In this study,we perform a numerical investigation of a steady laminar stagnation flow flame stabilized at a wall with the consideration of heat transport,focusing on a lean hydrogen/air mixture with a fuel/air equiva...In this study,we perform a numerical investigation of a steady laminar stagnation flow flame stabilized at a wall with the consideration of heat transport,focusing on a lean hydrogen/air mixture with a fuel/air equivalence ratio 0.6.We discuss the NO emissions and their formation rates under various conditions,such as flow velocity and combustion pressure.It is found that the predominant reaction pathway for NO formation involves NNH radicals,though this changes near the wall surface.Beyond examining the wall's influence on flame structures,the present work focuses on the impact of combustion process on materials.Specifically,the accumulation of atomic hydrogen at the wall surface is explored,which is significant for the consequent modeling of potential hydrogen embrittlement.Additionally,the growth rate of oxide layers on the material surface increases significantly if the combustion pressure and consequently the combustion temperatures are enhanced.These investigations offer valuable insights into how combustion processes affect material,which is useful for designing engineering components under high-temperature environments.展开更多
Though being an important mechanism in systems involving unsteady fluid flows(e.g.,fluids interacting with moving structures,particles in turbulent flows,turbulent flame propagation),the memory effect is usually not c...Though being an important mechanism in systems involving unsteady fluid flows(e.g.,fluids interacting with moving structures,particles in turbulent flows,turbulent flame propagation),the memory effect is usually not considered and has not attracted much attention.The present study tries to highlight the importance of this memory effect based on a variety of examples.In this manner,the three key components characterizing the memory effect can be identified in a general manner.The central mechanism controlling the memory effect is then investigated by studying the flow over a shrinking particle.It is found that the Damköhler number comparing the timescales of the unsteady(trigger)event and of the feedback on the flow directly determines the intensity of the memory effect;a smaller Damköhler number results in a more intense effect.Finally,the flow induced by a flapping wing is considered to demonstrate that the memory effect could be also beneficial for practical applications,for instance for biomimetic locomotion.展开更多
Ammonia is emerging as a viable alternative to fossil fuels in combustion systems,aiding in the reduction of carbon emissions.However,its use faces challenges,including NOx emissions and low flame speed.Innovative app...Ammonia is emerging as a viable alternative to fossil fuels in combustion systems,aiding in the reduction of carbon emissions.However,its use faces challenges,including NOx emissions and low flame speed.Innovative approaches and technologies have significantly advanced the development and implementation of ammonia as a zero-carbon fuel.This review explores current advancements in using ammonia as a fuel substitute,highlighting the complexities that various systems need to overcome before reaching full commercial maturity in support of practical decarbon-ising global strategies.Different from other reviews,this article incorporates insights of various industrial partners currently working towards green ammonia technologies.The work further addresses fundamental complexities of ammonia combustion,crucial for its practical and industrial implementation in various types of equipment.展开更多
基金financial support by the DFG (project H2MAT3D,project number 523879740 within the DFG-SPP 2419 HyCAM)the Deutsche Forschungsgemeinschaft (DFG),Germany for its support within Project TH881/38-1 (DADOREN)。
文摘In this study,we perform a numerical investigation of a steady laminar stagnation flow flame stabilized at a wall with the consideration of heat transport,focusing on a lean hydrogen/air mixture with a fuel/air equivalence ratio 0.6.We discuss the NO emissions and their formation rates under various conditions,such as flow velocity and combustion pressure.It is found that the predominant reaction pathway for NO formation involves NNH radicals,though this changes near the wall surface.Beyond examining the wall's influence on flame structures,the present work focuses on the impact of combustion process on materials.Specifically,the accumulation of atomic hydrogen at the wall surface is explored,which is significant for the consequent modeling of potential hydrogen embrittlement.Additionally,the growth rate of oxide layers on the material surface increases significantly if the combustion pressure and consequently the combustion temperatures are enhanced.These investigations offer valuable insights into how combustion processes affect material,which is useful for designing engineering components under high-temperature environments.
基金support of the National Natural Science Foundation of China(No.52300183).
文摘Though being an important mechanism in systems involving unsteady fluid flows(e.g.,fluids interacting with moving structures,particles in turbulent flows,turbulent flame propagation),the memory effect is usually not considered and has not attracted much attention.The present study tries to highlight the importance of this memory effect based on a variety of examples.In this manner,the three key components characterizing the memory effect can be identified in a general manner.The central mechanism controlling the memory effect is then investigated by studying the flow over a shrinking particle.It is found that the Damköhler number comparing the timescales of the unsteady(trigger)event and of the feedback on the flow directly determines the intensity of the memory effect;a smaller Damköhler number results in a more intense effect.Finally,the flow induced by a flapping wing is considered to demonstrate that the memory effect could be also beneficial for practical applications,for instance for biomimetic locomotion.
基金supported by the Engineering and Physical Sciences Research Council(EPSRC)through the research projects:Storage of Ammonia For Energy(SAFE)-AGT Pilot(EP/T009314/1)Ocean-REFuel-Ocean Renewable Energy Fuels(EP/W005018/1).
文摘Ammonia is emerging as a viable alternative to fossil fuels in combustion systems,aiding in the reduction of carbon emissions.However,its use faces challenges,including NOx emissions and low flame speed.Innovative approaches and technologies have significantly advanced the development and implementation of ammonia as a zero-carbon fuel.This review explores current advancements in using ammonia as a fuel substitute,highlighting the complexities that various systems need to overcome before reaching full commercial maturity in support of practical decarbon-ising global strategies.Different from other reviews,this article incorporates insights of various industrial partners currently working towards green ammonia technologies.The work further addresses fundamental complexities of ammonia combustion,crucial for its practical and industrial implementation in various types of equipment.
