Numerical simulation of tank rotary jet mixers with different nozzle structure

Rotary jet mixers are widely used to purge gunk in crude oil tank and blended oil products. To identify impacts of nozzle structure on performances of mixtures, flat nozzles, Laval nozzles and Venturi nozzles are compared. In addition, ANSYS15.0 is used to simulate the whole fluid field with jetting and blending in oil tank with diameter of 16 m. Moreover, the standard deviation of densities serves as a quantitative index in assessments for performances of the mixture. During simulation, sliding grid is adopted to simulate nozzles' rotating. Standard k-ε model with turbulent flow is adopted as the viscosity model, and mixed model is deployed as the multi-phase flow model. Results of numerical simulation show that both current velocities in Laval and Venturi nozzles are higher than that in flat nozzles under the same flow rate of inlet and outlet, whereas the standard deviation of densities decreases with time. Rotary jet mixers with Laval and Venturi nozzles have mixing performances better than that of those with flat nozzles. The difference is especially high within mixing time of 20-30 min. Laval and Venturi nozzles are good choices for rotary jet mixers deployed in oil tanks.