Effect of blade number on the structure of the trailing vortex around the Rushton turbine impeller is examined by analyzing the data of mean velocities, deformation rates, turbulent kinetic energy and energy dissipation rates for 2-, 4-, 6- and 8-straight blades disk turbine impellers in a baffled standard geometry stirred tank. The data of Sauter mean bubble diameter near the blade tip are combined with the turbulent characteristics around the vortex to discuss how the blade number and the strength of the vortex affect the performance of the gas dispersion around the Rushton turbines under a low gassing rate. The results of this analysis show that if power input per each blade is the same, the impeller having four blades not only has the strongest average mean deformation rates and the largest turbulent kinetic energy, but also disperses the smallest average bubbles under the same gassing rate.
On etudie l'effet du nombre de pales sur la structure du vortex de traǐnee autour de la turbine Rushton en analysant les donnees de vitesses moyennes, de vitesses de deformation, d'energie cinetique turbulente et de taux de dissipation d'energie pour des turbines a disque a 2, 4, 6 et 8 pales droites dans un reservoir agite a contrepales classique. Les donnees du diametre de bulle moyen de Sauter pres de l'extremite de la pale sont combinees aux caracteristiques turbulents autour du vortex pour analyser comment le nombre de pales et la force du vortex influent sur la performance de la dispersion de gaz autour des turbines Rushton a une faible vitesse de gazage. Les resultats de cette analyse montrent que si la consommation de puissance pour chaque pale est la měme, la turbine a quatre pales non seulement a les plus grandes vitesses moyennes de deformation moyenne et la plus grande energie cinetique turbulente, mais egalement qu'elle disperse les plus petites bulles moyennes a la měme vitesse de gazage.
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