Numerical and experimental study on flow and mixing behaviour of transverse turbulent jet in venturi-jet mixer

Abstract

An investigation of the jet trajectories and mixing behaviour of venturi-jet mixers to mix incompressible fluids in which turbulent jet injects fluid at an arbitrary angle have been studied experimentally and numerically by writing conservation equations in natural coordinate system and also by using FLUENT CFD code. Numerical results of an incompressible cross flow-jet mixing in venturi-jet mixers are presented and validated against experimental results. Twenty five cases were studied, including 5 different initial injection angles 45o, 60o, 90o, 120o, 135o and 25 different jet momentum ratios to evaluate the entrainment of jet and mixing performances of the mixer. The experiments show that the performance of a venturi-jet mixer substantially improves at high injection angle and can be augmented still by increasing velocity ratio. The effect could contribute substantially to the better mixing index with moderate pressure drop. In contrast, the jet deflects much and penetrates less in the cross flow with increase of cross flow Reynolds number. The comparison between the experimental and numerical results confirms the accuracy of the simulations. The results show a consistency in the experimental data and simulation has provided a good insight into the flow details and has paved the way for optimisation in the geometrical design based on jet injection angle, cross flow Reynolds number and velocity ratio to get a good mixing efficiency. In this work, computational simulation of three dimensional flow mixing process of turbulent jet with cross flow in a venturi-jet mixer by using a standard Computational Fluid Dynamics (CFD) solver is also presented. Also a comparison of numerical results and measured data for flow mixing process in the venturi-jet mixer was made to check the results of numerical simulations. The venturi-jet mixer has been demonstrated to provide a superior approach for the mixing concept with static mixer systems over commonly used T-mixer system.