Measurement And Numerical Simulation Of Gas-Liquid Two Phase Flow In Jet Micro-Bubble Generator

In the flotation,air is dispersed in the flotation system in the form of bubbles,and the bubbles serve as carriers to bring the target mineral adhered thereto to the liquid surface.The jet microbubble generator is used to generate a certain size and number of microbubbles.The structural parameters directly affect the improvement of the flotation efficiency.As the bubbles move together in a high-speed fluid,they will gather and break,and the internal flow field movement law and behavior of the device.Unusually complicated.This article uses computational fluid dynamics(CFD),particle image measurement(PIV),and high-speed dynamic microscopy techniques to study the clean water-bubble two-phase flow field of laboratory jet microbubble generators.The research was conducted: firstly,the PIV and high-speed dynamic flow field tests were performed.By numerical simulation and experimental data comparison,a numerical model suitable for the computation of complex flow fields in jet microbubble generators was established.On this basis,the optimal design of the jet microbubble generator was achieved through PIV measurement and using the established numerical model.The main work and conclusions are as follows:A test-circulation system for clear water-bubbles in a laboratory jet microbubble generator was set up.The PIV and high-speed dynamic technology were used to test the two-phase flow field with single-tube 45° downward intake structure at low gas holdup rate,and the bubble velocity was obtained.The characteristics of the size distribution provide the basis for subsequent numerical calculation model exploration and structural comparison after experimental optimization.A two-phase fluid dynamics numerical model suitable for the calculation of clean waterbubble flow field in jet microbubble generator was established.The numerical simulation of the jet microbubble generator with single-pipe downward-inlet structure was carried out.Compared with the experimental measurement,the results show that the Euler-Euler two-fluid(E-E TFM)model deals with the gas-liquid two-phase calculation;based on the group equilibrium.The polyhedral model and Lehr fracture model in the model(PBM)are used to calculate the collapse and collapse of bubbles;the turbulence is calculated using the renormalized RNG k-? model;the drag force is calculated using the Tomiyama model;the lift is calculated using the Tomiyama model;and Antal-is used The et-al model calculates the wall lubricity;the numerical results that are most consistent with the experimental measurements are obtained.Based on the above calculation model,the distribution of gas holdups in the single-pipe down-intake structure is analyzed by numerical simulation results,which shows that there are eccentric movements of bubbles in this structure,and actual industrial applications will cause equipment wear.The number of inlet tubes was optimized,and a double inlet tube structure was designed.Through experimental measurements and numerical simulations of the jet microbubble generator of this structure,the results showed that the double tube symmetrical downward inlet structure was lower than the single tube downward inlet.The structure can reduce the size of the bubble,and has no obvious influence on the axial velocity of the bubble,so that the radial velocity of the bubble becomes larger.Double-pipe symmetrical downward intake structure improves bubble eccentricity.Based on the double-pipe symmetric downward intake structure,a double-pipe downward and tangential intake pipe structure is designed.The numerical simulation results show that the double-pipe tangential intake structure is lower than the double pipe symmetrical downward intake structure to make bubbles More evenly distributed.In addition,the two-tube vertical tangential air intake structure is also discussed.The results show that the dual-pipe down and tangential air intake structure and the dual-tube vertical tangential air intake structure can improve the phenomenon of eccentric bubble movement.The tangential air intake structure Compared with the vertical tangential air intake structure,the air bubble distribution is more uniform,and the tangential air intake structure is better in improving the average particle diameter of the air bubbles.