Research On Hydraulic Design Of Impeller Blade And Gas-liquid Mixing Characteristics Of Stirred Reactor

Stirring reaction equipment is widely used in chemical industry,biology,metallurgy and other industries.The blade is the core component of the stirring reaction equipment,and its blade structure has an important influence on the dispersion,mixing and reaction rate of the stirring medium.In this paper,a 3m~3 vertical agitator is used as the research object,and the gas-liquid two-phase flow is used as the reaction medium.The method of combining theory and numerical simulation is used to study the stirring characteristics of the blade.In order to obtain better performance propeller blades,first optimize the cross-sectional coefficient k_i,and then use different helix angleγand the shape of the unfolding surface to design four propulsive blades,which are mainly constant spiral symmetric blades(DC-450-32),four propeller blades with variable-spiral symmetric blades(DC-450-γ),constant-helix asymmetric blades(FDC-450-32),variable-spiral asymmetric blades(FDC-450-γ),And the dangerous sections of the four blades are checked and verified to ensure their blade strength.The RNG k-εturbulence model and the VOF multiphase flow model were used to numerically simulate the internal flow fields of the four propeller agitators.The performance of the agitator and the gas-liquid mixing rate at different rotation speeds and different blade geometry parameters were compared.So,the optimal performance of the propeller blades is the variable spiral asymmetric blade(FDC-450-γ),and the effect of the blade installation height of the agitator on the flow field of the agitator is studied,and the optimal blade is selected Installation height.At the same time,due to the trend of large-scale equipment,multi-layer mixers are more and more widely used.Therefore,choosing the proper blade combination is of great significance to improve the mixing performance of the mixer.The optimal variable-helical asymmetric blade(FDC-450-γ)agitator is used as the bottom blade,and the upper layer respectively select propeller blade,4 inclined blade open turbine(45°),4inclined blade disc turbine,4 blades of curved blade turbine get four different combinations of paddle agitators,.Numerical simulations were carried out on four types of agitators with combined blades,and the internal flow field distribution rules of the agitators with different combined blades were studied,and the agitator blade combination with optimal performance was obtained.The research results show that:the power and axial force of the blade increase with the increase of the speed;when the speed is 400r/min,the power and the axial force of the variable spiral symmetric blade(DC-450-γ)is the largest and the power and the axial force of the constant spiral asymmetric blade(FDC-450-32)is the smallest by comparing the four blades.The maximum difference between the power and the axial force is 45.4%and6.9%.the variable spiral asymmetric blade(FDC-450-γ)has the most uniform radial velocity,the largest mixing rate and the shortest mixing time,so the agitating performance of the variable-helical asymmetric blade(FDC-450-γ)is the best.The installation height of the blade is 350mm,which is the optimal installation height.The flow field in the mixing tank is well distributed,and the blade has a good dispersion effect on the gas.The mixing speed is 24s at the fastest,and the installation height is 450mm,with the slowest mixing speed 33s.The lower propeller blade+the upper 4 inclined blade to open the turbine(45°)combined propeller speed distribution is better,the mixing time is short 18s,the energy consumption is small,and it is the combined mixer with the best mixing performance.The mixing time of the combined propeller of the lower propeller blade+the upper 4 curved blade turbine blade is the longest,and the mixing time is 21s.In this paper,through hydraulic design and numerical analysis,The influence of the design parameters of the blade on the mixing performance of the stirred reactor is revealed,and the best performance of the propeller blade is obtained,which can significantly improve the gas-liquid mixing rate and the stirring performance in the stirred reactor.On this basis,the influence of the double-layer combined blade on the mixing performance in the stirred reactor was studied,which provided a theoretical basis for the design and optimization of the blade of the stirred reactor.