Electrochemical impedance spectroscopy(EIS)is a robust characterization method to probe prevalent(electro)chemical processes in an electrochemical system.Despite its extensive utilization in fuel cell research,the app...Electrochemical impedance spectroscopy(EIS)is a robust characterization method to probe prevalent(electro)chemical processes in an electrochemical system.Despite its extensive utilization in fuel cell research,the application of EIS in redox flow battery systems particularly for simplified two-electrode full-cell configurations is more limited.Herein we attempt to strengthen the understa nding of cha racteristic EIS data of vanadium redox flow batteries by a combination of equivalent circuit modeling with a validated Multiphysics model analyzed under hydrodynamic conditions in frequency domain.Following a highlight of system linearity and stability concerns for EIS in redox flow batteries,we specifically use our combinatory approach to investigate the effects of different cell component properties on observed galva nostatic EIS spectra and accompanying fitted equivalent circuit element parameters.For the investigated two-electrode full-cell flow battery configuration with the same electrode material on both sides,the EIS spectral data is observed to be dominated by different mass or cha rge transport processes at different ends of the spectrum.Sensitivity analyses of both obtained EIS spectral data and fitted circuit elements parameters show that electrode morphological properties,membrane porosity,and electrolyte inflow conditions predominantly define the EIS spectral data.Insights from the type of analyses performed herein can facilitate flow battery cell/stack diagnostics and targeted performance improvement efforts.展开更多
Upgrades to power systems and the rapid growth of electric vehicles significantly heighten the importance of lithium-ion batteries(LiBs)in energy systems.As a complex dynamic system;the charging and discharging process...Upgrades to power systems and the rapid growth of electric vehicles significantly heighten the importance of lithium-ion batteries(LiBs)in energy systems.As a complex dynamic system;the charging and discharging process of LiBs involves the evolution of multiphysicsfields;such as concentration;electricity;and stress.For quantitative analysis of the internal mechanisms of LiBs;as well as the development guidance and performance prediction of high-performance batteries;modeling has advantages that cannot be matched by traditional experimental methods.Major research efforts in the past decades have made significant strides in modeling the internal processes and physicalfield evolution of LiBs.Importantly;the scattered ideas need to be integrated into a structured framework to form a complete LiBs multi-physicalfield model.This work reviews important ad-vances in LiBs modeling from the perspectives of describing the internal processes of the battery and portraying the evolution of the physicalfield.First;quantitative descriptions of the charging and discharging behaviors and the side reactions are reviewed to investigate the battery reaction mechanisms.In addition;the characterization of the evolution of the stress and temperaturefields within the battery as well as the coupling between them and the internal reactions are discussed.Finally;some suggestions for future improvements in the modeling are given;ranging from equation optimization to parameter acquisition and the application of artificial intelligence.It is hoped that this work will facilitate the development of models with sufficient accuracy and efficient computa-tional cost to provide guidance for the improvement of LiBs.展开更多
Silicon monoxide(SiO)(silicon[Si]mixed with silicon dioxide[SiO_(2)])/graphite(Gr)composite material is one of the most commercially promising anode materials for the next generation of high-energy-density lithium-ion...Silicon monoxide(SiO)(silicon[Si]mixed with silicon dioxide[SiO_(2)])/graphite(Gr)composite material is one of the most commercially promising anode materials for the next generation of high-energy-density lithium-ion batteries.The major bottleneck for SiO/Gr composite anode is the poor cyclability arising from the stress/strain behaviors due to the mismatch between two heterogenous materials during the lithiation/delithiation process.To date,a meticulous and quantitative understanding of the highly nonlinear coupling behaviors of such materials is still lacking.Herein,an electro–chemo–mechanics-coupled detailed model containing particle geometries is established.The underlying mechanism of the regulation between SiO and Gr components during electrochemical cycling is quantitatively revealed.We discover that increasing the SiO weight percentage(wt%)reduces the utilization efficiency of the active materials at the same 1C rate charging and enhances the hindering effects of stress-driven flux on diffusion.In addition,the mechanical constraint demonstrates a balanced effect on the overall performance of cells and the local behaviors of particles.This study provides new insights into the fundamental interactions between SiO and Gr materials and advances the investigation methodology for the design and evaluation of next-generation high-energydensity batteries.展开更多
Additive manufacturing of fiber-reinforced polymer composites has garnered great interest due to its potential in fabricating functional products with lightweight characteristics and unique material properties.However...Additive manufacturing of fiber-reinforced polymer composites has garnered great interest due to its potential in fabricating functional products with lightweight characteristics and unique material properties.However,the major concern in polymer composites remains the presence of pore defects,as a thorough understanding of pore formation is insufficient.In this study,a powder-scale multiphysics framework has been developed to simulate the printing process of fiber-reinforced polymer composites in powder bed fusion additive manufacturing.This numerical framework involves various multiphysics phenomena such as particle flow dynamics of fiber-reinforced polymer composite powder,infrared laser–particle interaction,heat transfer,and multiphase fluid flow dynamics.The melt depths of one-layer glass fiber–reinforced polyamide 12 composite parts fabricated by selective laser sintering are measured to validate modelling predictions.The numerical framework is employed to conduct an in-depth investigation of pore formation mechanisms within printed composites.Our simulation results suggest that an increasing fiber weight fraction would lead to a lower densification rate,larger porosity,and lower pore sphericity in the composites.展开更多
Solid-to-solid interfacial issues are one of the most intractable problems hindering the practical application of all-solid-state batteries(ASSBs).The interfacial instability behaviors caused by the rough interface be...Solid-to-solid interfacial issues are one of the most intractable problems hindering the practical application of all-solid-state batteries(ASSBs).The interfacial instability behaviors caused by the rough interface between lithium anode and solid electrolyte(SE)involve complicated electro-chemo-mechanics interplays and their quantitative relationships still remain unclear.The three-dimensional electro-chemomechanical coupled model with randomly generated rough lithium-SE interface is developed in this study to investigate the effects of interface roughness on the interfacial failure behaviors.Results demonstrate that the existence of a rough lithium-SE interface causes the highly concentrated strain,GPa-level stress,and localized current density at the protruding tips,probably inducing dendrite formation and interface cracking.The interface roughness effect is much more pronounced in lithium anode than graphite anode due to their different Li storage mechanisms,i.e.,surface deposition and Li intercalation.Excessive stack pressure(>50 MPa)magnifies the stress effect on overpotential to enlarge the current density localization and deteriorate the interfacial instability issues.Reducing interface roughness through surface treatment,together with regulation of external operation conditions,can effectively improve interfacial stability performance.The results provide an in-depth understanding of the underlying electro-chemo-mechanical coupling mechanism caused by the rough anode-SE interface and bring more insights into further improvement of ASSBs'enhanced reliability and longevity.展开更多
Thermal runaway(TR)in lithium-ion batteries(LIBs)involves a complicated multiphysics process with potentially catastrophic consequences,highlighting the importance of investigating effective prevention strategies.This...Thermal runaway(TR)in lithium-ion batteries(LIBs)involves a complicated multiphysics process with potentially catastrophic consequences,highlighting the importance of investigating effective prevention strategies.This study employs a lumped model integrating electrochemical and decomposition reaction kinetics to predict the evolution of the TR of LIBs triggered by axial nail penetration,validated by experimental tests.A computational fluid dynamics(CFD)-based turbulent flow model is further employed to simulate the thermal runaway propagation(TRP)behavior induced by high-temperature gases within the battery module.A parameterized analysis based on numerical simulation is conducted to quantify the impact of thermal insulation material properties on thermal diffusion and heat accumulation within the module.The results indicate that damage to the battery vent significantly increases the risk of sidewall rupture during TR.The incorporation of thermal barriers is essential in the thermal design of battery modules to prevent heat transfer via convection from the thermal exhaust caused by sidewall rupture to adjacent cells.In addition,a reduction in the thermal diffusivity of the thermal barrier material is required to minimize thermal exchange between battery cells.By adopting insulating materials with thermal diffusivity lower than 0.3 mm^(2)/s,the TRP of batteries can be mitigated under non-enclosed conditions.These findings contribute to improved battery safety and inform the development of more effective thermal protection measures and safety standards.展开更多
Polymeric materials have a broad range of mechanical and physical properties.They have been widely used in material science,biomedical engineering,chemical engineering,and mechanical engineering.The introduction of ac...Polymeric materials have a broad range of mechanical and physical properties.They have been widely used in material science,biomedical engineering,chemical engineering,and mechanical engineering.The introduction of active elements into the soft matrix of polymers has enabled much more diversified functionalities of polymeric materials,such as self-healing,electroactive,magnetosensitive,pH-responsive,and many others.To further enable applications of these multifunctional polymers,a mechanistic modeling method is required and of great significance,as it can provide links between materials’micro/nano-structures and their macroscopic mechanical behaviors.Towards this goal,molecular simulation plays an important role in understanding the deformation and evolution of polymer networks under external loads and stimuli.These molecular insights provide physical guidance in the formulation of mechanistic-based continuum models for multifunctional polymers.In this perspective,we present a molecular simulation-guided and physics-informed modeling framework for polymeric materials.Firstly,the physical theory for polymer chains and their networks is briefly introduced.It serves as the foundation for mechanistic-models of polymers,linking their chemistry,physics,and mechanics together.Secondly,the deformation of the polymer network is used to derive the strain energy density functions.Thus,the corresponding continuum models can capture the intrinsic deformation mechanisms of polymer networks.We then highlight several representative examples across multiphysics coupling problems to describe in detail for this proposed framework.Last but not least,we discuss potential challenges and opportunities in the modeling of multifunctional polymers for future research directions.展开更多
Solid oxide fuel cell(SOFC)is a promising power generation technology with high efficiency and can operate with a wide range of fuels.Although H2 delivery and storage are still hurdles,natural gas is readily accessibl...Solid oxide fuel cell(SOFC)is a promising power generation technology with high efficiency and can operate with a wide range of fuels.Although H2 delivery and storage are still hurdles,natural gas is readily accessible through existing pipeline infrastructure and therefore stands as a viable fuel candidate for SOFC.Owing to the high operating temperature,the methane in natural gas can be directly reformed in the anode of an SOFC.However,mechanical failure remains a critical issue and hinders the prevalence of traditional planar SOFCs.A novel flat-tubular structure with symmetrical double-sided cathodes was previously proposed to improve mechanical durability.In this work,the performance of a methane-fueled SOFC with symmetrical double-sided cathodes is analyzed with a numerical multiphysics model.The distributions of different physical fields in the SOFC are investigated.Special attention is paid to stress analysis,which is closely related to the mechanical stability of an SOFC.Furthermore,the CH_(4)-fueled and H_(2)-fueled SOFCs are also compared in terms of the distribution of thermal stress.A lower first principal stress is observed for CH_(4)-fueled flat-tubular SOFC,demonstrating a reduced probability of mechanical failures and potentially extended lifespan.展开更多
High temperature superconducting homopolar inductor machine(HTS-HIM)is concerned and studied for electric aircraft because of its high power density,high efficiency,and high power-to-weight ratio.In an HTS-HIM,the hig...High temperature superconducting homopolar inductor machine(HTS-HIM)is concerned and studied for electric aircraft because of its high power density,high efficiency,and high power-to-weight ratio.In an HTS-HIM,the high temperature superconducting magnets carrying DC currents under alternating background magnetic fields work as excitation magnets.Under extreme electromagnetic conditions,the voltage,loss,and temperature of the HTS magnets will increase because of the dynamic resistance effect.To predict the behaviors of the HTS magnet,it is necessary to analyze its electromagnetic-thermal characteristics by using a multiphysics model.This paper establishes a 2D axisymmetric multilayer multiphysics HTS magnet model based on the H-formulation.By using this multilayer multiphysics model,the electromagnetic-thermal characteristics of each turn can be analyzed.Meanwhile,this model can not only analyze the total loss and loss components of each layer under various operating conditions but also predict the temperature and quench behaviors of each part.The result shows that the loss components of the REBCO layer have distinct temperature dependence.When considering the thermal field effect,the magnetization loss of the REBCO layer reduces by 75%and the transport loss of the REBCO layer increases by 45%under high direct currents and high AC magnetic fields.Meanwhile,the temperature of the external turn is higher than the internal turn,and the external turn is at risk of quench in the operating process when the direct currents and AC magnetic fields are high.The multilayer multiphysics model is a powerful tool for designing,analyzing,and optimizing the HTS magnets in HTS-HIMs,and this multiphysics modelling technique can be utilized in modelling and simulating HTS REBCO magnets in various applications.展开更多
This work proposes a novel tubular structure of high-temperature proton exchange membrane fuel cell(PEMFC)integrated with a built-in packed-bed methanol steam reformer to provide hydrogen for power output.A two-dimens...This work proposes a novel tubular structure of high-temperature proton exchange membrane fuel cell(PEMFC)integrated with a built-in packed-bed methanol steam reformer to provide hydrogen for power output.A two-dimensional axisymmetric non-isothermal model was developed in COMSOL Multiphysics 5.4 to simulate the performance of a tubular high temperature proton membrane fuel cell and a packed bed methanol reformer.The model considers the coupling multi-physical processes,including methanol reforming reaction,water gas shift reaction,methanol cracking reaction as well as the heat,mass and momentum transport processes.The sub-model of the tubular packed-bed methanol reformer is validated between 433 K and 493 K with the experimental data reported in the literature.The sub-model of the high temperature proton exchange fuel cell is validated between 393 K and 433 K with the published literature.Our results show that power output and temperature distribution of the integrated unit depend on methanol flow rates and working voltages.It was suggested that stable power generation performance of 0.14 W/cm_(2)and temperature drop in methanol steam reformer of≤10 K could be achieved by controlling the methanol space-time ratio of≥250 kg·s/mol with working voltage at 0.6 V,even in the absence of an external heat source.展开更多
Owing to the relatively low stifness of the slide and the considerable deformation under support force,the fuid–structure interaction(FSI)phenomenon in aerostatic slides is generally pronounced.This phenomenon afects...Owing to the relatively low stifness of the slide and the considerable deformation under support force,the fuid–structure interaction(FSI)phenomenon in aerostatic slides is generally pronounced.This phenomenon afects the performance of static pressure slides,particularly those with high load-carrying capacity and low stifness.However,most existing methods for analyzing the efect of FSI on the stifness of static pressure slides are iterative and computationally expensive.To address this issue,a novel direct method is proposed for evaluating the stifness of static pressure slides while considering FSI.This method can quickly and precisely obtain numerical solutions.Furthermore,the accuracy of the proposed method is validated through experiments.Based on the developed FSI model,the efects of normal force and flm thickness on the normal stifness of aerostatic slides are also investigated.展开更多
基金sponsored by the Dubai Electricity and Water Authority(DEWA)R&D centre,Dubai,United Arab Emirates。
文摘Electrochemical impedance spectroscopy(EIS)is a robust characterization method to probe prevalent(electro)chemical processes in an electrochemical system.Despite its extensive utilization in fuel cell research,the application of EIS in redox flow battery systems particularly for simplified two-electrode full-cell configurations is more limited.Herein we attempt to strengthen the understa nding of cha racteristic EIS data of vanadium redox flow batteries by a combination of equivalent circuit modeling with a validated Multiphysics model analyzed under hydrodynamic conditions in frequency domain.Following a highlight of system linearity and stability concerns for EIS in redox flow batteries,we specifically use our combinatory approach to investigate the effects of different cell component properties on observed galva nostatic EIS spectra and accompanying fitted equivalent circuit element parameters.For the investigated two-electrode full-cell flow battery configuration with the same electrode material on both sides,the EIS spectral data is observed to be dominated by different mass or cha rge transport processes at different ends of the spectrum.Sensitivity analyses of both obtained EIS spectral data and fitted circuit elements parameters show that electrode morphological properties,membrane porosity,and electrolyte inflow conditions predominantly define the EIS spectral data.Insights from the type of analyses performed herein can facilitate flow battery cell/stack diagnostics and targeted performance improvement efforts.
基金funding support from National Key R&D Program of China(2023YFB2408100)Chinese Academy of Sciences Project for Young Scientists in Basic Research(YSBR-098)National Innovative Talents Program(GG2090007001).
文摘Upgrades to power systems and the rapid growth of electric vehicles significantly heighten the importance of lithium-ion batteries(LiBs)in energy systems.As a complex dynamic system;the charging and discharging process of LiBs involves the evolution of multiphysicsfields;such as concentration;electricity;and stress.For quantitative analysis of the internal mechanisms of LiBs;as well as the development guidance and performance prediction of high-performance batteries;modeling has advantages that cannot be matched by traditional experimental methods.Major research efforts in the past decades have made significant strides in modeling the internal processes and physicalfield evolution of LiBs.Importantly;the scattered ideas need to be integrated into a structured framework to form a complete LiBs multi-physicalfield model.This work reviews important ad-vances in LiBs modeling from the perspectives of describing the internal processes of the battery and portraying the evolution of the physicalfield.First;quantitative descriptions of the charging and discharging behaviors and the side reactions are reviewed to investigate the battery reaction mechanisms.In addition;the characterization of the evolution of the stress and temperaturefields within the battery as well as the coupling between them and the internal reactions are discussed.Finally;some suggestions for future improvements in the modeling are given;ranging from equation optimization to parameter acquisition and the application of artificial intelligence.It is hoped that this work will facilitate the development of models with sufficient accuracy and efficient computa-tional cost to provide guidance for the improvement of LiBs.
文摘Silicon monoxide(SiO)(silicon[Si]mixed with silicon dioxide[SiO_(2)])/graphite(Gr)composite material is one of the most commercially promising anode materials for the next generation of high-energy-density lithium-ion batteries.The major bottleneck for SiO/Gr composite anode is the poor cyclability arising from the stress/strain behaviors due to the mismatch between two heterogenous materials during the lithiation/delithiation process.To date,a meticulous and quantitative understanding of the highly nonlinear coupling behaviors of such materials is still lacking.Herein,an electro–chemo–mechanics-coupled detailed model containing particle geometries is established.The underlying mechanism of the regulation between SiO and Gr components during electrochemical cycling is quantitatively revealed.We discover that increasing the SiO weight percentage(wt%)reduces the utilization efficiency of the active materials at the same 1C rate charging and enhances the hindering effects of stress-driven flux on diffusion.In addition,the mechanical constraint demonstrates a balanced effect on the overall performance of cells and the local behaviors of particles.This study provides new insights into the fundamental interactions between SiO and Gr materials and advances the investigation methodology for the design and evaluation of next-generation high-energydensity batteries.
基金supported by the RIE2020 Industry Alignment Fund–Industry Collaboration Projects(IAF–ICP)Funding Initiative,Singapore and cash and in-kind contribution from the industry partner,HP Inc.
文摘Additive manufacturing of fiber-reinforced polymer composites has garnered great interest due to its potential in fabricating functional products with lightweight characteristics and unique material properties.However,the major concern in polymer composites remains the presence of pore defects,as a thorough understanding of pore formation is insufficient.In this study,a powder-scale multiphysics framework has been developed to simulate the printing process of fiber-reinforced polymer composites in powder bed fusion additive manufacturing.This numerical framework involves various multiphysics phenomena such as particle flow dynamics of fiber-reinforced polymer composite powder,infrared laser–particle interaction,heat transfer,and multiphase fluid flow dynamics.The melt depths of one-layer glass fiber–reinforced polyamide 12 composite parts fabricated by selective laser sintering are measured to validate modelling predictions.The numerical framework is employed to conduct an in-depth investigation of pore formation mechanisms within printed composites.Our simulation results suggest that an increasing fiber weight fraction would lead to a lower densification rate,larger porosity,and lower pore sphericity in the composites.
基金financial support from National Science Foundation of China(Grant No.52402445)the Natural Science Foundation of Jiangsu Province(Grant No.BK20241325)the startup support from Southeast University(Grant No.RF1028623337)。
文摘Solid-to-solid interfacial issues are one of the most intractable problems hindering the practical application of all-solid-state batteries(ASSBs).The interfacial instability behaviors caused by the rough interface between lithium anode and solid electrolyte(SE)involve complicated electro-chemo-mechanics interplays and their quantitative relationships still remain unclear.The three-dimensional electro-chemomechanical coupled model with randomly generated rough lithium-SE interface is developed in this study to investigate the effects of interface roughness on the interfacial failure behaviors.Results demonstrate that the existence of a rough lithium-SE interface causes the highly concentrated strain,GPa-level stress,and localized current density at the protruding tips,probably inducing dendrite formation and interface cracking.The interface roughness effect is much more pronounced in lithium anode than graphite anode due to their different Li storage mechanisms,i.e.,surface deposition and Li intercalation.Excessive stack pressure(>50 MPa)magnifies the stress effect on overpotential to enlarge the current density localization and deteriorate the interfacial instability issues.Reducing interface roughness through surface treatment,together with regulation of external operation conditions,can effectively improve interfacial stability performance.The results provide an in-depth understanding of the underlying electro-chemo-mechanical coupling mechanism caused by the rough anode-SE interface and bring more insights into further improvement of ASSBs'enhanced reliability and longevity.
基金the Faraday Institution’s SafeBatt(https://www.safebatt.ac.uk/)project[grant numbers:EP/S003053/1,FIRG061]DSIT and the Royal Academy of Engineering,under the Chair in Emerging Technologies Scheme(CiET1718/59)。
文摘Thermal runaway(TR)in lithium-ion batteries(LIBs)involves a complicated multiphysics process with potentially catastrophic consequences,highlighting the importance of investigating effective prevention strategies.This study employs a lumped model integrating electrochemical and decomposition reaction kinetics to predict the evolution of the TR of LIBs triggered by axial nail penetration,validated by experimental tests.A computational fluid dynamics(CFD)-based turbulent flow model is further employed to simulate the thermal runaway propagation(TRP)behavior induced by high-temperature gases within the battery module.A parameterized analysis based on numerical simulation is conducted to quantify the impact of thermal insulation material properties on thermal diffusion and heat accumulation within the module.The results indicate that damage to the battery vent significantly increases the risk of sidewall rupture during TR.The incorporation of thermal barriers is essential in the thermal design of battery modules to prevent heat transfer via convection from the thermal exhaust caused by sidewall rupture to adjacent cells.In addition,a reduction in the thermal diffusivity of the thermal barrier material is required to minimize thermal exchange between battery cells.By adopting insulating materials with thermal diffusivity lower than 0.3 mm^(2)/s,the TRP of batteries can be mitigated under non-enclosed conditions.These findings contribute to improved battery safety and inform the development of more effective thermal protection measures and safety standards.
基金the support from the Interdisciplinary Multi-Investigator Materials Proposals(IMMP)program of the Institute of Materials Science at the University of Connecticutfunding support from the National Science Foundation(CMMI-1762661 and CMMI-1934829)the funding support from the National Science Foundation(CMMI-1762567 and CMMI-1943598).
文摘Polymeric materials have a broad range of mechanical and physical properties.They have been widely used in material science,biomedical engineering,chemical engineering,and mechanical engineering.The introduction of active elements into the soft matrix of polymers has enabled much more diversified functionalities of polymeric materials,such as self-healing,electroactive,magnetosensitive,pH-responsive,and many others.To further enable applications of these multifunctional polymers,a mechanistic modeling method is required and of great significance,as it can provide links between materials’micro/nano-structures and their macroscopic mechanical behaviors.Towards this goal,molecular simulation plays an important role in understanding the deformation and evolution of polymer networks under external loads and stimuli.These molecular insights provide physical guidance in the formulation of mechanistic-based continuum models for multifunctional polymers.In this perspective,we present a molecular simulation-guided and physics-informed modeling framework for polymeric materials.Firstly,the physical theory for polymer chains and their networks is briefly introduced.It serves as the foundation for mechanistic-models of polymers,linking their chemistry,physics,and mechanics together.Secondly,the deformation of the polymer network is used to derive the strain energy density functions.Thus,the corresponding continuum models can capture the intrinsic deformation mechanisms of polymer networks.We then highlight several representative examples across multiphysics coupling problems to describe in detail for this proposed framework.Last but not least,we discuss potential challenges and opportunities in the modeling of multifunctional polymers for future research directions.
基金the National Natural Science Foundation of China(11802106,11932005,U20A20251,52102226,and 22109101)Department of Education of Guangdong Province,China(2021KCXTD006 and 2021KQNCX272)+1 种基金Science,Technology and Innovation Commission of Shenzhen Municipality,China(GJHZ20220913143009017 and JCYJ20210324093008021)Development and Reform Commission of Shenzhen Municipality,China(XMHT20220103004)is appreciated.
文摘Solid oxide fuel cell(SOFC)is a promising power generation technology with high efficiency and can operate with a wide range of fuels.Although H2 delivery and storage are still hurdles,natural gas is readily accessible through existing pipeline infrastructure and therefore stands as a viable fuel candidate for SOFC.Owing to the high operating temperature,the methane in natural gas can be directly reformed in the anode of an SOFC.However,mechanical failure remains a critical issue and hinders the prevalence of traditional planar SOFCs.A novel flat-tubular structure with symmetrical double-sided cathodes was previously proposed to improve mechanical durability.In this work,the performance of a methane-fueled SOFC with symmetrical double-sided cathodes is analyzed with a numerical multiphysics model.The distributions of different physical fields in the SOFC are investigated.Special attention is paid to stress analysis,which is closely related to the mechanical stability of an SOFC.Furthermore,the CH_(4)-fueled and H_(2)-fueled SOFCs are also compared in terms of the distribution of thermal stress.A lower first principal stress is observed for CH_(4)-fueled flat-tubular SOFC,demonstrating a reduced probability of mechanical failures and potentially extended lifespan.
文摘High temperature superconducting homopolar inductor machine(HTS-HIM)is concerned and studied for electric aircraft because of its high power density,high efficiency,and high power-to-weight ratio.In an HTS-HIM,the high temperature superconducting magnets carrying DC currents under alternating background magnetic fields work as excitation magnets.Under extreme electromagnetic conditions,the voltage,loss,and temperature of the HTS magnets will increase because of the dynamic resistance effect.To predict the behaviors of the HTS magnet,it is necessary to analyze its electromagnetic-thermal characteristics by using a multiphysics model.This paper establishes a 2D axisymmetric multilayer multiphysics HTS magnet model based on the H-formulation.By using this multilayer multiphysics model,the electromagnetic-thermal characteristics of each turn can be analyzed.Meanwhile,this model can not only analyze the total loss and loss components of each layer under various operating conditions but also predict the temperature and quench behaviors of each part.The result shows that the loss components of the REBCO layer have distinct temperature dependence.When considering the thermal field effect,the magnetization loss of the REBCO layer reduces by 75%and the transport loss of the REBCO layer increases by 45%under high direct currents and high AC magnetic fields.Meanwhile,the temperature of the external turn is higher than the internal turn,and the external turn is at risk of quench in the operating process when the direct currents and AC magnetic fields are high.The multilayer multiphysics model is a powerful tool for designing,analyzing,and optimizing the HTS magnets in HTS-HIMs,and this multiphysics modelling technique can be utilized in modelling and simulating HTS REBCO magnets in various applications.
文摘This work proposes a novel tubular structure of high-temperature proton exchange membrane fuel cell(PEMFC)integrated with a built-in packed-bed methanol steam reformer to provide hydrogen for power output.A two-dimensional axisymmetric non-isothermal model was developed in COMSOL Multiphysics 5.4 to simulate the performance of a tubular high temperature proton membrane fuel cell and a packed bed methanol reformer.The model considers the coupling multi-physical processes,including methanol reforming reaction,water gas shift reaction,methanol cracking reaction as well as the heat,mass and momentum transport processes.The sub-model of the tubular packed-bed methanol reformer is validated between 433 K and 493 K with the experimental data reported in the literature.The sub-model of the high temperature proton exchange fuel cell is validated between 393 K and 433 K with the published literature.Our results show that power output and temperature distribution of the integrated unit depend on methanol flow rates and working voltages.It was suggested that stable power generation performance of 0.14 W/cm_(2)and temperature drop in methanol steam reformer of≤10 K could be achieved by controlling the methanol space-time ratio of≥250 kg·s/mol with working voltage at 0.6 V,even in the absence of an external heat source.
基金The National Key Research and Development Program of China(2022YFB3402705)The National Natural Science Foundation of China(52105439).
文摘Owing to the relatively low stifness of the slide and the considerable deformation under support force,the fuid–structure interaction(FSI)phenomenon in aerostatic slides is generally pronounced.This phenomenon afects the performance of static pressure slides,particularly those with high load-carrying capacity and low stifness.However,most existing methods for analyzing the efect of FSI on the stifness of static pressure slides are iterative and computationally expensive.To address this issue,a novel direct method is proposed for evaluating the stifness of static pressure slides while considering FSI.This method can quickly and precisely obtain numerical solutions.Furthermore,the accuracy of the proposed method is validated through experiments.Based on the developed FSI model,the efects of normal force and flm thickness on the normal stifness of aerostatic slides are also investigated.
