变速搅拌混沌混合的PIV试验研究

针对搅拌槽内部的流体混合在湍流状态不成问题，但当流体处于层流状态下如何提高混合效率的实际问题，为提高层流状态下搅拌槽内流体的混合效率，采用混沌混合使叶轮以变转速做周期性运动。利用粒子图像测速技术对层流搅拌槽变速混沌混合流场进行试验研究，对所测得的粒子图像采用相应图像处理软件处理，得到了六个不同角度处流体径向速度分布云图，并对比分析变速搅拌与常速搅拌混合流场速度分布曲线的不同。试验结果表明，叶轮变转速运动时，搅拌槽内径向速度范围宽，扰动区域大，说明变转速运动比常转速运动的搅拌混合效果好、搅拌效率高。所做研究对充分认识变速层流搅拌诱发混沌混合的机理，为大型层流混沌混合搅拌槽的设计提供指导性建议，具有重要理论意义及实际应用价值。

PIV EXPERIMENTAL INVESTIGATION OF CHAOTIC MIXING USING NON-CONSTANT SPEED STIRRING

There is no problem for mixing inside the stirred tank when the flow is in turbulent state. However, how to improve the mixing efficiency becomes a practical problem while the flow inside stirred tank is in laminar condition. For the pur- pose of enhancing the mixing efficiency inside laminar stirred tank, chaotic mixing is applied with the impeller rotating in periodic form. The particle image velocimetry technique is used to measure the laminar flow field inside the stirred tank, the particle images acquired are post-processed by special image processing software, radial velocity distributions at six different angles are displayed in the form of flood contours. The results velocity curves of mixing with variable rotation speed are compared with that of mixing with constant rotation speed. The experimental study shows that the area disturbed by radial velocity with variable rotating speed is larger than that with constant rotating speed, and proves that the mixing effect and the mixing efficiency are better with the axis rotating with variable speed. The research work is significant for analyzing the mechanism of chaotic mixing and for designing of large scale stirred tank.