Influence of impeller type on the flow structure in a stirred reactor

Large eddy simulations (LES) of a stirred reactor with a liquid volume of 0.64 m(3) were performed. The tank was stirred by either two standard Rushton impellers or two Scaba 6SRGT impellers. The LES can provide details of the flow field that cannot be obtained with so-called Reynolds-averaged equations and the corresponding models. The unsteady spatially filtered incompressible Navier-Stokes equations were solved together with a transport equation for the concentration of an inert additive using a multigrid finite difference code with a staggered grid. The unresolved turbulent scales were modeled using a scale similarity model. The aim of this investigation has been to study the influence of impeller type on the flow structure and scalar transport. The results show that, compared at equal power input, the center plane velocities and the volume flow in the impeller stream do not differ much for the impeller types. Also, for the 6SRGT the periodic fluctuations associated with the blade passing is less pronounced.