Effect of Blade Shape on the Performance of Six-Bladed Disk Turbine Impellers

Different modifications of the Rushton turbine were studied in a dual-impeller agitated tank (T = 0.4 m), to find the effect of blade form on power draw, turbulent dispersion, gas handling capacity, mixing, gas holdup, and mass-transfer rate performance under turbulent agitation in an air−water system. Blade streamlining was found to lead to a lower ungassed power number, a higher gas flow number before flooding, and increased insensitivity of impeller power dissipation to the gassing rate. This is consistent with the formation of smaller trailing vortices and ventilated cavities behind the blade. At the same power input and superficial gas velocity, however, the different impellers provided the same mixing time t 0.05, gas holdup εG, and specific mass-transfer coefficient K L a. Each of these variables correlates with the specific power input P G/V L, clearly suggesting that a better performance may be expected after retrofitting of Rushton turbines with streamlined impellers.