Study On The Optimization Of Maxblend Impeller Structure Size By Numerical Simulation

The flow of high viscosity fluid is very complex in the stirred tank, so it is difficult to be obtained flow field in tank by existing experimental condition. At present, the optimization of agitator mainly depends on experience and experiment, and is lack of theoretical direction. However, the experiment usually needs lots of resource and time. Computational Fluid Dynamics (CFD) is used to analyze the fluid flow and heat transfer, which can provide overall flow status and local data in tank. The application of CFD in the optimization of agitator can not only save a lot of resource, but also tremendously improve efficiency.In this work, the influences of a variety of structural parameters on the mixing performance were studied by means of CFD in high viscous xanthan gum solutions. The aim was to optimize the structure size of the maxblend impeller and improve its mixing performance.The multi-reference frame (MRF) technique was used to stimulate impeller motion, shear stress transport (SST) turbulence model and Mixture multiphase flow model were employed in this simulation.To research the impact of the diameter, height, aperture ratio and bottom wing width of the maxblend impeller on its mixing performance. The results showed that there were significant effects of the impeller diameter, height and aperture ratio on its mixing performance, but the bottom wing width had rarely effects on its mixing performance. At a certain extend, enlarging the diameter or height of the impeller, or decreasing impeller aperture ratio could effectively reduce dead-zone volume and improve the carrier gas ability of the maxblend impeller.The distributions of velocity, dead-zone volume, shear rates, apparent viscosity, gas holdup and macro-flow field were studied with different impeller structure size in tanks in order to optimize the structure size of the maxblend impeller and gain its optimum dimensional combination.The structure size of the maxblend impeller was successfully optimized through CFD method in the thesis. Therefore, CFD technique is effective for the optimization of agitator in high viscous system. It can be applied to guide the design, scale-up and optimization of mixing plant.