Numberical Simulation Of Flow Characteristic And Structure Optimization Of Bubble Generator

Bubble generator has been widely used in flotation,energy,medical treatment and many other fields.Venturi bubble generator is widely used in recent years because of its compact structure and low energy consumption.The flow characteristics of the bubble generator directly affect the foaming performance of the bubble generator.At present,there is little research on the flow characteristics and structural parameters of the bubble generator,so it is of great significance to optimize the working characteristics and structure of the bubble generator.A reasonable three-dimensional physical model is established for the bubble generator in the beginning.After meshing the model accuretely,The PBM model and RNG model are used to simulate flow characteristics of the bubble generator and the particle size of the bubble diameter.The results show that the gas phase enters the larynx from the inlet pipe and is taken away by the high velocity fluid,and the velocity of the gas phase decreases obviously after entering the expansion section.The axial flow is dominant in the two phases in the tube,and with the flow of the two phases,the velocity difference in the radial direction decreases gradually,and the two phases are basically mixed evenly at the outlet of the bubble generator.The pressure changes greatly in the expansion section.According to the result distribution of bubble diameter,the main fragmentation core region of the bubble is near the entrance of the expansion section,and this position is also the peak position of the pressure gradient.It is suggested that the sudden rise of pressure may be related to the breakage of bubbles.In addition,the turbulent kinetic energy increases rapidly near the entrance of the expansion section,which indicates that a large amount of energy exchange occurs in the two phases,and the strong turbulent shear force is another important reason for bubble breakage.By changing the flow rate of the inlet water,the results show that with the increase of water flow rate,the pressure gradient peak and turbulent kinetic energy are increased at the expansion section.The shear force The shear force of bubbles increases with the increase of water flow,and the diameter of bubbles decreases with the increase of water flow rate.In addition,based on the study of the flow characteristics in the bubble generator,different physical models are established by changing the parameters,such as expansion angle,tube diameter and contraction angle.Then,the characteristics of each flow field and the statistical results of the particle size in the pipe are analyzed.The results show that the pressure gradient and turbulent kinetic energy will increase with the increase of the expansion angle,which is beneficial to the breakage of bubbles at the entrance of the expansion stage.But when the expansion angle exceeds a certain range,Small diameter bubbles will produce a certain amountof polymerization at the end of the bubble generator.At the same time,with the increase of the expansion angle,the resistance loss and the energy required at the inlet will increase.With the decrease of the diameter of the pipe,the pressure gradient and turbulent kinetic energy in the expansion section will increase,increasing the shear force on the bubble,the diameter of bubble decreases with the increase of expansion angle.