度不同,气泡流态的速度场和涡量面积分布存在差异,在特定工况下气泡流场产生了涡旋。上部区域进水流量为0时,1阶模态占能比例最高,约为7.2%;下部区域进水流量为0.18 m^3/h时,1阶模态占能比例最高,约为4.5%。低阶特征模态中存在明显的大尺度结构,且大尺度的流动结构与液相混合行为间接相关。当进水流量为0.90 m^3/h时,2个截面的涡量面积分布最均匀,气泡死区最少,此时气泡流态最佳。在本试验条件下,进水流量为0.90 m^3/h时,反应器整体气泡流态最佳。

The characteristics of bubble flow in gas-liquid two phase flow in the bio-doubling reactor under seven different inlet flow rates were investigated by using particle image velocimetry（ PIV） technology. The bubble flow field in the two cross-sections of the reactor was decomposed further using proper orthogonal decomposition analysis for extracting the large scale structure of the flow. The analysis results show that the axial velocity decreases,the radial velocity increases and the Coanda effect is enhanced with the increase of the influent flow rate. As the influences of different inflow discharges on the bubble flow are different,so that there are differences between the velocity field and vorticity distribution of the bubble flow,and the vortex occurs in the bubble flow field and the bubble flow field produces vortex flow under a specific working condition. When the inflow discharge in the upper region（ A） is 0,the highest energy content of the first order modes is about 7. 2% of the total kinetic energy,and when the inflow discharge in the lower area（ B） is 0. 18 m^3/h,the highest energy content of the first order modes is about 4. 5% of the total kinetic energy. The proportion of the first order mode is not quite different in the A and B regions. There are obvious large scale structures in the low order characteristic modes,and the large scale flow structure is indirectly related to the liquid mixing behavior. When the inflow discharge is 0. 90 m^3/h,the area of two cross sections of the reactor is the most uniform and the gas phase dead zone is the least,and at this time,the flow regime is the best. Under such experimental conditions,when the inflow discharge is 0. 90 m^3/h,the overall bubble flow regime of the reactor is the best.