Solutions for radial flow of a Bingham fluid are analyzed in this paper.It aims to eliminate confusions in the literature concerning the plug flow region in different solutions for analysis and design of grouting in r...Solutions for radial flow of a Bingham fluid are analyzed in this paper.It aims to eliminate confusions in the literature concerning the plug flow region in different solutions for analysis and design of grouting in rock fractures.The analyses based on the force balance equation reveal that the plug flow region in Bingham radial flow is independent of the fracture radius,and is not a growth function adapted from the solution of one-dimensional(1D)slit flow according to‘similarity’.Based on the shear stress distribution,we analytically proposed that a non-uniform plug flow region cannot exist.The Bingham fluid(grout)penetration and flowrate evolution as functions of grouting time are given using the correct expression for the plug flow region.The radius-independent plug flow region and the presented flowrate evolution equation are also verified numerically.For radial flow,the relative penetration length is equal to the relative width of plug flow region,which is the same as that for 1D channel flow.Discrepancies in analytical solutions for grout penetration and flowrate evolution were also illustrated.The clarification of the plug flow region and evaluation of discrepancies in analytical solutions presented in this work could simplify modeling and design of grouting in rock engineering applications.展开更多
According to the observational data of viscous debris flows with hyper-concentration, debris flows can be classified into three types:high-viscous, viscous, and sub-viscous debris flows.Distinct formation mechanism of...According to the observational data of viscous debris flows with hyper-concentration, debris flows can be classified into three types:high-viscous, viscous, and sub-viscous debris flows.Distinct formation mechanism of different graded bedding structures in deposits of viscous debris flows was analyzed in this paper by using their yield-stress ratio and flow plug ratio.This paper specially analyzed the effect of Weissenberg which the gravels in squirm condition of hyper-concentration viscous flows would tend to move vertically, and the formation mechanism of the gravels accumulated at surface was also studied.The analysis in this paper can establish a foundation for the studies on differentiation of bedding structures of debris flow deposits and studies on dynamic parameters of debris flows.展开更多
Residence time distribution (RTD) analysis of liquid phase was conducted in an internal airlift loop reactor (AL) and a bubble column (BC) with the tracer response technique. These data were simulated and compared thr...Residence time distribution (RTD) analysis of liquid phase was conducted in an internal airlift loop reactor (AL) and a bubble column (BC) with the tracer response technique. These data were simulated and compared through several flow mixing models. The modeling results of two-parameter model indicated that there were higher ratio of full mixing zones and lower ratio of bypass flow in AL than in BC. Then a completely mixed-plug flow parallel combined (four-parameter) model was established. Modeling results show that it is more precise and more obvious than two-parameter model.展开更多
The transport of liquid plugs in microchannels is very important for many applications such as in medical treatments in airways and in extraction of oil from porous rocks.A plug of wetting and non-wetting liquids driv...The transport of liquid plugs in microchannels is very important for many applications such as in medical treatments in airways and in extraction of oil from porous rocks.A plug of wetting and non-wetting liquids driven by a constant pressure difference through a T-shaped microchannel is studied numerically with lattice Boltzmann(LB) method.A two-phase flow LB model based on field mediators is built.Three typical flow patterns(blocking,rupture and splitting flow) of plug flow are obtained with different driving pressures.It is found that it becomes difficult for a plug with short initial plug length to leave the microchannel;the flow pattern of plug transport varies with the contact angle,especially from wetting to nonwetting;with the increase of interfacial tension,the front interface of plug moves faster;the front and rear interfaces of the plug with small viscosity ratio move faster in the microchannel than those of the plug with large viscosity ratio.The study is helpful to provide theoretical data for the design and scale-up of liquid-liquid reactors and separators.展开更多
Process scale-up remains a considerable challenge for environmental applications of non-thermal plasmas.Undersanding the impact of reactor hydrodynamics in the performance of the process is a key step to overcome this...Process scale-up remains a considerable challenge for environmental applications of non-thermal plasmas.Undersanding the impact of reactor hydrodynamics in the performance of the process is a key step to overcome this challenge.In this work,we apply chemical engineering concepts to analyse the impact that different non-thermal plasma reactor configurations and regimes,such as laminar or plug flow,may have on the reactor performance.We do this in the particular context of the removal of pollutants by non-thermal plasmas,for which a simplified model is available.We generalise this model to different reactor configurations and,under certain hypotheses,we show that a reactor in the laminar regime may have a behaviour significantly different from one in the plug flow regime,often assumed in the non-thermal plasma literature.On the other hand,we show that a packed-bed reactor behaves very similarly to one in the plug flow regime.Beyond those results,the reader will find in this work a quick introduction to chemical reaction engineering concepts.展开更多
Aerosol deposition from the plug laminar flow regime in a circular tube due to diffusion and thermophoresis is studied theoretically, and the aerosol concentration, mean concentration or deposition efficiency, and She...Aerosol deposition from the plug laminar flow regime in a circular tube due to diffusion and thermophoresis is studied theoretically, and the aerosol concentration, mean concentration or deposition efficiency, and Sherwood number are calculated and analyzed by using the analytical solutions based on the detailed comparison with the previous studies. The results show that aerosol concentration distributions for both mechanisms of individual diffusion and combined consideration of diffusion and thermophoresis are symmetrical. However, the axial concentration for the case of diffusion alone is maximal, the maximal values for deposition parameter larger than zero, which appears in the region of non-dimensional radial coordinate from 0 to 1. The large influence of thermophoresis on aerosol mean concentration is found from the detailed comparison, and the bigger of the transport distance and the deposition parameter, the smaller of the aerosol mean concentration. The Sherwood number decreases with the increase of axial coordinate for deposition parameter equal and larger than zero, and the bigger of the deposition parameter, the larger of the deposition velocity.展开更多
To further extend knowledge about fluid film friction in elastohydrodynamic contact,it is important to examine how lubricant flows.In this paper,several film thickness results obtained by interferometry technique for ...To further extend knowledge about fluid film friction in elastohydrodynamic contact,it is important to examine how lubricant flows.In this paper,several film thickness results obtained by interferometry technique for different kinds of experiments were analyzed and discussed based on lubricant flow continuity.Results of two steady-state and two transient experiments are presented.Possible speed profiles that can explain observed film thickness distributions were suggested.It is shown that major part of present experiments can be explained by a single speed profile known as a plug flow.This finding is in contradiction to usual linear speed profile predicted by Reynolds equation.展开更多
NH_(3)has emerged as a promising candidate for low-carbon gas turbines,with NO_(x)emission issues being mitigated by air-staged combustion.However,the role of fuel/air mixing quality(represented by unmixedness)in NO_(...NH_(3)has emerged as a promising candidate for low-carbon gas turbines,with NO_(x)emission issues being mitigated by air-staged combustion.However,the role of fuel/air mixing quality(represented by unmixedness)in NO_(x)formation in NH_(3)systems remains poorly explored.In this study,the characteristics of NO_(x)formation under the effects of unmixedness have been numerically investigated using an NH_(3)/CH_(4)fired air-staged model combustor consisting of perfectly stirred reactors(PSRs)and plug flow reactors(PFRs),employing the 84-species,703-reaction Tian mechanism under H/J heavy duty gas turbine conditions.It was found that a primary-stage equivalence ratio of 1.2–1.5 corresponds to a low NO_(x)formation region under perfectly mixed fuel and air conditions.In this region,a relatively low NO_(x)formation is achieved when the unmixedness is less than 0.12 and NO_(x)formation exhibits low sensitivity to fuel/air unmixedness.Based on these findings and the fact that the air-staged combustion loses its advantage in reducing NO_(x)emissions when the unmixedness exceeds 0.12 across all equivalence ratios,recommended mixing quality thresholds for different equivalence ratios are proposed to guide combustor design and operation optimization.A parametric study of chemical reaction pathways at different unmixedness levels in the two stages demonstrates that NO_(x)is mainly formed in the main combustion zone of the secondary stage via the HNO pathway,which results in NO_(x)formation rising to thousand ppm when unmixedness exceeds 0.3,although NO_(x)reduction through NHi and N_(2)O pathways partially offsets contributions from the HNO and thermal NO_(x)pathways.To leverage the NO_(x)reduction potential of the NHi and N_(2)O pathways,the residence time in both stages should be carefully adjusted to help suppress NO_(x)to as low as 48 ppm.The results of this study are important for engineering applications,providing guidance for the design of NH_(3)fired combustors aimed at significantly reducing NO_(x)formation.展开更多
Solid oxide fuel cell(SOFC)is an extremely promising technology for sustainable energy conversion and storage through highly efficient electrochemical reaction at high-temperature conditions.The existing studies commo...Solid oxide fuel cell(SOFC)is an extremely promising technology for sustainable energy conversion and storage through highly efficient electrochemical reaction at high-temperature conditions.The existing studies commonly address the final equilibrium state of the SOFC electrode reactions,giving less consideration to the micro kinetic of electrode reactions.In this paper,a kinetic model-based SOFC combined cycle power generation system is suggested to recover multiple waste heat,which includes a Kalina cycle(KC)as the bottom cycle and a Rankine cycle(RC)as the top cycle.In devneloping the proposed system,a novel kinetic model is presented for SOFC based on the microscopic mechanism of the oxygen reduction.A dynamic stochastic programming model is established to optimize the integrated system sequentially and simultaneously,with maximum power generation taken as the objective,depending on whether the SOFC system and the KC-RC system are simultaneously optimized.In sequential optimization,the output power of SOFC-KC-RC system is 320.56 kW and it is 415.04 kW using simultaneous optimization,achieving a 29.5%increase in power generation.Further comparison with the previous reports obtained by a thermodynamic model,this work leads to a 10.8%increase in power generation,showing the promising power production performance of the developed system.展开更多
This study presents the use of a new chemical reactor network(CRN) model and non-uniform injectors to predict the NOx emission pollutant in gas turbine combustor. The CRN uses information from Computational Fluid Dyna...This study presents the use of a new chemical reactor network(CRN) model and non-uniform injectors to predict the NOx emission pollutant in gas turbine combustor. The CRN uses information from Computational Fluid Dynamics(CFD) combustion analysis with two injectors of CH4-air mixture. The injectors of CH4-air mixture have different lean equivalence ratio, and they control fuel flow to stabilize combustion and adjust combustor's equivalence ratio. Non-uniform injector is applied to improve the burning process of the turbine combustor. The results of the new CRN for NOx prediction in the gas turbine combustor show very good agreement with the experimental data from Korea Electric Power Research Institute.展开更多
基金funding for this study is provided by the BeFo Rock Engineering Research Foundation(Grant No.392)。
文摘Solutions for radial flow of a Bingham fluid are analyzed in this paper.It aims to eliminate confusions in the literature concerning the plug flow region in different solutions for analysis and design of grouting in rock fractures.The analyses based on the force balance equation reveal that the plug flow region in Bingham radial flow is independent of the fracture radius,and is not a growth function adapted from the solution of one-dimensional(1D)slit flow according to‘similarity’.Based on the shear stress distribution,we analytically proposed that a non-uniform plug flow region cannot exist.The Bingham fluid(grout)penetration and flowrate evolution as functions of grouting time are given using the correct expression for the plug flow region.The radius-independent plug flow region and the presented flowrate evolution equation are also verified numerically.For radial flow,the relative penetration length is equal to the relative width of plug flow region,which is the same as that for 1D channel flow.Discrepancies in analytical solutions for grout penetration and flowrate evolution were also illustrated.The clarification of the plug flow region and evaluation of discrepancies in analytical solutions presented in this work could simplify modeling and design of grouting in rock engineering applications.
基金supported by the National Natural Science Foundation of China (Grant No.40671026)
文摘According to the observational data of viscous debris flows with hyper-concentration, debris flows can be classified into three types:high-viscous, viscous, and sub-viscous debris flows.Distinct formation mechanism of different graded bedding structures in deposits of viscous debris flows was analyzed in this paper by using their yield-stress ratio and flow plug ratio.This paper specially analyzed the effect of Weissenberg which the gravels in squirm condition of hyper-concentration viscous flows would tend to move vertically, and the formation mechanism of the gravels accumulated at surface was also studied.The analysis in this paper can establish a foundation for the studies on differentiation of bedding structures of debris flow deposits and studies on dynamic parameters of debris flows.
文摘Residence time distribution (RTD) analysis of liquid phase was conducted in an internal airlift loop reactor (AL) and a bubble column (BC) with the tracer response technique. These data were simulated and compared through several flow mixing models. The modeling results of two-parameter model indicated that there were higher ratio of full mixing zones and lower ratio of bypass flow in AL than in BC. Then a completely mixed-plug flow parallel combined (four-parameter) model was established. Modeling results show that it is more precise and more obvious than two-parameter model.
基金Supported by the National Basic Research Program of China（2012CB224806）the National Natural Science Foundation of China（20990224,21276256）+1 种基金the National Natural Science Fund for Distinguished Young Scholars（21025627）the National High Technology Research and Development Program of China（2012AA03A606）
文摘The transport of liquid plugs in microchannels is very important for many applications such as in medical treatments in airways and in extraction of oil from porous rocks.A plug of wetting and non-wetting liquids driven by a constant pressure difference through a T-shaped microchannel is studied numerically with lattice Boltzmann(LB) method.A two-phase flow LB model based on field mediators is built.Three typical flow patterns(blocking,rupture and splitting flow) of plug flow are obtained with different driving pressures.It is found that it becomes difficult for a plug with short initial plug length to leave the microchannel;the flow pattern of plug transport varies with the contact angle,especially from wetting to nonwetting;with the increase of interfacial tension,the front interface of plug moves faster;the front and rear interfaces of the plug with small viscosity ratio move faster in the microchannel than those of the plug with large viscosity ratio.The study is helpful to provide theoretical data for the design and scale-up of liquid-liquid reactors and separators.
文摘Process scale-up remains a considerable challenge for environmental applications of non-thermal plasmas.Undersanding the impact of reactor hydrodynamics in the performance of the process is a key step to overcome this challenge.In this work,we apply chemical engineering concepts to analyse the impact that different non-thermal plasma reactor configurations and regimes,such as laminar or plug flow,may have on the reactor performance.We do this in the particular context of the removal of pollutants by non-thermal plasmas,for which a simplified model is available.We generalise this model to different reactor configurations and,under certain hypotheses,we show that a reactor in the laminar regime may have a behaviour significantly different from one in the plug flow regime,often assumed in the non-thermal plasma literature.On the other hand,we show that a packed-bed reactor behaves very similarly to one in the plug flow regime.Beyond those results,the reader will find in this work a quick introduction to chemical reaction engineering concepts.
基金supported by the Scientific Research Program of Ningxia High Education Institution(grant No.NYG2024200)Natural Science Foundation of Ningxia,China(grant Nos.2021AAC03241,2023AAC03045)First-Class Discipline(Pedagogy)Construction Program of Ningxia High Education Institution(grant No.NXYLXK2021B10).
文摘Aerosol deposition from the plug laminar flow regime in a circular tube due to diffusion and thermophoresis is studied theoretically, and the aerosol concentration, mean concentration or deposition efficiency, and Sherwood number are calculated and analyzed by using the analytical solutions based on the detailed comparison with the previous studies. The results show that aerosol concentration distributions for both mechanisms of individual diffusion and combined consideration of diffusion and thermophoresis are symmetrical. However, the axial concentration for the case of diffusion alone is maximal, the maximal values for deposition parameter larger than zero, which appears in the region of non-dimensional radial coordinate from 0 to 1. The large influence of thermophoresis on aerosol mean concentration is found from the detailed comparison, and the bigger of the transport distance and the deposition parameter, the smaller of the aerosol mean concentration. The Sherwood number decreases with the increase of axial coordinate for deposition parameter equal and larger than zero, and the bigger of the deposition parameter, the larger of the deposition velocity.
文摘To further extend knowledge about fluid film friction in elastohydrodynamic contact,it is important to examine how lubricant flows.In this paper,several film thickness results obtained by interferometry technique for different kinds of experiments were analyzed and discussed based on lubricant flow continuity.Results of two steady-state and two transient experiments are presented.Possible speed profiles that can explain observed film thickness distributions were suggested.It is shown that major part of present experiments can be explained by a single speed profile known as a plug flow.This finding is in contradiction to usual linear speed profile predicted by Reynolds equation.
基金supported by China Aeroengine University—Industry Joint R&D Projects(Grant No.HFZL2023CXY031).
文摘NH_(3)has emerged as a promising candidate for low-carbon gas turbines,with NO_(x)emission issues being mitigated by air-staged combustion.However,the role of fuel/air mixing quality(represented by unmixedness)in NO_(x)formation in NH_(3)systems remains poorly explored.In this study,the characteristics of NO_(x)formation under the effects of unmixedness have been numerically investigated using an NH_(3)/CH_(4)fired air-staged model combustor consisting of perfectly stirred reactors(PSRs)and plug flow reactors(PFRs),employing the 84-species,703-reaction Tian mechanism under H/J heavy duty gas turbine conditions.It was found that a primary-stage equivalence ratio of 1.2–1.5 corresponds to a low NO_(x)formation region under perfectly mixed fuel and air conditions.In this region,a relatively low NO_(x)formation is achieved when the unmixedness is less than 0.12 and NO_(x)formation exhibits low sensitivity to fuel/air unmixedness.Based on these findings and the fact that the air-staged combustion loses its advantage in reducing NO_(x)emissions when the unmixedness exceeds 0.12 across all equivalence ratios,recommended mixing quality thresholds for different equivalence ratios are proposed to guide combustor design and operation optimization.A parametric study of chemical reaction pathways at different unmixedness levels in the two stages demonstrates that NO_(x)is mainly formed in the main combustion zone of the secondary stage via the HNO pathway,which results in NO_(x)formation rising to thousand ppm when unmixedness exceeds 0.3,although NO_(x)reduction through NHi and N_(2)O pathways partially offsets contributions from the HNO and thermal NO_(x)pathways.To leverage the NO_(x)reduction potential of the NHi and N_(2)O pathways,the residence time in both stages should be carefully adjusted to help suppress NO_(x)to as low as 48 ppm.The results of this study are important for engineering applications,providing guidance for the design of NH_(3)fired combustors aimed at significantly reducing NO_(x)formation.
基金supported by the financial support provided by the National Natural Science Foundation of China(Grant Nos.22008023,and 22178045)Fundamental Research Funds for the Central Universities(Grant No.DUT21RC(3)109).
文摘Solid oxide fuel cell(SOFC)is an extremely promising technology for sustainable energy conversion and storage through highly efficient electrochemical reaction at high-temperature conditions.The existing studies commonly address the final equilibrium state of the SOFC electrode reactions,giving less consideration to the micro kinetic of electrode reactions.In this paper,a kinetic model-based SOFC combined cycle power generation system is suggested to recover multiple waste heat,which includes a Kalina cycle(KC)as the bottom cycle and a Rankine cycle(RC)as the top cycle.In devneloping the proposed system,a novel kinetic model is presented for SOFC based on the microscopic mechanism of the oxygen reduction.A dynamic stochastic programming model is established to optimize the integrated system sequentially and simultaneously,with maximum power generation taken as the objective,depending on whether the SOFC system and the KC-RC system are simultaneously optimized.In sequential optimization,the output power of SOFC-KC-RC system is 320.56 kW and it is 415.04 kW using simultaneous optimization,achieving a 29.5%increase in power generation.Further comparison with the previous reports obtained by a thermodynamic model,this work leads to a 10.8%increase in power generation,showing the promising power production performance of the developed system.
基金supported by Research Program supported by Konkuk University, Korea, 2010
文摘This study presents the use of a new chemical reactor network(CRN) model and non-uniform injectors to predict the NOx emission pollutant in gas turbine combustor. The CRN uses information from Computational Fluid Dynamics(CFD) combustion analysis with two injectors of CH4-air mixture. The injectors of CH4-air mixture have different lean equivalence ratio, and they control fuel flow to stabilize combustion and adjust combustor's equivalence ratio. Non-uniform injector is applied to improve the burning process of the turbine combustor. The results of the new CRN for NOx prediction in the gas turbine combustor show very good agreement with the experimental data from Korea Electric Power Research Institute.
