Research On Single-factor Influencing Laws Of Microbubble Growth And Formation Characteristics

Microbubbles refer to bubbles whose diameter is hundreds of microns.They are small in size They have many characteristics that conventional bubbles do not have,such as small size,slow rise speed,and high mass transfer efficiency.So,microbubbles have considerable potential application value in many fields,such as wastewater treatment,ultrasonic imaging,and skin cleaning.The single-factor inflencing laws of microbubble growth and formation characteristics in the PDMS chip are studied aims to stduy the inflencing laws of microbubble growth and formation characteristics based on the application of microbubbles in sewage treatment and astronauts bathing.The theory model of microbubble formation surrounded by co-flowing liquid was investigated.The mechanics conditions of the microbubble during its growth process are analyzed in detail based on the ellipsoidal assumptions.The mechanical equation of the surface tension,liquid flow tension,gas power and microbubble inertial force are established.The calculation of above-mentioned model was completed to predict the detachment volume of microbubbles in different environments based on the MATLAB and the fourth-order Runge-Kutta method.The numerical simulation experiment of microbubble formation surrounded by co-flowing liquid was investigated.The numerical simulation model was established based on the two-phase flow theory and the level set equations in COMSOL Multiphysics.The detachment volume and formation time in different environments were predicted.And the prediction of the change of the volume in the growth process of the microbubble was completed.The experiments of generation characteristics of the microbubble surrounded by co-flowing liquid was investigated.The PDMS chip based on coaxial flow focusing was processed.A microbubble generation test system was set up to study the generation characteristics of the microbubble surrounded by co-flowing liquid based on the professionally-constucted high-speed microscopic camera system(HSMCS).Image-Pro Plus,Photoshop,and MATLAB are used to process the images in the process of the microbubble generation.The characteristic parameters of the microbubble such as the detachment volume,formation time,and the centroid displacement under different conditions were obtained to investigate the influence of the liquid flow,liquid viscosity,gas pressure and the width of gas channel on generation characteristics of the microbubble.The effect of the prediction of the theoretical model and the simulation model on the detachment volume and the formation time were verified.The experiments of generation characteristics of the microbubble in microfluidicT-junctions was investigated.The PDMS chip based on T-junctions flow focusing was processed.The same experimental system and image processing methods were used to obtain the characteristic parameters of the microbubble such as the detachment volume,formation time,and the process of the change of the volume under different conditions to investigate the influence of the liquid flow,gas pressure and the width of gas channel on the parameters above.The generation frequency of the microbubble and equivalent diameter ratio were set up to compare the effect of the microbubble generation between the coaxial flow focusing and the T-junctions flow focusing environment.In this paper,basic exploration work about the growth and generation characteristics of microbubbles has been carried out.Theoretical models,simulation models,and single-factor influence laws of bubble growth and generation characteristics have provided theoretical support for the controling of the bubble size and generation frequency.Meanswhile,they also provided theoretical support for the engineering application of microbubbles.