Chaotic Mixing Enhanced By Flexible Stirring Shaft In Stirred Vessel

The stirring shaft is one of the core components of the stirred reactor. The structure and parameters of the mixing reactor directly influence the performance of the fluid mixing in the stirred reactor. The stirring reactor is driven by the power output device to driving the stirring shaft and the stirring paddle to rotate, so as to obtain the proper flow field, the heat transfer and the mass transfer of the process, and the production efficiency and the ability are improved. However, it was found that the structure of periodic and symmetrical flow field was easy to form in the vicinity of the traditional rigid mixing shaft, which could reduce the mixing efficiency of the fluid. And the rigidity of the mixing shaft in the rotating speed was larger, would produce a total shock phenomenon, and the reactor was connected to all the pipes were a severe beating, there was a certain security risk. Therefore, in the development of structural optimization of stirring shaft, a profound understanding of the enhanced nonlinear dynamics of fluid mixing processes, direct and efficient energy-saving mixing reactor was developed and applied, and had important theoretical significance and practical value.This work takes flexible stirring shaft as the research object, from the mixing process of strengthening, respectively with water and high viscosity liquid experiment. By research flexible mixing shaft with force analysis and different proportion, stirring paddle speed, flexible sheet length and rigid flexible impeller combination form of mixing of fluid flow in the reactor and chaotic characteristic parameters, combined with wavelet analysis and MATLAB software, computing power consumption per unit volume(PV), the largest Lyapunov exponent LEmax and multiscale entropy(MSE) of stirring and the characteristics of chaotic mixing in the fluid in the reactor; at the same time, the use digital camera shooting recording and mixing reactor in liquid- liquid two- phase mixing process, and record the corresponding mixing time. The main conclusion of this thesis are as follows:(1)At the same speed, the torque of the rigid shaft is larger than the flexible shaft under different proportions. The greater the torque value, the greater the torsional shear stress formed on the cross section of the stirring shaft, and the larger the failure of the stirring shaft. With a rigid stirring shaft compared to flexible stirring shaft through active links have eliminated part of the torque, certain extent inhibited the speed is too large to bring the resonance phenomena, and enlarges the mixing region, directly promote and strengthen the mixing energy transfer and diffusion.(2)For low viscosity system and high viscosity system, with the increase of power consumption, the mixing time of the rigid shaft system and the flexible shaft system is reduced, and the lntmix has a better linear relationship with the change of ln PV. For the system of low viscosity, flexible stirring shaft system is rigid stirring shaft system of fluid mixing time relationship 73.49%; for the system with high viscosity and flexible stirring shaft system is rigid stirring shaft system of fluid mixing time relationship 65.34%.(3)For low viscosity and high viscosity, rigid mixing shaft and the flexible mixing two axis system LEmax were greater than zero and trend with power consumption of unit volume increases and increases first and then decreases, indicating that the system has entered a state of chaos. For low viscosity system, compared with both of them, the flexible stirring shaft system in the low power hybrid can achieve very well, and the maximum LEmax value increased 12.57%. For the high viscosity system, compared with both of them, the LEmax value of flexible stirring shaft system greater than rigid stirring shaft system for increasing the 10.45%.(4)For low viscosity and high viscosity, rigid stirring shaft system LEmax are smaller, and the illustrates that chaos degree of the system is low, the system entropy is lower, and flexible stirring shaft system LEmax relatively large, trajectories of motion of fluid in the system is relatively complex, which leads to the entropy is higher.