Hybrid engineering is gradually deemed as a powerful approach to solving the bottleneck problem of metal-organic framework (MOF) derived absorbers for practical application. Herein, a new type of semiconductor/carbon-...Hybrid engineering is gradually deemed as a powerful approach to solving the bottleneck problem of metal-organic framework (MOF) derived absorbers for practical application. Herein, a new type of semiconductor/carbon-based hybrid material was successfully prepared by phytic acid (PA) modification and carbonization of MOF/bacterial cellulose (BC) precursors, which remedied the drawbacks of structural instability, lethal byproducts and complicated steps reported previously. Specifically, the obtained Fe(PO3)2@C/phosphorus-doped carbon foam (Fe(PO3)2@C/PCF) had a 3D hybrid micro-nanostructure that integrated spatial microcurrent network, multi-level pores, heterogeneous interfaces and lattice defects, showing its unique advantages of low filler content (15 wt.%), moderate surface reflectivity, multi-band microwave absorption and radar stealth. The experimental analysis and CST simulation further revealed that PA dosage can precisely adjust the hybrid phase content, pore texture and electromagnetic parameters of the final product to achieve synergistic enhancement of multiple dielectric response, impedance matching and attenuation capacity. As a result, an effective bandwidth (EAB) of 6 GHz and a minimum reflection loss (RLmin) of -57.0 dB were obtained in the Ku- and C-bands, respectively. These encouraging results may advance the development of novel MOF-derived absorbents based on the hybridization principle.展开更多
In this study,a triple spark ignition scheme was first designed on a three-cylinder 1.5-L dedicated hybrid engine(DHE).On this basis,the effect of different ignition modes on engine combustion and emission characteris...In this study,a triple spark ignition scheme was first designed on a three-cylinder 1.5-L dedicated hybrid engine(DHE).On this basis,the effect of different ignition modes on engine combustion and emission characteristics was studied,especially under high dilution condition.The results tested at 2000 r/min and 0.8 MPa BMEP(brake mean effective pressure)show that with highly increased in-cylinder flow intensity,using only passive prechamber(PPC)has a lower lean limit than that with single central spark plug(CSP),thereby leading to slightly higher minimum fuel consumption and nitrogen oxides(NO_(x))emissions.Adding side spark plugs(SSP)based on PPC can result in improved capability of lean limit extension and engine performance than CSP.However,the improvement level is lower than that with triple spark plugs(TSP).As the excess air ratio λ increases,the advantage of PPC and PPC with SSP in improving the combustion phasing compared with CSP gradually weakens.Correspondingly,the increasing tendency of their ignition delay and combustion duration is more obvious.The added SSP based on PPC can effectively shorten the ignition delay of leaner mixture,but the combustion duration can be only slightly improved.As a result,under extremely lean condition,the advantage of PPC and PPC with SSP in terms of combustion characteristics over CSP becomes much smaller.In contrast,the TSP ignition can achieve much shorter ignition delay and combustion duration simultaneously under this condition.Due to the highest available dilution level,the TSP ignition achieves the lowest raw NO_(x)emissions.Moreover,it can also reduce the raw carbon monoxide(CO)and hydrocarbons(HC)emissions compared to CSP due to a more thorough combustion of the end gas mixture.Based on the excellent performance of TSP,the highest engine brake thermal efficiency(BTE)was further explored.The results show that with normal RON 92 fuel,the engine finally achieved 43.69% and 45.02% BTE under stochiometric mode with exhaust gas recirculation(EGR)and lean-burn mode respectively.When using RON 100 fuel,the highest BTE was further increased to 45.63%under lean-burn mode.展开更多
A new hybrid control scheme is presented with a robust multiple model fusion control（RMMFC） law for a UH-60 helicopter and an active disturbance rejection control（ADRC） controller for its engines.This scheme is a ...A new hybrid control scheme is presented with a robust multiple model fusion control（RMMFC） law for a UH-60 helicopter and an active disturbance rejection control（ADRC） controller for its engines.This scheme is a control design method with every subsystem designed separately but fully considering the couplings between them.With three subspaces with respect to forward flight velocity,a RMMFC is proposed to devise a four-loop reference signal tracing control for the helicopter,which escapes the closed-loop system from unstable state due to the extreme complexity of this integrated nonlinear system.The engines are controlled by the proposed ADRC decoupling controller,which fully takes advantage of a good compensation ability for unmodeled dynamics and extra disturbances,so as to compensate torque disturbance in power turbine speed loop.By simulating a forward acceleration flight task,the RMMFC for the helicopter is validated.It is apparent that the integrated helicopter and engine system（IHES） has much better dynamic performance under the new control scheme.Especially in the switching process,the large transient is significantly weakened,and smooth transition among candidate controllers is achieved.Over the entire simulation task,the droop of power turbine speed with the proposed ADRC controller is significantly slighter than with the conventional PID controller,and the response time of the former is much faster than the latter.By simulating a rapid climb and descent flight task,the results also show the feasibility for the application of the proposed multiple model fusion control.Although there is aggressive power demand in this maneuver,the droop of power turbine speed with an ADRC controller is smaller than using a PID controller.The control performance for helicopter and engine is enhanced by adopting this hybrid control scheme,and simulation results in other envelope state give proofs of robustness for this new scheme.展开更多
Emissions produced by the aviation industry are currently a severe environmental threat;therefore,aviation agencies and governments have set emission targets and formulated plans to restrict emissions within the next ...Emissions produced by the aviation industry are currently a severe environmental threat;therefore,aviation agencies and governments have set emission targets and formulated plans to restrict emissions within the next decade.Hybrid aircraft technology is being considered to meet these targets.The importance of these technologies lies in their advancements in terms of aircraft life cycles and environmental benignity.Owing to these advancements,hybrid electric systems with more than one power source have become promising for the aviation industry,considering that the growth of air traffic is projected to double in the next decade.Hybrid technologies have given future hybrid fans and motor-fan engines potential as alternative power generators.Herein,Turboelectric Distributed Propulsion(TeDP)is discussed in terms of power distribution and power sources.The fundamentals of turbofan and turboshaft engines are presented along with their electricitygeneration mechanism.TeDP is discussed from a design viewpoint,with a detailed discussion of different types of hybrid electric and turboelectric systems.Examples of proposed TeDP aircraft models and numerical modelling tools used to simulate the performance of TeDP models are reviewed.Finally,innovative turboelectric systems in which electric power savers and mechanical gear changers have been discarded for weight optimisation are presented along with other prospective models,engines,approaches,and architectures.The findings of this review indicate the knowledge gaps in the field of numerical modelling for NASA’s TeDP and its capability to increase the efficiency by up to 24%with a 50%reduction in emissions relative to those of conventional gas turbines.展开更多
The purpose of this paper is to present method of the numerical modeling of the hybrid rocket engine's work as a tool for designing engines of this type.The model is intended as an accurate and simple to use devel...The purpose of this paper is to present method of the numerical modeling of the hybrid rocket engine's work as a tool for designing engines of this type.The model is intended as an accurate and simple to use development tool for use in preliminary design stages of hybrid rocket engines,improving the effectiveness and quality of this process.General assumptions underlying the use of a model are presented,together with an analysis of past work in this field.Results of an extensive experimental campaign are presented and compared with the results of numerical modelling in order to calibrate the proposed model and evaluate its accuracy.Parameter variation and optimization were conducted,proving functionality of the methodology.Presented numerical calculations show that the adopted approach to reduce the analysis time and complexity was correct.This method of numerical calculation of hybrid engine working parameters combines aspects of accuracy and simplicity at the early design stage to avoid timeconsuming and costly changes in subsequent detailed stages of design.展开更多
To address the capacity degradation,voltage fading,structural instability and adverse interface reactions in cathode materi-als of lithium-ion batteries(LIBs),numerous modification strategies have been developed,mainl...To address the capacity degradation,voltage fading,structural instability and adverse interface reactions in cathode materi-als of lithium-ion batteries(LIBs),numerous modification strategies have been developed,mainly including coating and doping.In particular,the important strategy of doping(surface doping and bulk doping)has been considered an effective strategy to modulate the crystal lattice structure of cathode materials.However,special insights into the mechanisms and effectiveness of the doping strategy,especially comparisons between surface doping and bulk doping in cathode materials,are still lacking.In this review,recent significant progress in surface doping and bulk doping strategies is demonstrated in detail by focusing on their inherent differences as well as effects on the structural stability,lithium-ion(Li-ion)diffusion and electrochemical properties of cathode materials from the following mechanistic insights:preventing the exposure of reactive Ni on the surface,stabilizing the Li slabs,mitigating the migration of transition metal(TM)ions,alleviating unde-sired structural transformations and adverse interface issues,enlarging the Li interslab spacing,forming three-dimensional(3D)Li-ion diffusion channels,and providing more active sites for the charge-transfer process.Moreover,insights into the correlation between the mechanisms of hybrid surface engineering strategies(doping and coating)and their influences on the electrochemical performance of cathode materials are provided by emphasizing the stabilization of the Li slabs,the enhancement of the surface chemical stability,and the alleviation of TM ion migration.Furthermore,the existing challenges and future perspectives in this promising field are indicated.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2019YFE0122900)the National Natural Science Foundation of China(No.52373303)the Program of Shanghai Technology Research Leader(No.18XD1423800).
文摘Hybrid engineering is gradually deemed as a powerful approach to solving the bottleneck problem of metal-organic framework (MOF) derived absorbers for practical application. Herein, a new type of semiconductor/carbon-based hybrid material was successfully prepared by phytic acid (PA) modification and carbonization of MOF/bacterial cellulose (BC) precursors, which remedied the drawbacks of structural instability, lethal byproducts and complicated steps reported previously. Specifically, the obtained Fe(PO3)2@C/phosphorus-doped carbon foam (Fe(PO3)2@C/PCF) had a 3D hybrid micro-nanostructure that integrated spatial microcurrent network, multi-level pores, heterogeneous interfaces and lattice defects, showing its unique advantages of low filler content (15 wt.%), moderate surface reflectivity, multi-band microwave absorption and radar stealth. The experimental analysis and CST simulation further revealed that PA dosage can precisely adjust the hybrid phase content, pore texture and electromagnetic parameters of the final product to achieve synergistic enhancement of multiple dielectric response, impedance matching and attenuation capacity. As a result, an effective bandwidth (EAB) of 6 GHz and a minimum reflection loss (RLmin) of -57.0 dB were obtained in the Ku- and C-bands, respectively. These encouraging results may advance the development of novel MOF-derived absorbents based on the hybridization principle.
基金the financial support provided by Chongqing Technical Innovation and Application Development Project(cstc2020jscx-dxwtBX0024)China Internal Combustion Engine Society Youth Talent Promotion Program。
文摘In this study,a triple spark ignition scheme was first designed on a three-cylinder 1.5-L dedicated hybrid engine(DHE).On this basis,the effect of different ignition modes on engine combustion and emission characteristics was studied,especially under high dilution condition.The results tested at 2000 r/min and 0.8 MPa BMEP(brake mean effective pressure)show that with highly increased in-cylinder flow intensity,using only passive prechamber(PPC)has a lower lean limit than that with single central spark plug(CSP),thereby leading to slightly higher minimum fuel consumption and nitrogen oxides(NO_(x))emissions.Adding side spark plugs(SSP)based on PPC can result in improved capability of lean limit extension and engine performance than CSP.However,the improvement level is lower than that with triple spark plugs(TSP).As the excess air ratio λ increases,the advantage of PPC and PPC with SSP in improving the combustion phasing compared with CSP gradually weakens.Correspondingly,the increasing tendency of their ignition delay and combustion duration is more obvious.The added SSP based on PPC can effectively shorten the ignition delay of leaner mixture,but the combustion duration can be only slightly improved.As a result,under extremely lean condition,the advantage of PPC and PPC with SSP in terms of combustion characteristics over CSP becomes much smaller.In contrast,the TSP ignition can achieve much shorter ignition delay and combustion duration simultaneously under this condition.Due to the highest available dilution level,the TSP ignition achieves the lowest raw NO_(x)emissions.Moreover,it can also reduce the raw carbon monoxide(CO)and hydrocarbons(HC)emissions compared to CSP due to a more thorough combustion of the end gas mixture.Based on the excellent performance of TSP,the highest engine brake thermal efficiency(BTE)was further explored.The results show that with normal RON 92 fuel,the engine finally achieved 43.69% and 45.02% BTE under stochiometric mode with exhaust gas recirculation(EGR)and lean-burn mode respectively.When using RON 100 fuel,the highest BTE was further increased to 45.63%under lean-burn mode.
基金Funding of Jiangsu Innovation Program for Graduate Education (CXLX11_0213)Aeronautical Science Foundation of China (2010ZB52011)
文摘A new hybrid control scheme is presented with a robust multiple model fusion control（RMMFC） law for a UH-60 helicopter and an active disturbance rejection control（ADRC） controller for its engines.This scheme is a control design method with every subsystem designed separately but fully considering the couplings between them.With three subspaces with respect to forward flight velocity,a RMMFC is proposed to devise a four-loop reference signal tracing control for the helicopter,which escapes the closed-loop system from unstable state due to the extreme complexity of this integrated nonlinear system.The engines are controlled by the proposed ADRC decoupling controller,which fully takes advantage of a good compensation ability for unmodeled dynamics and extra disturbances,so as to compensate torque disturbance in power turbine speed loop.By simulating a forward acceleration flight task,the RMMFC for the helicopter is validated.It is apparent that the integrated helicopter and engine system（IHES） has much better dynamic performance under the new control scheme.Especially in the switching process,the large transient is significantly weakened,and smooth transition among candidate controllers is achieved.Over the entire simulation task,the droop of power turbine speed with the proposed ADRC controller is significantly slighter than with the conventional PID controller,and the response time of the former is much faster than the latter.By simulating a rapid climb and descent flight task,the results also show the feasibility for the application of the proposed multiple model fusion control.Although there is aggressive power demand in this maneuver,the droop of power turbine speed with an ADRC controller is smaller than using a PID controller.The control performance for helicopter and engine is enhanced by adopting this hybrid control scheme,and simulation results in other envelope state give proofs of robustness for this new scheme.
文摘Emissions produced by the aviation industry are currently a severe environmental threat;therefore,aviation agencies and governments have set emission targets and formulated plans to restrict emissions within the next decade.Hybrid aircraft technology is being considered to meet these targets.The importance of these technologies lies in their advancements in terms of aircraft life cycles and environmental benignity.Owing to these advancements,hybrid electric systems with more than one power source have become promising for the aviation industry,considering that the growth of air traffic is projected to double in the next decade.Hybrid technologies have given future hybrid fans and motor-fan engines potential as alternative power generators.Herein,Turboelectric Distributed Propulsion(TeDP)is discussed in terms of power distribution and power sources.The fundamentals of turbofan and turboshaft engines are presented along with their electricitygeneration mechanism.TeDP is discussed from a design viewpoint,with a detailed discussion of different types of hybrid electric and turboelectric systems.Examples of proposed TeDP aircraft models and numerical modelling tools used to simulate the performance of TeDP models are reviewed.Finally,innovative turboelectric systems in which electric power savers and mechanical gear changers have been discarded for weight optimisation are presented along with other prospective models,engines,approaches,and architectures.The findings of this review indicate the knowledge gaps in the field of numerical modelling for NASA’s TeDP and its capability to increase the efficiency by up to 24%with a 50%reduction in emissions relative to those of conventional gas turbines.
文摘The purpose of this paper is to present method of the numerical modeling of the hybrid rocket engine's work as a tool for designing engines of this type.The model is intended as an accurate and simple to use development tool for use in preliminary design stages of hybrid rocket engines,improving the effectiveness and quality of this process.General assumptions underlying the use of a model are presented,together with an analysis of past work in this field.Results of an extensive experimental campaign are presented and compared with the results of numerical modelling in order to calibrate the proposed model and evaluate its accuracy.Parameter variation and optimization were conducted,proving functionality of the methodology.Presented numerical calculations show that the adopted approach to reduce the analysis time and complexity was correct.This method of numerical calculation of hybrid engine working parameters combines aspects of accuracy and simplicity at the early design stage to avoid timeconsuming and costly changes in subsequent detailed stages of design.
基金the National Natural Science Foundation of China(52072298 and 51802261)the Local Special Service Program Funded by Education Department of Shaanxi Provincial Government(19JC031)+2 种基金the Natural Science Foundation of Shaanxi(2020JC-41,2021TD-15)the Xi’an Science and Technology Project of China(2019219714SYS012CG034)the Project 2019JLP-04 supported by the Joint Foundation of Shaanxi.
文摘To address the capacity degradation,voltage fading,structural instability and adverse interface reactions in cathode materi-als of lithium-ion batteries(LIBs),numerous modification strategies have been developed,mainly including coating and doping.In particular,the important strategy of doping(surface doping and bulk doping)has been considered an effective strategy to modulate the crystal lattice structure of cathode materials.However,special insights into the mechanisms and effectiveness of the doping strategy,especially comparisons between surface doping and bulk doping in cathode materials,are still lacking.In this review,recent significant progress in surface doping and bulk doping strategies is demonstrated in detail by focusing on their inherent differences as well as effects on the structural stability,lithium-ion(Li-ion)diffusion and electrochemical properties of cathode materials from the following mechanistic insights:preventing the exposure of reactive Ni on the surface,stabilizing the Li slabs,mitigating the migration of transition metal(TM)ions,alleviating unde-sired structural transformations and adverse interface issues,enlarging the Li interslab spacing,forming three-dimensional(3D)Li-ion diffusion channels,and providing more active sites for the charge-transfer process.Moreover,insights into the correlation between the mechanisms of hybrid surface engineering strategies(doping and coating)and their influences on the electrochemical performance of cathode materials are provided by emphasizing the stabilization of the Li slabs,the enhancement of the surface chemical stability,and the alleviation of TM ion migration.Furthermore,the existing challenges and future perspectives in this promising field are indicated.
