Intensification of chaotic mixing in a stirred tank with a punched rigid-flexible impeller and a chaotic motor

摘要

Graphical abstractTwo doughnut rings have been formed above and below the rigid impeller with a normal motor. These regions remained segregated from the rest of the mixing system, and acid penetrated the segregated regions due to the diffusive mechanisms, not the convective flow mechanisms, to neutralize the base. The presence of the segregated regions would extent the mixing time. The punched rigid-flexible impeller coupled with a chaotic motor was more effective to eliminate segregated regions. Because punched rigid-flexible impeller could generate a series of high-speed jet flows in the rotation process, and co-reverse rotation of chaotic motor could generate aperiodic flows.Display OmittedHighlights?Segregated regions were observed through visualization experiment.?Largest Lyapunov exponent was used to characterize chaotic characteristics.?Laminar mixing intensification was achieved by punched rigid-flexible impeller.?The co-reverse mixing was much more efficient than normal mixing.AbstractLaminar mixing of non-Newtonian CMC solution was investigated experimentally in a stirred tank with a rigid impeller, a rigid impeller coupled with a chaotic motor, a rigid-flexible impeller, a rigid-flexible impeller coupled with a chaotic motor, a punched rigid-flexible impeller, and a punched rigid-flexible impeller coupled with a chaotic motor. Visualization experiment was used to reveal the presence of segregated regions, and observe the structure changes of segregated regions. The mixing performance was characterized by the largest Lyapunov exponent (LLE) and dimensionless mixing time (NTm). Results showed that punched rigid-flexible impeller could further enhance the value of LLE, namely, the chaotic extent of mixing system compared with rigid impeller and rigid-flexible impeller, and theNTmfor punched rigid-flexible impeller was shorter than that for rigid impeller and rigid-flexible impeller at the same consumption per unit volume (Pv). The chaotic motor could further increase LLE value, and reduce theNTmon the basis of the normal motor. Moreover, the optimum aperture diameter and aperture ratio of punched rigid-flexible impeller were 8mm and 12%, respectively, and the variable speed period of 10s and constant speed period of 5s of chaotic motor were particularly suitable for the laminar mixing process.