Mixing Performance Of Multiple Pitched-blade Turbines

In this thesis, the mixing performance of the stirred tank mounted with 4-blade 45° pitched-blade turbines was systematically studied The following parameters, including the liquid height, impeller diameter, impeller numbers, impeller spacing of multiple-impeller system, off-bottom clearance and coil pipe are explored in detail about the influence on the power consumption and mixing performance.The fluid flow structure and vortex were studied through the method of high-speed video camera system. Reasonable explanations of the power consumption and mixing characteristics were given based on the observation of the flow pattern. It was found that the addition of helical coil pipe would enhance the axial circulation flow in the tank, and the power consumption would be higher especially when the rotation speed is pretty high. Also, the effect of the structural parameters and impeller numbers on the mixing characteristics was thoroughly studied through the conductivity method, and an optimized combinations of impellers of different diameter was obtainedThe residence time distribution was studied in the tank mounted with impellers of different diameters. The flow status was evaluated through the analysis of the flow model parameters of the multi-stage totally mixed flow mathematical models. It was found that the variation of those parameters, including off-bottom clearance, impeller diameter, and power consumption, to some extent, would not affect the virtual tank numbers obviously. The flow status in the stirred tank mounted with multiple impellers is similar to the totally mixed flow.