We report the observation of bubble generation and migration in a germanate g/ass during irradiation by a femtosecond laser of high repetition rate. Bubbles are formed around the focal area of the laser beam, and thei...We report the observation of bubble generation and migration in a germanate g/ass during irradiation by a femtosecond laser of high repetition rate. Bubbles are formed around the focal area of the laser beam, and their movement indicates the presence of thermal gravity convection in the glass melt, which is beyond the existing theoretical model about temperature l^eld of focal area. Inside the bubbles, oxygen molecules are observed by the con focal Raman micro-spectroscopy. The generation of molecular oxygen and bubbles is explained in terms of the spatial separation of Ge and 0 ions and micro-explosion inside the glass melt.展开更多
The interphase mass,heat transfer efficiency,and flow resistance are strongly dependent on bubble size in gas-liquid two-phase systems,so it is very important for engineering applications to effectively control bubble...The interphase mass,heat transfer efficiency,and flow resistance are strongly dependent on bubble size in gas-liquid two-phase systems,so it is very important for engineering applications to effectively control bubble size.In this paper,the formation,growth,and detachment of single bubbles in Newtonian liquids based on capillary needles were studied in detail using a volume of fluid method.The authors investigated the effects of gas injection velocity,gravitational level,surface tension coefficient,needle radius,and liquid-phase properties(liquid viscosity and density)on the process of bubble generation,and the effects of the above factors on bubble shape,detachment diameter,and time were analyzed.The results show that an increase in gas injection rate,liquid-phase viscosity,needle radius,and surface tension coefficient can lead to an increase in bubble detachment diameter;however,an increase in liquid-phase density and gravitational level can lead to a decrease in bubble detachment diameter.It is found that the effect of the liquid-phase viscosity on bubble detachment diameter and time is slight,but the effect of gravitational level on detachment diameter and time is significant.Among all the forces,buoyancy,surface tension,and pressure are the most important ones that control the generation of bubbles.展开更多
The interturn paper insulation of oil-immersed power transformer windings,under the combined influence of electric fields,moisture,and conductor heating,will produce bubbles,which pose a significant threat to the insu...The interturn paper insulation of oil-immersed power transformer windings,under the combined influence of electric fields,moisture,and conductor heating,will produce bubbles,which pose a significant threat to the insulation system.However,there is limited research on the characteristics of bubble evolution in oil-paper insulation under the influence of electric fields and the subsequent dissolution process.Based on the continuous observation of bubble size using electron microscopes,experimental and theoretical investigations into the formation and dissolution of bubbles under electric field conditions are presented.The effects of different field strengths on bubble evolution and dissolution characteristics were studied.The results showed that the electric field promoted both the generation and dissolution of bubbles,with a more pronounced effect observed at higher field strengths(below partial discharge(PD)inception electric field,hereafter referred to as PDIE).However,when the field strength exceeded PDIE,the bubbles tended to shrink and gradually increase in size.The changes in bubble volume were related to not only gas diffusion but also oxygen consumption and fault gases generation due to PD.A better understanding of the formation and dissolution characteristics of bubbles under varying field strengths is achieved.Furthermore,it also provides a reference for assessing the risk of bubble generation and conducting bubble-related fault diagnosis during the overload operation of oil-immersed power equipment.展开更多
The flotation process is a particle-hydrophobic surface-based separation technique. To improve the essential flotation steps of collision and attachment probabilities, and reduce the step of detachment probabilities b...The flotation process is a particle-hydrophobic surface-based separation technique. To improve the essential flotation steps of collision and attachment probabilities, and reduce the step of detachment probabilities between air bubbles and hydrophobic particles, a selectively designed cavitation venturi tube combined with a static mixer can be used to generate very high numbers of pico and nano bubbles in a flotation column. Fully embraced by those high numbers of tiny bubbles, hydrophobic particles readily attract the tiny bubbles to their surfaces. The results of column flotation of Pittsburgh No. 8 seam coal are obtained in a 5.08 cm ID and 162 cm height flotation column equipped with a static mixer and cavitation venturi tube, using kerosene as collector and MIBC as frother. Design of the experimental procedure is combined with a statistical two-stepwise analysis to determine the optimal operating conditions for maximum recovery at a specified grade. The effect of independent variables on the responses has been explained. Combustible material recovery of 85–90% at clean coal product of 10–11% ash is obtained from feed of 29.6% ash, with a much-reduced amount of frother and collector than that used in conventional column flotation. The column flotation process utilizing pico and nano bubbles can also be extended to the lower limit and upper limit of particle size ranges, minus 75 lm and 300–600 lm, respectively, for better recovery.展开更多
We demonstrate the possibility of detection and monitoring of bubbles emerging near the tip of an optical fiber by means of ultrasonic method.The excitation of bubbles at their resonant frequencies is performed using ...We demonstrate the possibility of detection and monitoring of bubbles emerging near the tip of an optical fiber by means of ultrasonic method.The excitation of bubbles at their resonant frequencies is performed using short ultrasonic pulses having a wide frequency range simulta-neously with their modulation by means of a long pulse of a monochromatic frequency.This method allows detection of bubbles of various sizes.Used signal processing method,which allows increased bubble detection accuracy,is proposed for ressearch in envir onments of biological-like medium which show continuous variations in structure and properties when exposed to optical emission.The method has been demonstrated on model objects:in a liquid and in a biological tissue phantom using various methods of bubble generation(hydrolysis and optical enission).We studied bubble formation by the tip of a fiber of the surgical laser LSP-007/10 "IRE Polus"with a wavelength of 0.97μm coated with a highly absorbing graphite layer.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 51132004 and 61475047the National Basic Research Program of China under Grant No 2011CB808100+2 种基金the Natural Science Foundation of Guangdong Province under Grant No S2011030001349the Fundamental Research Funds for the Central Universities under Grant No 2013ZM0001the Open Fund of the State Key Laboratory of High Field Laser Physics of Shanghai Institute of Optics and Fine Mechanics
文摘We report the observation of bubble generation and migration in a germanate g/ass during irradiation by a femtosecond laser of high repetition rate. Bubbles are formed around the focal area of the laser beam, and their movement indicates the presence of thermal gravity convection in the glass melt, which is beyond the existing theoretical model about temperature l^eld of focal area. Inside the bubbles, oxygen molecules are observed by the con focal Raman micro-spectroscopy. The generation of molecular oxygen and bubbles is explained in terms of the spatial separation of Ge and 0 ions and micro-explosion inside the glass melt.
文摘The interphase mass,heat transfer efficiency,and flow resistance are strongly dependent on bubble size in gas-liquid two-phase systems,so it is very important for engineering applications to effectively control bubble size.In this paper,the formation,growth,and detachment of single bubbles in Newtonian liquids based on capillary needles were studied in detail using a volume of fluid method.The authors investigated the effects of gas injection velocity,gravitational level,surface tension coefficient,needle radius,and liquid-phase properties(liquid viscosity and density)on the process of bubble generation,and the effects of the above factors on bubble shape,detachment diameter,and time were analyzed.The results show that an increase in gas injection rate,liquid-phase viscosity,needle radius,and surface tension coefficient can lead to an increase in bubble detachment diameter;however,an increase in liquid-phase density and gravitational level can lead to a decrease in bubble detachment diameter.It is found that the effect of the liquid-phase viscosity on bubble detachment diameter and time is slight,but the effect of gravitational level on detachment diameter and time is significant.Among all the forces,buoyancy,surface tension,and pressure are the most important ones that control the generation of bubbles.
基金State Grid Corporation of China,Grant/Award Number:5500-202116119A。
文摘The interturn paper insulation of oil-immersed power transformer windings,under the combined influence of electric fields,moisture,and conductor heating,will produce bubbles,which pose a significant threat to the insulation system.However,there is limited research on the characteristics of bubble evolution in oil-paper insulation under the influence of electric fields and the subsequent dissolution process.Based on the continuous observation of bubble size using electron microscopes,experimental and theoretical investigations into the formation and dissolution of bubbles under electric field conditions are presented.The effects of different field strengths on bubble evolution and dissolution characteristics were studied.The results showed that the electric field promoted both the generation and dissolution of bubbles,with a more pronounced effect observed at higher field strengths(below partial discharge(PD)inception electric field,hereafter referred to as PDIE).However,when the field strength exceeded PDIE,the bubbles tended to shrink and gradually increase in size.The changes in bubble volume were related to not only gas diffusion but also oxygen consumption and fault gases generation due to PD.A better understanding of the formation and dissolution characteristics of bubbles under varying field strengths is achieved.Furthermore,it also provides a reference for assessing the risk of bubble generation and conducting bubble-related fault diagnosis during the overload operation of oil-immersed power equipment.
基金provided by West Virginia State Coal and Energy Research Bureau (CERB)the Department of Mining Engineering,West Virginia University
文摘The flotation process is a particle-hydrophobic surface-based separation technique. To improve the essential flotation steps of collision and attachment probabilities, and reduce the step of detachment probabilities between air bubbles and hydrophobic particles, a selectively designed cavitation venturi tube combined with a static mixer can be used to generate very high numbers of pico and nano bubbles in a flotation column. Fully embraced by those high numbers of tiny bubbles, hydrophobic particles readily attract the tiny bubbles to their surfaces. The results of column flotation of Pittsburgh No. 8 seam coal are obtained in a 5.08 cm ID and 162 cm height flotation column equipped with a static mixer and cavitation venturi tube, using kerosene as collector and MIBC as frother. Design of the experimental procedure is combined with a statistical two-stepwise analysis to determine the optimal operating conditions for maximum recovery at a specified grade. The effect of independent variables on the responses has been explained. Combustible material recovery of 85–90% at clean coal product of 10–11% ash is obtained from feed of 29.6% ash, with a much-reduced amount of frother and collector than that used in conventional column flotation. The column flotation process utilizing pico and nano bubbles can also be extended to the lower limit and upper limit of particle size ranges, minus 75 lm and 300–600 lm, respectively, for better recovery.
基金financial support from grant 14-15-00840 of the Russian Scientific Fund.
文摘We demonstrate the possibility of detection and monitoring of bubbles emerging near the tip of an optical fiber by means of ultrasonic method.The excitation of bubbles at their resonant frequencies is performed using short ultrasonic pulses having a wide frequency range simulta-neously with their modulation by means of a long pulse of a monochromatic frequency.This method allows detection of bubbles of various sizes.Used signal processing method,which allows increased bubble detection accuracy,is proposed for ressearch in envir onments of biological-like medium which show continuous variations in structure and properties when exposed to optical emission.The method has been demonstrated on model objects:in a liquid and in a biological tissue phantom using various methods of bubble generation(hydrolysis and optical enission).We studied bubble formation by the tip of a fiber of the surgical laser LSP-007/10 "IRE Polus"with a wavelength of 0.97μm coated with a highly absorbing graphite layer.
