Visualization Investigation On Bubble Growth And Motion In Electric Field

Liquid-gas multiphase flow is widely used in industrial production.In a liquid-gas multiphase flow system,the larger contact area between two phases,the larger contact area between two phases results higher heat and mass transfer efficiency between the two phases.Generally,the contact area between phases can be increased by reducing size of bubble.Charged multiphase flow can generate micron-level bubbles to enhance dispersion of liquid-gas multiphase flow,and it also has the advantages about low energy consumption and easy control.It provides a new method for the development of efficient liquid-gas multiphase flow dispersion technology.Current research on charged multiphase flow mainly focuses on charged gas-liquid or liquid-liquid multiphase flow systems,and there are few studies on the growth and dispersion of bubbles in charged liquid-gas multiphase systems.The heat and mass transfer efficiency of the charged liquid-gas two-phase flow is influenced by factors such as the bubble shape change,volume distribution and movement speed in the electric field.Analyzing the bubble growth and movement process and establishing a mathematical model is an important process to explore the bubble dynamics under the action of an electric field.In this paper,the single bubble under non-uniform electric field was taken as the research object.With visualization and image processing technology,the law of bubble growth and evolution in non-uniform electric field was explored.The main research contents and conclusions are as follows:(1)The bubble growth process was visual researched under the electric field.A liquid-gas electrostatic dispersion experiment platform was built,using high-speed digital photography technology and image processing methods to capture the continuous process of bubble growth and evolution,and systematically studied the growth and detachment process of single bubbles at low Re.The experimental results show that the bubble growth process changed significantly under the electric field.The detachment frequency of bubbles increased and the detachment volume decreased.A mathematical model of bubble size was established to get bubble size change theory.(2)The influencing factors of bubble growth process under electric field were experimentally studied.The influence factors of bubble growth process under the electric field were complicated.The influence of dimensionless numbers such as Re,dimensionless diameter,We*,Bo* when bubble growth and detachment process was analyzed.The results show that in the case of low Re,the bubble growth and detachment process was less affected by the flow rate change;The capillary with a smaller diameter generated a larger capillary force,which causes the bubble to detach in different ways;The polarity of the electrode changed the distribution of electric charge on the surface of the bubble.It affected the process of bubble growth.(3)The bubble velocity was analyzed under the electric field by using the liquidgas electrostatic dispersion experimental platform.PIV technology was used to analyze the law of the moving speed after the bubble detached.The results show that the electric field increased the initial velocity after the bubble detaches and increases the lateral velocity of the bubble movement.This enhanced the dispersion of bubbles in the liquid.