Turbulence Characteristics Of Off-bottom Solids Suspension In Bottom Of Solid-Liquid Square Stirred Tank

Solid-liquid mixing is widely used in the petrochemical industry. Measurement of the solid-liquid flow field is very important to study of the mechanism on suspended solids and two-phase flow field changing, It is also beneficial to understand the flow characteristics of stirred tank.In this paper, the study measured the turbulent flow field at the area which is2mm from the bottom of stirred tank by using Two-dimensional Particle Image Velocimetry. It is performed in a flat bottomed cubic tank with a3-blade CBY that the diameter is0.075m.The tank is equipped with no baffles. Liquid turbulence flow fields is studied with five different off-bottom clearances at the bottom area under the critical state.In addition, physical changes (including particle size and particle density) of turbulent flow field under the influence of the critical state of suspension.Experimental results show that with the increase of C/T, impeller speed at solid critical suspension is increased; At different locations in the tank bottom, there are different Njs and the factors which influent solid suspended is not the same. When C is less than0.4T, at main flow area and near wall area in the tank solid phase is suspended by the mean flow and turbulent; the solid phase suspension is mainly affected by turbulent fluctuations and mean flow played a secondary role in the bottom corner of the tankFor the characteristics of the material nature of the result of the suspension, increasing the diameter and density of the solid particles can lead to Njs, mean velocity and turbulence fluctuating velocity around the particle increase, there is a liner relationship between the pulse velocity and Njs. In addition, various physical properties of the solid phase have a maximum impact on the bottom turbulent kinetic energy dissipation rate at tank bottom, and also turbulent velocity fluctuations is affected minimally.