| Stirred vessels equipped with disc turbines are widely used in manyindustry processes, such as petrochemical, biochemical, pharmaceutical andfood industry. The flow fields in the stirred tanks are complex, finding ameasuring method to study the mixing turbulent dynamic characteristics isour primary work.The phase resolved3D-PIV technique (Stereo PIV) with highresolution and2D-PIV were used in a perspex vessel of476mm in diameter,in which the depth of tap water was equal to the diameter of the vessel. Themean velocity, root meall square (rms) velocity, trailing vortex, turbinekinetic energy (TKE) and anisotropy were investigated.With the help of λ2and Lumley-Newman triangle methods, theexperiment told the influences of different Reynolds number (Re=40000,50000,60000,75000and90000) and different types of impellers (Rushtonturbine, concaved blade disk turbine and half elliptical-blade diskturbine).The results showed that with the increasing curvature of the blades,the input power was saved, the tangential velocity was reduced, vortex pairwas protected for a longer time at the tip of blades, and the skewness degreeof the jet flow was weakened. The turbulent kinetic energy in the position oftrailing vortex for the HEDT was a little bigger than the others, while the CDimpeller flow field had the biggest maximum value of the TKE. In the impeller jet region, and in the area near trailing vortices, the turbulence wasfar from being isotropic; the turbulence was more isotropic with increasingcurvature of the blades, isotropy showed independence of the Re. The TKEcalculated from2D PIV data with the help of pseudo-isotropic assumptionwas overvalued by some28%in comparison with those calculated from3Ddata. The velocity and rms velocity results of2D and3D PIV werecoincident.The research provided amount of base data of fluid turbulentcharacteristics in the stirred tank equipped with RT, CD or HEDT impellersfor the CFD simulations and subsequent experiments. |
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