1 INTRODUCTIONBubble diameter distribution and gas holdup are very important parameters indicatingthe characteristics of gas-liquid dispersion,works done are mostly experimentalobservation.Theoretical analysis of bubb...1 INTRODUCTIONBubble diameter distribution and gas holdup are very important parameters indicatingthe characteristics of gas-liquid dispersion,works done are mostly experimentalobservation.Theoretical analysis of bubble diameter has been mostly focused on thebreak-up of bubbles in the impeller region,and only the theoretical relationship be-tween bubble diameter and operating variables in the impeller region has been展开更多
Adaptive neuro fuzzy inference system (ANFIS) procedure and regression methods were used to predict the Sauter mean bubble (bubble diameter) and surface area flux of the bubble in a flotation process. The operational ...Adaptive neuro fuzzy inference system (ANFIS) procedure and regression methods were used to predict the Sauter mean bubble (bubble diameter) and surface area flux of the bubble in a flotation process. The operational conditions of flotation, impeller peripheral speed, superficial gas velocity, and weight percent solids were used as inputs of methods. By using the mentioned operational conditions, the non linear regression results showed that Sauter mean, and surface area flux of the bubble are predictable variables, where the coefficients of determination (R 2 ) are 0.57 and 0.74, respectively. To increase the accuracy of prediction an ANFIS model with cluster radius of 0.4 was applied. ANFIS model was capable of estimating both Sauter mean, and surface area flux of the bubble, where in a testing stage, satisfactory correlations, R 2 = 0.78, and 0.86, were achieved for Sauter mean, and surface area flux of bubble, respectively. Results show that the proposed ANFIS model can accurately estimate outputs and be used in order to predict the parameters without having to conduct the new experiments in a laboratory.展开更多
The properties and thickness of the bubbles in the froth control the flotation process. There is no work showing how to measure bubble film composition and thickness by a straightforward manner. In this work, a novel ...The properties and thickness of the bubbles in the froth control the flotation process. There is no work showing how to measure bubble film composition and thickness by a straightforward manner. In this work, a novel approach, a custom-designed bubble cell associated with layer interferometry(in the UV-vis region) and FT-IR spectroscopy was used to investigate the effect of solid particle type(hydrophilic vs hydrophobic), concentration and bubble diameter on stability of a bubble blown in air. Stability was quantified by measuring bubble lifetime and hydrated film thickness. Kerosene with silicone oil as a foaming agent was used to evaluate the impact of bubble diameter(test series I). Frother solutions(MIBC, Dowfroth 250, Hexanol and F-150) were used for the solid type concentration experiments(test series II). In the first series of experiments, it was determined that as the diameter of a bubble increased from 10 to 25 mm, so did the hydrated film thickness from 350 to 1000 nm. In the second series, as the silica concentration increased(0 to 10%), an increase in bubble lifetime and hydrated film thickness was resulted(130%-250%). An impact of solid hydrophobicity was found but to a lesser degree than expected. It is possible that the small particle size(<0.1 m) of silica was responsible for this behavior. The findings are used to interpret the effect of solids in flotation froth.展开更多
Xenon was used as the gas phase to investigate the hydrodynamic characteristics in a bubble column.It was found that the flow pattern is mainly in the churn-turbulent flow regime through analysing the relationship bet...Xenon was used as the gas phase to investigate the hydrodynamic characteristics in a bubble column.It was found that the flow pattern is mainly in the churn-turbulent flow regime through analysing the relationship between the slip velocity and gas holdup.The influence of operating conditions on the gas holdup and the Sauter mean diameter was studied.The experimental results show that the Sauter mean diameter decreases with the increase of energy dissipation rate.A new correlation was developed to predict the Sauter mean diameter with an average error of less than 15%.展开更多
Experiments on subcooled flow boiling have been conducted using water in a rectangular flow channel.Similar to the coolant channel in internal combustion engines(IC engines),the flow channel in this experiment was asy...Experiments on subcooled flow boiling have been conducted using water in a rectangular flow channel.Similar to the coolant channel in internal combustion engines(IC engines),the flow channel in this experiment was asymmetrically heated.Bubble images were captured using a high speed camera from the side view of the channel.The experimental conditions in terms of bulk temperature,bulk velocity,pressure and heat flux ranged from 65°C–75°C,0.25 m/s–0.75 m/s,1–1.7 bar and 490 kW/m2–700 kW/m2,respectively.On the basis of these tests,a statistical analysis of the bubble size has been conducted considering a population of 1400 samples.It has been found that the mean Sauter bubble diameter increases with the decrease of subcooling,bulk velocity,pressure and increased heat flux.A modified correlation has been finally proposed to predict the mean Sauter bubble diameter under subcooled flow boiling conditions upstream of the onset of significant void,which shows good accuracy with the experimental results.展开更多
The flow behavior of gas and solid was investigated in FCC simulator of φ710×4000/φ870×11000mm.The axial and radial distributions were detected with matrix fiber-opticprobes.It was found that the distribut...The flow behavior of gas and solid was investigated in FCC simulator of φ710×4000/φ870×11000mm.The axial and radial distributions were detected with matrix fiber-opticprobes.It was found that the distribution of bubble diameter in the turbulent region of the fluidizedbed of fine particles was different from the results reported for lab-scale experiments.Radially therewere three areas,i.e.,the central(r/R=0-0.4),the intermittent or stable(r/R=0.4-0.8)and thenear wall(r/R=0.8-1.0)areas respectively.It was noticed that bubbles were almost non-existing atthe near wall area.Hence,according to the coalescence and splitting theory of bubbles,a two-areamodel of bubble diameter distribution was proposed and a dimensionless parameter(γ_M)regarded asan index for’quality’of fluidization was deduced.展开更多
Based on the comprehensive forces balance model, a modified model of the formation of a single bub-ble in non-Newtonian fluid under constant flowrate was developed by taking account of the effect of the ingoing gas th...Based on the comprehensive forces balance model, a modified model of the formation of a single bub-ble in non-Newtonian fluid under constant flowrate was developed by taking account of the effect of the ingoing gas through orifice as well as its variation on the radial expansion of bubble. The modified model involves the radial expansion equation of bubble surface and the forces balance equation in vertical direction of the bubble respec-tively. The shape variation of bubbles formed in polyacrylamide (PAM) aqueous solutions under various conditions was predicted numerically. The practical formation of bubbles was real-time visualized and recorded by a CCD camera and a computer by means of a special laser image measurement system. Results show that the predicted shapes of the bubbles by the present model agree well with experimental observation.展开更多
针对斯特林发动机小负荷燃油雾化不良问题,提出了基于鼓泡-引射耦合的雾化方式.基于VOF(Volume of Fluid)仿真研究了鼓泡喷嘴内气液流态,并依据时间线性稳定性分析,对射流液膜失稳和破碎进行数学描述,建立了鼓泡-引射耦合下的初次雾化模...针对斯特林发动机小负荷燃油雾化不良问题,提出了基于鼓泡-引射耦合的雾化方式.基于VOF(Volume of Fluid)仿真研究了鼓泡喷嘴内气液流态,并依据时间线性稳定性分析,对射流液膜失稳和破碎进行数学描述,建立了鼓泡-引射耦合下的初次雾化模型.分析了气液质量比RGL(gas-liquid mass ratio)、负荷对初次雾化的影响,并与传统雾化方式比较.结果表明:增大RGL会促进射流失稳、减小液滴粒径.相较于传统雾化方式,鼓泡-引射耦合下小负荷索特平均直径SMD减小约62%,雾化质量显著提高.展开更多
In this study,the effect of ethanol addition into pure water and its concentration on bubble diameter,gas hold-up andflow regimes were investigated in an airlift reactor.Air and water with ethanol(concentration ranging...In this study,the effect of ethanol addition into pure water and its concentration on bubble diameter,gas hold-up andflow regimes were investigated in an airlift reactor.Air and water with ethanol(concentration ranging from 0%–1%,v/v)were as dispersed and continuous phases,respectively.Superficial gas velocity was consid-ered as an effective parameter.Bubble size distribution was measured by photography and picture analysis at various concentrations of ethanol and various velocities of gas.Alcohol concentration enhancement caused bubble dia-meter to decrease.Furthermore,the bubbles diameter in pure water was nearly 4 times higher than that of ethanol with concentration of 1%(v/v)and also was 3.4 times higher than that of ethanol with concentration of 0.25%(v/v)at the highest aeration gas velocity inlet.For ethanol solutions in lower superficial gas velocity,a homogenousflow regime was observed.This trend continued to inlet gas velocity of about 0.4 cm/s.The transitionflow regime occurred after this datum although in pure water,a homogenousflow regime was observed up to a superficial gas velocity of 0.7 cm/s.The gas hold-up in dilute ethanol solutions were more than(around 2 times)that of pure water and increased with increasing concentration of ethanol in those solutions.展开更多
Bubbling to Jetting Transition is of the outmost importance in metallurgical processes given that the flow regime influences the refining rates, the refractory erosion, and the blockage of injection nozzles. Bubbling ...Bubbling to Jetting Transition is of the outmost importance in metallurgical processes given that the flow regime influences the refining rates, the refractory erosion, and the blockage of injection nozzles. Bubbling to jetting transition during subsonic bottom injection of argon in molten steel is studied here. The effect of the molten steel height, the injection velocity, the nozzle diameter, and the molten steel viscosity on the jet height and the bubbling to jetting transition is numerically analyzed using Computational Fluid Dynamics. Five subsonic argon injection velocities are considered: 5, 25, 50, 100 and 150 m/s. Three values of the metal height are taken into account, namely 1.5 m, 2 m and 2.5 m. Besides, three values of the nozzle diameters are considered: 0.001 m, 0.005 m and 0.01 m. Finally, three values of the molten steel viscosity are supposed: 0.0067, 0.1 and 1 kg/(m<span style="font-family:Verdana;"><span style="white-space:nowrap;">·</span></span><span style="font-family:Verdana;">s). It is observed that for the argon-molten steel system</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> the bubbling to jetting transition occurs for an injection velocity less than 25 m/s and that for the range of viscosities considered, the molten steel viscosity does not exert significant influence on the jet height and the bubbling to jetting transition. Due to the jet instability at subsonic velocities</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> a second transition, namely jetting to bubbling, is appreciated</span><span style="font-family:Verdana;">.</span>展开更多
Micro-interface intensified reactor(MIR)can be applied in series/parallel in the absorption of CO_(2)in industrial gases by Na_(2)CO_(3)due to the ability to produce large numbers of stable microbubbles.This work focu...Micro-interface intensified reactor(MIR)can be applied in series/parallel in the absorption of CO_(2)in industrial gases by Na_(2)CO_(3)due to the ability to produce large numbers of stable microbubbles.This work focuses on the variation pattern of mass transfer characteristics parameters of the reaction gas in Na_(2)CO_(3) solution under the influence of different solution properties and operating parameters in the reaction of CO_(2)absorption by Na2CO3.The mass transfer characteristics parameters include bubble Sauter mean diameter,gas holdup,interfacial area,liquid side mass transfer coefficient,and liquid side volume mass transfer coefficient kLa.The solution properties and operating parameters include Na2CO3 concentration(0.05–2.0 mol·L^(-1)),superficial gas velocity(0.00221–0.01989 m·s^(-1)),superficial liquid velocity(0.00332–0.02984 m·s^(-1)),and ionic strength(1.42456–1.59588 mol·kg^(-1)).And volumetric mass transfer coeffi-cients kLa and superficial reaction rates r of the MIR and the bubble column reactor are compared in the reaction of sodium carbonate absorption of carbon dioxide,and the former shows a greater improvement under different solution properties and operating parameters.The enhanced role of MIR in mass transfer in non-homogeneous reactions is verified and the feasibility of industrial practical applications of MIR is demonstrated.展开更多
基金Supported by the National Nature Science Foundation of China.
文摘1 INTRODUCTIONBubble diameter distribution and gas holdup are very important parameters indicatingthe characteristics of gas-liquid dispersion,works done are mostly experimentalobservation.Theoretical analysis of bubble diameter has been mostly focused on thebreak-up of bubbles in the impeller region,and only the theoretical relationship be-tween bubble diameter and operating variables in the impeller region has been
文摘Adaptive neuro fuzzy inference system (ANFIS) procedure and regression methods were used to predict the Sauter mean bubble (bubble diameter) and surface area flux of the bubble in a flotation process. The operational conditions of flotation, impeller peripheral speed, superficial gas velocity, and weight percent solids were used as inputs of methods. By using the mentioned operational conditions, the non linear regression results showed that Sauter mean, and surface area flux of the bubble are predictable variables, where the coefficients of determination (R 2 ) are 0.57 and 0.74, respectively. To increase the accuracy of prediction an ANFIS model with cluster radius of 0.4 was applied. ANFIS model was capable of estimating both Sauter mean, and surface area flux of the bubble, where in a testing stage, satisfactory correlations, R 2 = 0.78, and 0.86, were achieved for Sauter mean, and surface area flux of bubble, respectively. Results show that the proposed ANFIS model can accurately estimate outputs and be used in order to predict the parameters without having to conduct the new experiments in a laboratory.
基金Project(2013BAB14B05)supported by National Key Technology Research and Development Program of the Ministry of Science and Technology of China
文摘The properties and thickness of the bubbles in the froth control the flotation process. There is no work showing how to measure bubble film composition and thickness by a straightforward manner. In this work, a novel approach, a custom-designed bubble cell associated with layer interferometry(in the UV-vis region) and FT-IR spectroscopy was used to investigate the effect of solid particle type(hydrophilic vs hydrophobic), concentration and bubble diameter on stability of a bubble blown in air. Stability was quantified by measuring bubble lifetime and hydrated film thickness. Kerosene with silicone oil as a foaming agent was used to evaluate the impact of bubble diameter(test series I). Frother solutions(MIBC, Dowfroth 250, Hexanol and F-150) were used for the solid type concentration experiments(test series II). In the first series of experiments, it was determined that as the diameter of a bubble increased from 10 to 25 mm, so did the hydrated film thickness from 350 to 1000 nm. In the second series, as the silica concentration increased(0 to 10%), an increase in bubble lifetime and hydrated film thickness was resulted(130%-250%). An impact of solid hydrophobicity was found but to a lesser degree than expected. It is possible that the small particle size(<0.1 m) of silica was responsible for this behavior. The findings are used to interpret the effect of solids in flotation froth.
文摘Xenon was used as the gas phase to investigate the hydrodynamic characteristics in a bubble column.It was found that the flow pattern is mainly in the churn-turbulent flow regime through analysing the relationship between the slip velocity and gas holdup.The influence of operating conditions on the gas holdup and the Sauter mean diameter was studied.The experimental results show that the Sauter mean diameter decreases with the increase of energy dissipation rate.A new correlation was developed to predict the Sauter mean diameter with an average error of less than 15%.
基金the National Natural Science Foundation of China(Grant No.51576116)the National Natural Science Foundation of Shandong Province(Grant No.ZR2019MEE041)。
文摘Experiments on subcooled flow boiling have been conducted using water in a rectangular flow channel.Similar to the coolant channel in internal combustion engines(IC engines),the flow channel in this experiment was asymmetrically heated.Bubble images were captured using a high speed camera from the side view of the channel.The experimental conditions in terms of bulk temperature,bulk velocity,pressure and heat flux ranged from 65°C–75°C,0.25 m/s–0.75 m/s,1–1.7 bar and 490 kW/m2–700 kW/m2,respectively.On the basis of these tests,a statistical analysis of the bubble size has been conducted considering a population of 1400 samples.It has been found that the mean Sauter bubble diameter increases with the decrease of subcooling,bulk velocity,pressure and increased heat flux.A modified correlation has been finally proposed to predict the mean Sauter bubble diameter under subcooled flow boiling conditions upstream of the onset of significant void,which shows good accuracy with the experimental results.
文摘The flow behavior of gas and solid was investigated in FCC simulator of φ710×4000/φ870×11000mm.The axial and radial distributions were detected with matrix fiber-opticprobes.It was found that the distribution of bubble diameter in the turbulent region of the fluidizedbed of fine particles was different from the results reported for lab-scale experiments.Radially therewere three areas,i.e.,the central(r/R=0-0.4),the intermittent or stable(r/R=0.4-0.8)and thenear wall(r/R=0.8-1.0)areas respectively.It was noticed that bubbles were almost non-existing atthe near wall area.Hence,according to the coalescence and splitting theory of bubbles,a two-areamodel of bubble diameter distribution was proposed and a dimensionless parameter(γ_M)regarded asan index for’quality’of fluidization was deduced.
基金Supported by National Natural Science Foundation of China (No.20476073)National Programme of Introducing Talents of Discipline to Universities (No.B06006).
文摘Based on the comprehensive forces balance model, a modified model of the formation of a single bub-ble in non-Newtonian fluid under constant flowrate was developed by taking account of the effect of the ingoing gas through orifice as well as its variation on the radial expansion of bubble. The modified model involves the radial expansion equation of bubble surface and the forces balance equation in vertical direction of the bubble respec-tively. The shape variation of bubbles formed in polyacrylamide (PAM) aqueous solutions under various conditions was predicted numerically. The practical formation of bubbles was real-time visualized and recorded by a CCD camera and a computer by means of a special laser image measurement system. Results show that the predicted shapes of the bubbles by the present model agree well with experimental observation.
基金National Natural Science Foundation of China(No.51906262)Natural Science Foundation of Hunan Province,China(No.2020JJ5735)Youth Excellent Sci-Tech Talents Training Plan under Hunan Provincial Sci-Tech Talents Sponsorship Program,China(No.2023TJ-N10)。
文摘针对斯特林发动机小负荷燃油雾化不良问题,提出了基于鼓泡-引射耦合的雾化方式.基于VOF(Volume of Fluid)仿真研究了鼓泡喷嘴内气液流态,并依据时间线性稳定性分析,对射流液膜失稳和破碎进行数学描述,建立了鼓泡-引射耦合下的初次雾化模型.分析了气液质量比RGL(gas-liquid mass ratio)、负荷对初次雾化的影响,并与传统雾化方式比较.结果表明:增大RGL会促进射流失稳、减小液滴粒径.相较于传统雾化方式,鼓泡-引射耦合下小负荷索特平均直径SMD减小约62%,雾化质量显著提高.
基金Arak University for facilities preparation and financial support.
文摘In this study,the effect of ethanol addition into pure water and its concentration on bubble diameter,gas hold-up andflow regimes were investigated in an airlift reactor.Air and water with ethanol(concentration ranging from 0%–1%,v/v)were as dispersed and continuous phases,respectively.Superficial gas velocity was consid-ered as an effective parameter.Bubble size distribution was measured by photography and picture analysis at various concentrations of ethanol and various velocities of gas.Alcohol concentration enhancement caused bubble dia-meter to decrease.Furthermore,the bubbles diameter in pure water was nearly 4 times higher than that of ethanol with concentration of 1%(v/v)and also was 3.4 times higher than that of ethanol with concentration of 0.25%(v/v)at the highest aeration gas velocity inlet.For ethanol solutions in lower superficial gas velocity,a homogenousflow regime was observed.This trend continued to inlet gas velocity of about 0.4 cm/s.The transitionflow regime occurred after this datum although in pure water,a homogenousflow regime was observed up to a superficial gas velocity of 0.7 cm/s.The gas hold-up in dilute ethanol solutions were more than(around 2 times)that of pure water and increased with increasing concentration of ethanol in those solutions.
文摘Bubbling to Jetting Transition is of the outmost importance in metallurgical processes given that the flow regime influences the refining rates, the refractory erosion, and the blockage of injection nozzles. Bubbling to jetting transition during subsonic bottom injection of argon in molten steel is studied here. The effect of the molten steel height, the injection velocity, the nozzle diameter, and the molten steel viscosity on the jet height and the bubbling to jetting transition is numerically analyzed using Computational Fluid Dynamics. Five subsonic argon injection velocities are considered: 5, 25, 50, 100 and 150 m/s. Three values of the metal height are taken into account, namely 1.5 m, 2 m and 2.5 m. Besides, three values of the nozzle diameters are considered: 0.001 m, 0.005 m and 0.01 m. Finally, three values of the molten steel viscosity are supposed: 0.0067, 0.1 and 1 kg/(m<span style="font-family:Verdana;"><span style="white-space:nowrap;">·</span></span><span style="font-family:Verdana;">s). It is observed that for the argon-molten steel system</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> the bubbling to jetting transition occurs for an injection velocity less than 25 m/s and that for the range of viscosities considered, the molten steel viscosity does not exert significant influence on the jet height and the bubbling to jetting transition. Due to the jet instability at subsonic velocities</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> a second transition, namely jetting to bubbling, is appreciated</span><span style="font-family:Verdana;">.</span>
基金Natural Science Foundation of Jiangsu Province(BK20210185)National Natural Science Foundation of China(22278202).
文摘Micro-interface intensified reactor(MIR)can be applied in series/parallel in the absorption of CO_(2)in industrial gases by Na_(2)CO_(3)due to the ability to produce large numbers of stable microbubbles.This work focuses on the variation pattern of mass transfer characteristics parameters of the reaction gas in Na_(2)CO_(3) solution under the influence of different solution properties and operating parameters in the reaction of CO_(2)absorption by Na2CO3.The mass transfer characteristics parameters include bubble Sauter mean diameter,gas holdup,interfacial area,liquid side mass transfer coefficient,and liquid side volume mass transfer coefficient kLa.The solution properties and operating parameters include Na2CO3 concentration(0.05–2.0 mol·L^(-1)),superficial gas velocity(0.00221–0.01989 m·s^(-1)),superficial liquid velocity(0.00332–0.02984 m·s^(-1)),and ionic strength(1.42456–1.59588 mol·kg^(-1)).And volumetric mass transfer coeffi-cients kLa and superficial reaction rates r of the MIR and the bubble column reactor are compared in the reaction of sodium carbonate absorption of carbon dioxide,and the former shows a greater improvement under different solution properties and operating parameters.The enhanced role of MIR in mass transfer in non-homogeneous reactions is verified and the feasibility of industrial practical applications of MIR is demonstrated.