The gas-liquid countercurrent flow pattern is complex and the bubble migration velocity is difficult to predict in the process of bullheading well killing.The experiment on bubble migration in gas-liquid countercurren...The gas-liquid countercurrent flow pattern is complex and the bubble migration velocity is difficult to predict in the process of bullheading well killing.The experiment on bubble migration in gas-liquid countercurrent flow in annulus is carried out under different working conditions to reveal how the wellbore inclination angle,liquid phase property and countercurrent liquid velocity affect the bubble deformation and bubble migration trajectory/velocity,and to establish a bubble migration velocity prediction model.The bubbles in the countercurrent flow mainly migrate in two modes:free rising of isolated bubbles,and interactive rising of multiple bubbles.The bubbles migrate by an S-shaped trajectory in the countercurrent flow.With the increase of countercurrent liquid velocity,the lateral oscillation of bubbles is intensified.The increases of wellbore inclination angle,liquid density and liquid viscosity make the bubble migration trajectory gradually to be linear.The bubble is generally ellipsoidal during its rising.The wellbore inclination angle has little effect on the degree of bubble deformation.The bubbles are ellipsoidal during rising,with little influence of wellbore inclination angle on bubble deformation.With the increase of liquid viscosity and density,the aspect ratio of the bubble decreases.As the wellbore inclination angle increases,the bubble migration velocity gradually decreases.As the liquid viscosity increases,the bubble migration velocity decreases.As the liquid density increases,the bubble migration velocity increases slightly.The established bubble migration velocity prediction model yields errors within±15%,and demonstrates broad applicability across a wide range of operating conditions.展开更多
The presence of a rigid wall causes a microjet of the cavitation bubble to collapse to move toward the wall,while a free surface does the opposite.When a rigid wall surface is combined with a free surface,it may affec...The presence of a rigid wall causes a microjet of the cavitation bubble to collapse to move toward the wall,while a free surface does the opposite.When a rigid wall surface is combined with a free surface,it may affect the direction of the microjet.The motive of this study is to find out the influence of the dynamic behavior of a laser-induced bubble near the rigid wall with a gas-containing hole.Evolutions of the bubble at different distances from the gas-containing hole in the horizontal and vertical directions were recorded by a high-speed camera(2.3×10^(5) fps).When the bubble collapse near the boundary,the bubble will produce two situations:away from or toward the boundary.It focuses on the direction of the bubble,the oscillation period of a bubble,and reflection angle,and quantitative analysis of the results.It was found that the boundary not only changes the morphologic of the bubble and the overall direction of movement but also affects the oscillation period.In addition,it can control the deflection of the bubble.展开更多
Condition monitoring and maintenance are essential for ensuring stable and reliable operation of facility transformer,reducing costs,and increasing expected life.Foam cannot be avoided within the power transformer whi...Condition monitoring and maintenance are essential for ensuring stable and reliable operation of facility transformer,reducing costs,and increasing expected life.Foam cannot be avoided within the power transformer which illustrates at least one of the principal roots of insulation deterioration.Due to the intricacy of the dynamics within the insulation system,involving bubble creation,migration,and accumulation,challenges arise in understanding these mechanisms.Consequently,the problems caused by bubble dynamics require further investigation.This paper provides a scientific review of issues related to bubble formation,migration,and dispersion and their electrical effects on power transformers.Various descriptions are given to highlight impact of the dynamics of the bubble within high voltage insulation fields,which covers bubble generation mechanism,and therefore,the quintessential influencing factors,state-ofthe-art advances in multi-physics coupled modeling of bubble dynamics,etc.Moreover,pending issues on bubble control and mitigation are addressed,as well as recommendations for future investigations.Nonetheless,this paper contains a useful quotation guide for researchers within an equivalent field of research,which can motivate readers to explore scientific solutions to prevailing bottleneck problems.展开更多
基金Supported by the National Natural Science Foundation of China(U21B2069,52274020,52288101,52274022)National Key Research and Development Program of China(2022YFC2806504)。
文摘The gas-liquid countercurrent flow pattern is complex and the bubble migration velocity is difficult to predict in the process of bullheading well killing.The experiment on bubble migration in gas-liquid countercurrent flow in annulus is carried out under different working conditions to reveal how the wellbore inclination angle,liquid phase property and countercurrent liquid velocity affect the bubble deformation and bubble migration trajectory/velocity,and to establish a bubble migration velocity prediction model.The bubbles in the countercurrent flow mainly migrate in two modes:free rising of isolated bubbles,and interactive rising of multiple bubbles.The bubbles migrate by an S-shaped trajectory in the countercurrent flow.With the increase of countercurrent liquid velocity,the lateral oscillation of bubbles is intensified.The increases of wellbore inclination angle,liquid density and liquid viscosity make the bubble migration trajectory gradually to be linear.The bubble is generally ellipsoidal during its rising.The wellbore inclination angle has little effect on the degree of bubble deformation.The bubbles are ellipsoidal during rising,with little influence of wellbore inclination angle on bubble deformation.With the increase of liquid viscosity and density,the aspect ratio of the bubble decreases.As the wellbore inclination angle increases,the bubble migration velocity gradually decreases.As the liquid viscosity increases,the bubble migration velocity decreases.As the liquid density increases,the bubble migration velocity increases slightly.The established bubble migration velocity prediction model yields errors within±15%,and demonstrates broad applicability across a wide range of operating conditions.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91852101,91952301,52179092 and 52179081).
文摘The presence of a rigid wall causes a microjet of the cavitation bubble to collapse to move toward the wall,while a free surface does the opposite.When a rigid wall surface is combined with a free surface,it may affect the direction of the microjet.The motive of this study is to find out the influence of the dynamic behavior of a laser-induced bubble near the rigid wall with a gas-containing hole.Evolutions of the bubble at different distances from the gas-containing hole in the horizontal and vertical directions were recorded by a high-speed camera(2.3×10^(5) fps).When the bubble collapse near the boundary,the bubble will produce two situations:away from or toward the boundary.It focuses on the direction of the bubble,the oscillation period of a bubble,and reflection angle,and quantitative analysis of the results.It was found that the boundary not only changes the morphologic of the bubble and the overall direction of movement but also affects the oscillation period.In addition,it can control the deflection of the bubble.
基金supported in part by the Science and Technology Project of SGCC:Research on bubble generation mechanism and behavior characteristics of oil-immersed power transformer/high-voltage reactor under the coupling action of vibration and electric field(No.52120520001A).
文摘Condition monitoring and maintenance are essential for ensuring stable and reliable operation of facility transformer,reducing costs,and increasing expected life.Foam cannot be avoided within the power transformer which illustrates at least one of the principal roots of insulation deterioration.Due to the intricacy of the dynamics within the insulation system,involving bubble creation,migration,and accumulation,challenges arise in understanding these mechanisms.Consequently,the problems caused by bubble dynamics require further investigation.This paper provides a scientific review of issues related to bubble formation,migration,and dispersion and their electrical effects on power transformers.Various descriptions are given to highlight impact of the dynamics of the bubble within high voltage insulation fields,which covers bubble generation mechanism,and therefore,the quintessential influencing factors,state-ofthe-art advances in multi-physics coupled modeling of bubble dynamics,etc.Moreover,pending issues on bubble control and mitigation are addressed,as well as recommendations for future investigations.Nonetheless,this paper contains a useful quotation guide for researchers within an equivalent field of research,which can motivate readers to explore scientific solutions to prevailing bottleneck problems.
