组合桨液相搅拌槽内流动特性的实验研究及数值模拟

采用粒子图像测速技术 (PIV)，对直径为0.19 m的三层组合桨 (HEDT+2WH) 搅拌槽 (直径为0.48 m) 内的流场进行了实验研究，并利用标准 k-ε 模型对相应的流动特性进行了数值模拟。实验结果表明：通过改变层间距、顶层桨的浸没深度及上两层桨的操作方式可以得到4种不同流型，每种流型内循环结构的数目各不相同；上两层桨下压式操作时，流场的循环结构最少，只有两个；高速区和高能量区的分布相同，都位于各个桨叶的射流区内，且底桨射流区内的速度值和湍流动能值都大于上两层桨。模拟结果表明：标准 k-ε 模型对流场的预测较为准确，但对于有5个循环结构的流型模拟误差较大；湍流动能分布型式的模拟值与PIV实验结果吻合较好，但数值偏低，表明标准 k-ε 模型在预测复杂流型时需要改进；功率准数的模拟值与实验值基本一致。

Experimental study and numerical simulation of fluid flow in a liquid multiple impeller stirred tank

The flow characteristics in a stirred tank of diameter 0.48 m agitated by a triple impeller (HEDT + 2WH) of diameter 0.19 m have been experimentally investigated by particle image velocimetry (PIV) and numerically simulated by computational fluid dynamics (CFD) using the standard k-ε model. The PIV results showed that four flow patterns were obtained by changing the impeller spacing and the operation mode of the top two impellers. The number of circulation loops was different for each flow pattern. Only two circulation loops were found in the flow field of HEDT+2WH_D. A High velocity region and high turbulent kinetic energy region existed in the jet flow of each impeller. The velocity and turbulent kinetic energy in the jet flow of the bottom impeller were larger than those of the top two impellers. The CFD results showed that the flow field predicted by the standard k-ε model is in agreement with PIV data except for the flow pattern with five circulation loops. Although the distribution pattern of turbulent kinetic energy estimated by CFD is consistent with the PIV results, the value is underestimated. The power number predicted by the standard k-ε model is in agreement with the experimental data.