This article is aimed to experimentally validate the beneficial effects of boundary layer suction on improving the aerodynamic performance of a compressor cascade with a large camber angle. The flow field of the casca...This article is aimed to experimentally validate the beneficial effects of boundary layer suction on improving the aerodynamic performance of a compressor cascade with a large camber angle. The flow field of the cascade is measured and the ink-trace flow visualization is also presented. The experimental results show that the boundary layer suction reduces losses near the area of rnidspan in the cascade most effectively for all suction cases under test. Losses of the endwall could remarkably decrease only when the suction is at the position where the boundary layer has separated but still not departed far away from the blade surface. It is evidenced that the higher suction flow rate and the suction position closer to the trailing edge result in greater reduction in losses and the maximum reduction in the total pressure loss accounts to 16.5% for all cases. The suction position plays a greater role in affecting the total pressure loss than the suction flow rate does.展开更多
In the current study, the effects of a combined application between micro-vortex generator and boundary layer suction on the flow characteristics of a high-load compressor cascade are investigated. The micro-vortex ge...In the current study, the effects of a combined application between micro-vortex generator and boundary layer suction on the flow characteristics of a high-load compressor cascade are investigated. The micro-vortex generator with a special configuration and the longitudinal suction slot are adopted. The calculated results show that a reverse flow region, which is considered the main reason for occurring stall at 7.9° incidence, grows and collapses rapidly near the leading edge and leads to two critical points occurring on the end-wall with the increasing incidence in the baseline. As the micro-vortex generator is introduced in the baseline cascade, the corner separation is switched to a trailing edge separation by the thrust from the induced vortex. Meanwhile, the occurrence of failure is delayed due to the mixed low energy fluid and main flow. The synergistic effects between the micro-vortex generator and the boundary layer suction on the performance of the cascade are superior to the baseline at all the incidence conditions before the occurrence of failure, and the sudden deterioration of the cascade occurs at 10.3° incidence. The optimal results show that the farther upstream suction position, the lower total pressure loss of the cascade with vortex generator at the near stall condition. Moreover, the induced vortex with a leg can migrate the accumulated low energy fluid backward to delay the occurrence of stall.展开更多
It is well known that single-atom catalysts(SACs)have become a hot topic in the field of catalysis due to their advantages such as 100%metal atom utilization efficiency,high catalytic activity and selectivity compared...It is well known that single-atom catalysts(SACs)have become a hot topic in the field of catalysis due to their advantages such as 100%metal atom utilization efficiency,high catalytic activity and selectivity compared with conventional catalysts and nanocatalysts.However,the isolated metal atoms on SACs have thermodynamic instability and tend to agglomerate,which limit their catalytic performance.Therefore,it is of great significance to synthesize stable and high-loading single-atom catalysts(HLSACs).In this paper,we review the research progress of HLSACs from two aspects:design and application.Firstly,we comprehensively introduce the synthesis strategies of HLSACs,namely,top-down and bottom-up methods.Secondly,we overview the application status of HLSACs in three fields:electrocatalysis,thermal catalysis and photocatalysis.Finally,we summarize the development prospects and challenges of HLSACs.展开更多
Iron-based single-atom catalysts with nitrogen-doped carbon as support(Fe-SA/NPC)are considered effective alternatives to replace Pt-group metals for scalable application in fuel cells.However,synthesizing high-loadin...Iron-based single-atom catalysts with nitrogen-doped carbon as support(Fe-SA/NPC)are considered effective alternatives to replace Pt-group metals for scalable application in fuel cells.However,synthesizing high-loading Fe-SA catalysts by a simple procedure remains challenging.Herein,we report a high-loading(7.5 wt%)Fe-SA/NPC catalyst prepared by carbon-assisted pyrolysis of metal complexes.Both the nitrogen-doped porous carbon(NPC)support with high specific surface area and ο-phenylenediamine(o-PD)play key roles role in the preparation of high-loading Fe-SA/NPC catalysts.The results of X-ray photoelectron spectroscopy,high-angle annular dark-field scanning transmission electron microscopy,and X-ray absorption fine structure spectroscopy experiments show that the Fe atoms are anchored on the carbon carriers in a single-atom site configuration and coordinated with four of the doped nitrogen atoms of the carbon substrates(Fe-N_(4)).The activities of the Fe-SA/NPC catalysts in the oxygen reduction reaction increased with increasing iron loading.The optimized 250Fe-SA/NPC-800 catalyst exhibited an onset potential 0.97 V of and a half-wave potential of 0.85 V.Our study provides a simple approach for the large-scale synthesis of high-loading single-atom catalysts.展开更多
Sulfur utilization improvement and control of dissolved lithium polysulfide(LiPS;Li_(2)S x,2<x≤8)are cru-cial aspects of the development of lithium-sulfur(Li-S)batteries,especially in high-loading sulfur elec-trode...Sulfur utilization improvement and control of dissolved lithium polysulfide(LiPS;Li_(2)S x,2<x≤8)are cru-cial aspects of the development of lithium-sulfur(Li-S)batteries,especially in high-loading sulfur elec-trodes and low electrolyte/sulfur(E/S)ratios.The sluggish reaction in the low E/S ratio induces poor LiPS solubility and unstable Li_(2)S electrodeposition,resulting in limited sulfur utilization,especially under high-loading sulfur electrode.In this study,we report on salt concentration effects that improve sulfur utilization with a high-loading cathode(6 mgs ulfurcm^(-2)),a high sulfur content(80 wt%)and a low E/S ratio(5 m L gs ulfur^(-1)).On the basis of the rapid LiPS dissolving in a low concentration electrolyte,we estab-lished that the quantity of Li_(2)S electrodeposition from a high Li+diffusion coefficient,referring to the reduction of LiPS precipitation,was significantly enhanced by a faster kinetic.These results demonstrate the importance of kinetic factors for the rate capability and cycle life stability of Li-S battery electrolytes through high Li_(2)S deposition under high-loading sulfur electrode.展开更多
An effect of Mg introduction on efficiency of high-loaded nickel catalysts in dehydrogenation of decahydroquinoline(10HQ)was inves-tigated.10HQ dehydrogenation is key process for the liquid organic hydrogen carrier(LO...An effect of Mg introduction on efficiency of high-loaded nickel catalysts in dehydrogenation of decahydroquinoline(10HQ)was inves-tigated.10HQ dehydrogenation is key process for the liquid organic hydrogen carrier(LOHC)storage technology using the quinoline/10HQ pair as H_(2)-lean/H_(2)-rich substrates.An influence of synthesis technique of Ni/Mg/Al catalysts on their properties has been demonstrated.The catalysts were synthesized through coprecipitation of Ni,Mg,Al precursors to obtain layered double hydroxides(LDH)or via syn-thesis of(∼72 wt%)Ni-Al_(2)O_(3) system-also through coprecipitation,followed by modifying with a magnesium-containing precursor.For the catalysts of the first series,the inclusion of magnesium into LDH lattice led to a significant increase in catalytic activity in hydrogen extraction(10HQ dehydrogenation reaction).Despite the decrease in the content of catalytically active nickel,a significant increase in the yield of the dehydrogenation product was observed.This regularity is presumably associated with appearance of basic sites,that accelerates the dehydrogenation reaction.In the case of the second series,activity of pre-reduced(600°C,H_(2))catalysts in dehydrogenation of 10HQ also significantly depends on a MgO content and is maximal at Mg:Ni weight ratio 0.056.Using an in-depth study of structure of the original and reduced catalyst samples(Ni-Al_(2)O_(3) and Ni-MgNiOx-Al_(2)O_(3)),it was shown that this regularity is associated with the increased resistance of catalytically active Ni particles to agglomeration during the reductive activation.Also,using the Ni-MgNiOx-Al_(2)O_(3)catalyst for hydrogen storage process(hydrogenation reaction),the possibility of deep quinoline hydrogenation(up to 10HQ)in a flow-type reactor was demonstrated for the first time.展开更多
As the persistent concerns regarding sluggish reaction kinetics and insufficient conductivities of sulfur cathodes in all-solid-state Li-S batteries(ASSLSBs),numerous carbon additives and solid-state electrolytes(SSEs...As the persistent concerns regarding sluggish reaction kinetics and insufficient conductivities of sulfur cathodes in all-solid-state Li-S batteries(ASSLSBs),numerous carbon additives and solid-state electrolytes(SSEs)have been incorporated into the cathode to facilitate ion/electron pathways around sulfur.However,this has resulted in a reduced capacity and decomposition of SSEs.Therefore,it is worth exploring neotype sulfur hosts with electronic/ionic conductivity in the cathode.Herein,we present a hybrid cathode composed of few-layered S/MoS_(2)/C nanosheets(<5 layers)that exhibits high-loading and long-life performance without the need of additional carbon additives in advanced ASSLSBs.The multifunctional MoS_(2)/C host exposes the abundant surface for intimate contacting sites,in situ-formed LixMoS_(2)during discharging as mixed ion/electron conductive network improves the S/Li2S conversion,and contributes extra capacity for the part of active materials.With a high active material content(S+MoS_(2)/C)of 60 wt%in the S/MoS_(2)/C/Li_(6)PS_(5)Cl cathode composite(the carbon content is only~3.97 wt%),the S/MoS_(2)/C electrode delivers excellent electrochemical performance,with a high reversible discharge capacity of 980.3 mAh g^(-1)(588.2 mAh g^(-1)based on the whole cathode weight)after 100 cycles at 100 mA g^(-1).The stable cycling performance is observed over 3500 cycles with a Coulombic efficiency of 98.5%at 600 mA g^(-1),while a high areal capacity of 10.4 mAh cm^(-2)is achieved with active material loading of 12.8 mg cm^(-2).展开更多
This paper examines how variations in the radial distribution of tip winglets affect high-load compressor stage performance.The study modifies the radial distribution by altering tip winglets’circumferential widest p...This paper examines how variations in the radial distribution of tip winglets affect high-load compressor stage performance.The study modifies the radial distribution by altering tip winglets’circumferential widest position and radial height,analyzing twelve distinct configurations.These modifications influence the effective flow area within the compressor stage,subsequently changing the shock wave structure on the blade surfaces.The effectiveness of the tip winglet structures in managing the flow field is linked to their ability to achieve aerodynamic balance with complex flow structures,such as leakage flow and shock waves.Furthermore,as the tip winglets extend towards the rotor root,they redistribute fluid,thereby preventing the concentration of low-energy fluid in the radial region.This adjustment significantly improves the internal flow structure of the compressor and enhances flow stability.The findings reveal that the expansion effect of the tip winglets increases simultaneously with their circumferential widest position moving towards the leading edge and their radial initial position extending towards the rotor root.Therefore,there is a maximum stability margin increase of 44.57%.For this study,the optimal circumferential widest position of the tip winglet is located at 25%chord length,with the radial initial position at 80%span.展开更多
Controllable speed casing (CSC) represents an innovative development in casing treatment technology,wherein the traditional stationary casing is reconfigured into two components:a rotatable ring and a stationary ring....Controllable speed casing (CSC) represents an innovative development in casing treatment technology,wherein the traditional stationary casing is reconfigured into two components:a rotatable ring and a stationary ring.Initial position (IP) of the rotatable ring is a cntical parameter affecting the operational effectiveness of CSC.This study investigates the influence of varying IP of the rotatable ring on the aerodynamic performance and flow stability of a high-load compressor stage,with terminal position (TP) fixed at the rotor tip trailing edge.The results reveal that positioning the rotatable ring near the rotor tip trailing edge leads to moderate improvements in stability by controlling the secondary flow at the trailing edge.However,when IP coincides with the region where the tip leakage vortex and induced vortex breakdown,CSC disrupts the upstream flow,increasing the blockage of low-energy fluid,thereby precipitating an early stall in the compressor.Conversely,positioning IP at the rotor leading edge enables CSC to effectively manage tip leakage flow,facilitating the deflection of the tip leakage vortex away from the adjacent blade pressure surface.This adjustment mitigates the blocking effect within the blade tip passage,thereby significantly enhancing the compressor's flow stability.Under these optimal conditions,CSC achieves a substantial 45.11%improvement in stable operating margin of the compressor.展开更多
The synthesis of Pt intermetallic compounds(IMCs)typically necessitates high-temperature annealing to overcome the atom-diffusion kinetic barrier,which inevitably results in considerable nanoparticle sintering,especia...The synthesis of Pt intermetallic compounds(IMCs)typically necessitates high-temperature annealing to overcome the atom-diffusion kinetic barrier,which inevitably results in considerable nanoparticle sintering,especially for the high-loaded catalyst,thus leading to diminished performance in proton exchange membrane fuel cells.We propose a concentration-gradient-driven atom diffusion strategy to synthesize Pt intermetallic compounds(IMCs),overcoming the atom-diffusion kinetic barrier under relatively low temperature.This method efficiently transforms high-loaded Pt seeds/C into sub-5 nm L10-PtCo-IMC/C(44.3 wt%)catalyst.Advanced characterizations and molecular dynamic simulations reveal that locally concentrated Co precursors accelerate atom diffusion and enhance nanoparticle anti-sintering ability.Temperature-dependent analyses further elucidate the structural transformation mechanism by tracking crystal structure and nanoparticle size evolution.Membrane electrode assembly(MEA)integrated with the optimized PtCo-IMC/C at a low Pt usage(0.1 mg cm^(-2))delivers a maximum power density of approximately 1.15 W cm^(-2)and excellent stability(a 26-mV loss at 0.8 A cm^(-2))after 30000 cycles of accelerated stress testing under H_(2)-air conditions.This scalable synthesis pathway(20 g per batch)holds great promise for advancing high-loaded fuel cell electrocatalysts.展开更多
Titanium dioxides have been extensively investigated as promising anodes for Lithium ion batteries(LIBs)because of the high–rate capacity and cyclability,as well as the improved safety over graphite anode(1,2)However...Titanium dioxides have been extensively investigated as promising anodes for Lithium ion batteries(LIBs)because of the high–rate capacity and cyclability,as well as the improved safety over graphite anode(1,2)However,as a typical insertion–type anode,anatase TiO2 exhibits low conductivity(10–12S cm-1 for electron conductivity[3]and 10–17–10–10 cm2 s1 for Li+ion diffusion coefficient[4])and poor specific capacity(only accommodate<0.5 Li per bulk TiO2 unit[5]),severely limiting its practical applications.展开更多
基金National Basic Research Program of China (2007CB210100)National Natural Science Foundation of China (50876023)Chinese Specialized Research Fund for the Doctoral Program of Higher Education (20060213007)
文摘This article is aimed to experimentally validate the beneficial effects of boundary layer suction on improving the aerodynamic performance of a compressor cascade with a large camber angle. The flow field of the cascade is measured and the ink-trace flow visualization is also presented. The experimental results show that the boundary layer suction reduces losses near the area of rnidspan in the cascade most effectively for all suction cases under test. Losses of the endwall could remarkably decrease only when the suction is at the position where the boundary layer has separated but still not departed far away from the blade surface. It is evidenced that the higher suction flow rate and the suction position closer to the trailing edge result in greater reduction in losses and the maximum reduction in the total pressure loss accounts to 16.5% for all cases. The suction position plays a greater role in affecting the total pressure loss than the suction flow rate does.
基金co-supported by the National Natural Science Foundation of China(Grants Nos.51576162 and 51536006)
文摘In the current study, the effects of a combined application between micro-vortex generator and boundary layer suction on the flow characteristics of a high-load compressor cascade are investigated. The micro-vortex generator with a special configuration and the longitudinal suction slot are adopted. The calculated results show that a reverse flow region, which is considered the main reason for occurring stall at 7.9° incidence, grows and collapses rapidly near the leading edge and leads to two critical points occurring on the end-wall with the increasing incidence in the baseline. As the micro-vortex generator is introduced in the baseline cascade, the corner separation is switched to a trailing edge separation by the thrust from the induced vortex. Meanwhile, the occurrence of failure is delayed due to the mixed low energy fluid and main flow. The synergistic effects between the micro-vortex generator and the boundary layer suction on the performance of the cascade are superior to the baseline at all the incidence conditions before the occurrence of failure, and the sudden deterioration of the cascade occurs at 10.3° incidence. The optimal results show that the farther upstream suction position, the lower total pressure loss of the cascade with vortex generator at the near stall condition. Moreover, the induced vortex with a leg can migrate the accumulated low energy fluid backward to delay the occurrence of stall.
基金financially supported by Beijing Natural Science Foundation(No.2212018)Beijing Institute of Technology Research Fund Program for Young Scholars(No.2022CX01011)+3 种基金Ningbo 3315 Innovative Teams Program(No.2019A-14-C)the National Natural Science Foundation of China(No.12374390)the Member of Youth Innovation Promotion Association Foundation of CAS,China(No.2023310)the Key Scientific and Technological Special Project of Ningbo City No.(2023Z209)。
文摘It is well known that single-atom catalysts(SACs)have become a hot topic in the field of catalysis due to their advantages such as 100%metal atom utilization efficiency,high catalytic activity and selectivity compared with conventional catalysts and nanocatalysts.However,the isolated metal atoms on SACs have thermodynamic instability and tend to agglomerate,which limit their catalytic performance.Therefore,it is of great significance to synthesize stable and high-loading single-atom catalysts(HLSACs).In this paper,we review the research progress of HLSACs from two aspects:design and application.Firstly,we comprehensively introduce the synthesis strategies of HLSACs,namely,top-down and bottom-up methods.Secondly,we overview the application status of HLSACs in three fields:electrocatalysis,thermal catalysis and photocatalysis.Finally,we summarize the development prospects and challenges of HLSACs.
文摘Iron-based single-atom catalysts with nitrogen-doped carbon as support(Fe-SA/NPC)are considered effective alternatives to replace Pt-group metals for scalable application in fuel cells.However,synthesizing high-loading Fe-SA catalysts by a simple procedure remains challenging.Herein,we report a high-loading(7.5 wt%)Fe-SA/NPC catalyst prepared by carbon-assisted pyrolysis of metal complexes.Both the nitrogen-doped porous carbon(NPC)support with high specific surface area and ο-phenylenediamine(o-PD)play key roles role in the preparation of high-loading Fe-SA/NPC catalysts.The results of X-ray photoelectron spectroscopy,high-angle annular dark-field scanning transmission electron microscopy,and X-ray absorption fine structure spectroscopy experiments show that the Fe atoms are anchored on the carbon carriers in a single-atom site configuration and coordinated with four of the doped nitrogen atoms of the carbon substrates(Fe-N_(4)).The activities of the Fe-SA/NPC catalysts in the oxygen reduction reaction increased with increasing iron loading.The optimized 250Fe-SA/NPC-800 catalyst exhibited an onset potential 0.97 V of and a half-wave potential of 0.85 V.Our study provides a simple approach for the large-scale synthesis of high-loading single-atom catalysts.
基金supported by a grant from the Korea Evaluation Institute of Industrial Technology(KEIT)funded by the Ministry of Trade,Industry and Energy(MOTIE)(No.20012341)。
文摘Sulfur utilization improvement and control of dissolved lithium polysulfide(LiPS;Li_(2)S x,2<x≤8)are cru-cial aspects of the development of lithium-sulfur(Li-S)batteries,especially in high-loading sulfur elec-trodes and low electrolyte/sulfur(E/S)ratios.The sluggish reaction in the low E/S ratio induces poor LiPS solubility and unstable Li_(2)S electrodeposition,resulting in limited sulfur utilization,especially under high-loading sulfur electrode.In this study,we report on salt concentration effects that improve sulfur utilization with a high-loading cathode(6 mgs ulfurcm^(-2)),a high sulfur content(80 wt%)and a low E/S ratio(5 m L gs ulfur^(-1)).On the basis of the rapid LiPS dissolving in a low concentration electrolyte,we estab-lished that the quantity of Li_(2)S electrodeposition from a high Li+diffusion coefficient,referring to the reduction of LiPS precipitation,was significantly enhanced by a faster kinetic.These results demonstrate the importance of kinetic factors for the rate capability and cycle life stability of Li-S battery electrolytes through high Li_(2)S deposition under high-loading sulfur electrode.
基金supported by the Ministry of Science and Higher Education of the Russian Federation within governmental order for Boreskov Institute of Catalysis SB RAS (projects FWUR-2024–0038, FWUR-2024–0032 and FWUR2024–0039)
文摘An effect of Mg introduction on efficiency of high-loaded nickel catalysts in dehydrogenation of decahydroquinoline(10HQ)was inves-tigated.10HQ dehydrogenation is key process for the liquid organic hydrogen carrier(LOHC)storage technology using the quinoline/10HQ pair as H_(2)-lean/H_(2)-rich substrates.An influence of synthesis technique of Ni/Mg/Al catalysts on their properties has been demonstrated.The catalysts were synthesized through coprecipitation of Ni,Mg,Al precursors to obtain layered double hydroxides(LDH)or via syn-thesis of(∼72 wt%)Ni-Al_(2)O_(3) system-also through coprecipitation,followed by modifying with a magnesium-containing precursor.For the catalysts of the first series,the inclusion of magnesium into LDH lattice led to a significant increase in catalytic activity in hydrogen extraction(10HQ dehydrogenation reaction).Despite the decrease in the content of catalytically active nickel,a significant increase in the yield of the dehydrogenation product was observed.This regularity is presumably associated with appearance of basic sites,that accelerates the dehydrogenation reaction.In the case of the second series,activity of pre-reduced(600°C,H_(2))catalysts in dehydrogenation of 10HQ also significantly depends on a MgO content and is maximal at Mg:Ni weight ratio 0.056.Using an in-depth study of structure of the original and reduced catalyst samples(Ni-Al_(2)O_(3) and Ni-MgNiOx-Al_(2)O_(3)),it was shown that this regularity is associated with the increased resistance of catalytically active Ni particles to agglomeration during the reductive activation.Also,using the Ni-MgNiOx-Al_(2)O_(3)catalyst for hydrogen storage process(hydrogenation reaction),the possibility of deep quinoline hydrogenation(up to 10HQ)in a flow-type reactor was demonstrated for the first time.
基金the financial support from the National Natural Science Foundation of China(T2241003)the National Key Research and Development Program of China(2022YFB4003500)the Key R&D project of Hubei Province,China(2021AAA006)
文摘As the persistent concerns regarding sluggish reaction kinetics and insufficient conductivities of sulfur cathodes in all-solid-state Li-S batteries(ASSLSBs),numerous carbon additives and solid-state electrolytes(SSEs)have been incorporated into the cathode to facilitate ion/electron pathways around sulfur.However,this has resulted in a reduced capacity and decomposition of SSEs.Therefore,it is worth exploring neotype sulfur hosts with electronic/ionic conductivity in the cathode.Herein,we present a hybrid cathode composed of few-layered S/MoS_(2)/C nanosheets(<5 layers)that exhibits high-loading and long-life performance without the need of additional carbon additives in advanced ASSLSBs.The multifunctional MoS_(2)/C host exposes the abundant surface for intimate contacting sites,in situ-formed LixMoS_(2)during discharging as mixed ion/electron conductive network improves the S/Li2S conversion,and contributes extra capacity for the part of active materials.With a high active material content(S+MoS_(2)/C)of 60 wt%in the S/MoS_(2)/C/Li_(6)PS_(5)Cl cathode composite(the carbon content is only~3.97 wt%),the S/MoS_(2)/C electrode delivers excellent electrochemical performance,with a high reversible discharge capacity of 980.3 mAh g^(-1)(588.2 mAh g^(-1)based on the whole cathode weight)after 100 cycles at 100 mA g^(-1).The stable cycling performance is observed over 3500 cycles with a Coulombic efficiency of 98.5%at 600 mA g^(-1),while a high areal capacity of 10.4 mAh cm^(-2)is achieved with active material loading of 12.8 mg cm^(-2).
基金the Key Project of the National Nature Science Foundation of China(NSFC,Grant No.52236005)the Key Project of the Center for Basic Science of Aeroengine and Gas Turbine(Grant No.P2022-B-II-007-001).
文摘This paper examines how variations in the radial distribution of tip winglets affect high-load compressor stage performance.The study modifies the radial distribution by altering tip winglets’circumferential widest position and radial height,analyzing twelve distinct configurations.These modifications influence the effective flow area within the compressor stage,subsequently changing the shock wave structure on the blade surfaces.The effectiveness of the tip winglet structures in managing the flow field is linked to their ability to achieve aerodynamic balance with complex flow structures,such as leakage flow and shock waves.Furthermore,as the tip winglets extend towards the rotor root,they redistribute fluid,thereby preventing the concentration of low-energy fluid in the radial region.This adjustment significantly improves the internal flow structure of the compressor and enhances flow stability.The findings reveal that the expansion effect of the tip winglets increases simultaneously with their circumferential widest position moving towards the leading edge and their radial initial position extending towards the rotor root.Therefore,there is a maximum stability margin increase of 44.57%.For this study,the optimal circumferential widest position of the tip winglet is located at 25%chord length,with the radial initial position at 80%span.
基金the Key Project of the National Nature Science Foundation of China (Grant No.52236005)the Key Project of the Center for Basic Science of Aeroengine and Gas Turbine (Grant No.P2022-B-Ⅱ-007-001) for funding this work。
文摘Controllable speed casing (CSC) represents an innovative development in casing treatment technology,wherein the traditional stationary casing is reconfigured into two components:a rotatable ring and a stationary ring.Initial position (IP) of the rotatable ring is a cntical parameter affecting the operational effectiveness of CSC.This study investigates the influence of varying IP of the rotatable ring on the aerodynamic performance and flow stability of a high-load compressor stage,with terminal position (TP) fixed at the rotor tip trailing edge.The results reveal that positioning the rotatable ring near the rotor tip trailing edge leads to moderate improvements in stability by controlling the secondary flow at the trailing edge.However,when IP coincides with the region where the tip leakage vortex and induced vortex breakdown,CSC disrupts the upstream flow,increasing the blockage of low-energy fluid,thereby precipitating an early stall in the compressor.Conversely,positioning IP at the rotor leading edge enables CSC to effectively manage tip leakage flow,facilitating the deflection of the tip leakage vortex away from the adjacent blade pressure surface.This adjustment mitigates the blocking effect within the blade tip passage,thereby significantly enhancing the compressor's flow stability.Under these optimal conditions,CSC achieves a substantial 45.11%improvement in stable operating margin of the compressor.
基金supported by the National Natural Science Foundation of China(22472193)Shanghai Rising-Star Program(24QA2710500,Shanghai Scientific and Technological Committee)+2 种基金Shanghai Science and Technology Innovation Action Plan(23ZR1471000,22511102500)Key Research and Development Project of Guangdong Province(2023B0909060003)the BL14W1 beamline at Shanghai Synchrotron Radiation Facility(SSRF).
文摘The synthesis of Pt intermetallic compounds(IMCs)typically necessitates high-temperature annealing to overcome the atom-diffusion kinetic barrier,which inevitably results in considerable nanoparticle sintering,especially for the high-loaded catalyst,thus leading to diminished performance in proton exchange membrane fuel cells.We propose a concentration-gradient-driven atom diffusion strategy to synthesize Pt intermetallic compounds(IMCs),overcoming the atom-diffusion kinetic barrier under relatively low temperature.This method efficiently transforms high-loaded Pt seeds/C into sub-5 nm L10-PtCo-IMC/C(44.3 wt%)catalyst.Advanced characterizations and molecular dynamic simulations reveal that locally concentrated Co precursors accelerate atom diffusion and enhance nanoparticle anti-sintering ability.Temperature-dependent analyses further elucidate the structural transformation mechanism by tracking crystal structure and nanoparticle size evolution.Membrane electrode assembly(MEA)integrated with the optimized PtCo-IMC/C at a low Pt usage(0.1 mg cm^(-2))delivers a maximum power density of approximately 1.15 W cm^(-2)and excellent stability(a 26-mV loss at 0.8 A cm^(-2))after 30000 cycles of accelerated stress testing under H_(2)-air conditions.This scalable synthesis pathway(20 g per batch)holds great promise for advancing high-loaded fuel cell electrocatalysts.
基金supported by the National Natural Science Foundation of China (51772163)the State Key Laboratory of New Ceramic and Fine Processing Tsinghua University (KF201801)
文摘Titanium dioxides have been extensively investigated as promising anodes for Lithium ion batteries(LIBs)because of the high–rate capacity and cyclability,as well as the improved safety over graphite anode(1,2)However,as a typical insertion–type anode,anatase TiO2 exhibits low conductivity(10–12S cm-1 for electron conductivity[3]and 10–17–10–10 cm2 s1 for Li+ion diffusion coefficient[4])and poor specific capacity(only accommodate<0.5 Li per bulk TiO2 unit[5]),severely limiting its practical applications.
