%0 Journal Article %A Zuohua LIU %A Wei SUN %A Xia XIONG %A Changyuan TAO %A Yundong WANG %A Fangqin CHENG %T Chaotic mixing performance and mass transfer enhanced by rigid-flexible impeller with pulse jet %D 2020 %R 10.11949/0438-1157.20200303 %J CIESC Journal %P 4632-4641 %V 71 %N 10 %X

Conventional stirred reactors generally use rigid impeller for mechanical stirring, which leads to the easy creation of isolation mixing regions in the reactor and reduces the efficiency of fluid mixing. The use of multi-flow field coupling to induce chaos and promote more fluids into a chaotic state is one of the effective ways to improve fluid mixing efficiency. In this work, the largest Lyapunov exponent(LLE) and multi-scale entropy(MSE) are investigated with the Matlab compile pressure pulsation signals. The effects of duty ratio, paddle type, flexible paddle thickness, paddle height from the bottom and pulsed air jet flow rate on the chaotic mixing of fluids in a stirred reactor under different pulse periods are explored. In addition, the effects of different impeller types, jet types and air jet flow rate on the volume oxygen mass transfer coefficient KLa are compared and analyzed. When T=0.4 s and D=80%, the results show that the LLE of the rigid-flexible RT impeller compared with the rigid RT impeller increases 11.58% and the MSE of the rigid-flexible RT impeller is also larger than that of rigid RT impeller. It was showed that the pulsed jet rigid-flexible impeller system can better enhance fluid chaos, increase the fluid mixing efficiency and homogenize the system energy distribution. In addition, pulse jet coupling RF-RT impeller system enhances the turbulent characteristics of the fluid, promotes the reduction of the thickness of the liquid film, strengthens the mass transfer and increases the KLa value of the system. When power consumption per unit volume is 360 W/m3, the KLa of the PJ-RF-RT system compared with the PT-R-RT system increases 13.46%, and the KLa of the PJ-R-RT system compared with the SJ-R-RT system increases 11.86%.

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