The active cooling technology that can reduce the combustor temperature is commonly used to protect the scramjet.In order to further improve the performance of active cooling,the structural weight reduction,cooling ef...The active cooling technology that can reduce the combustor temperature is commonly used to protect the scramjet.In order to further improve the performance of active cooling,the structural weight reduction,cooling efficiency and stress level of the cooling channel must be considered simultaneously.In this paper,new types of lattice channels for active cooling were designed and compared with the conventional cooling channel in terms of weight reduction,thermal and structural performance.The results showed that,at the same channel height,the cooling channel with staggered lattice arrays has the optimal comprehensive performance:the weight reduction effect reaches 39.93%;the wall temperature drops significantly,and the maximum Nu number is 2.155times of the conventional channel.The flow field analysis showed that horseshoe vortices formed by the impact effect and hairpin vortices near the trailing edge are the main factors of heat transfer enhancement.The disturbed boundary layer and the excited turbulent kinetic energy also contribute much to enhance the heat transfer.In addition,due to the HTE-induced increment of metal tensile strength,the system reliability of lattice channel is better than the conventional one.展开更多
Actively cooled thermal protection system has great influence on the engine of a hypersonic vehicle, and it is significant to obtain the thermal and stress distribution in the system. So an analytic estimation and num...Actively cooled thermal protection system has great influence on the engine of a hypersonic vehicle, and it is significant to obtain the thermal and stress distribution in the system. So an analytic estimation and numerical modeling are performed in this paper to investigate the behavior of an actively cooled thermal protection system. The analytic estimation is based on the electric analogy method and finite element analysis（FEA） is applied to the numerical simulation. Temperature and stress distributions are obtained for the actively cooled channel walls with three kinds of nickel alloys with or with no thermal barrier coating（TBC）. The temperature of the channel wall with coating has no obvious difference from the one with no coating, but the stress with coating on the channel wall is much smaller than that with no coating. Inconel X-750 has the best characteristics among the three Ni-based materials due to its higher thermal conductivity, lower elasticity module and greater allowable stress. Analytic estimation and numerical modeling results are compared with each other and a reasonable agreement is obtained.展开更多
Transpiration cooling thermal protection systems(TPS)are investigated for potential applications in hypersonic and re-entry vehicles,which are subjected to the severe aerodynamic heating environment.In this paper a tr...Transpiration cooling thermal protection systems(TPS)are investigated for potential applications in hypersonic and re-entry vehicles,which are subjected to the severe aerodynamic heating environment.In this paper a transpiration cooling thermal protection system was designed and manufactured,and an experiment platform with radiant heating at the bottom as heat source was developed.The cooling capacity of the transpiration cooling TPS was experimentally investigated.By combining transpiration cooling method with traditional TPS,the heat load capability of the TPS can be improved.The structure temperature with active cooling applied was much lower than that without active cooling applied under the same heat load as well as the heat load increased with active cooling than the one without active cooling for the same structure temperature.The experimental results showed that at 5800 s,the temperature of inner structure was 100°C with active cooling applied compared to 500°C without active cooling applied,then the temperature increased and reached to 360°C at 8300 s.Heat load of this transpiration cooling TPS can be increased by over 70%as compared to the passion one and the cooling capability of the transpiration TPS was about 1700 kJ/kg.The results can provide fundamental data for developing the transpiration cooling TPS.展开更多
With the increasing global energy consumption and cooling demands,traditional active cooling technologies face inefficiency and environmental challenges.Recently published in Science,a team led by Prof.Hai-bo Zhao has...With the increasing global energy consumption and cooling demands,traditional active cooling technologies face inefficiency and environmental challenges.Recently published in Science,a team led by Prof.Hai-bo Zhao has proposed and developed a biomass-based photoluminescent aerogel made from DNA and gelatin to address these challenges.This material achieves a solar-weighted reflectance of over 100%(0.4-0.8μm)and provides a cooling effect of 16.0℃under sunlight.This sustainable material is repairable,recyclable,and biodegradable,offering significant potential for energy-efficient buildings and wearable cooling devices.展开更多
Active cooling of aircraft skin has garnered significant attention from researchers in recent years due to the increasing flight speeds.The determination of the maximum temperature plays a crucial role in the design o...Active cooling of aircraft skin has garnered significant attention from researchers in recent years due to the increasing flight speeds.The determination of the maximum temperature plays a crucial role in the design of active cooling systems as it dictates the selection of suitable materials for aircraft skin.This research presents two analytical models for predicting surface temperatures in aircraft skin with active cooling channels:one for densely arranged channels and another for sparsely arranged channels.The application criteria of these two models are obtained.The analytical models offer several advantages,including handling non-uniform heat fluxes and providing direct predictions of maximum temperature and its location.Numerical simulations validate these models,demonstrating their accurate estimation capabilities across various solid materials,Reynolds numbers,and thermal conductivities.This investigation lays the foundation for rapid and cost-effective design of optimal cooling channels based on solid thermal conductivity,cooling flow rate,channel spacing,and temperature limits under non-uniform heat flows.Furthermore,an examination of channel aspect ratios reveals that larger ratios result in lower heated surface temperatures.Overall,these analytical temperature prediction models serve as efficient tools for selecting appropriate design parameters for active cooling channels.展开更多
Located in the eastern margin of the Tibetan Plateau,the Gonghe-Yushu high-grade highway was the first of its kind in plateau permafrost regions.Most of the road sections along the high-grade highway are unstable or e...Located in the eastern margin of the Tibetan Plateau,the Gonghe-Yushu high-grade highway was the first of its kind in plateau permafrost regions.Most of the road sections along the high-grade highway are unstable or extremely unstable warm permafrost with an average annual ground temperature above−1℃,which is vulnerable to global warming and human engineering activities.This paper describes permafrost characteristics,roadbed design,and operation of the Gonghe-Yushu high-grade highway in detail.It is found that thaw settlement of warm and ice-rich permafrost is the main cause of subgrade subsidence in permafrost sections of this highway due to insufficient permafrost survey and drainage design.It is recommended that the interception and drainage system's design be optimized,and the permafrost upper limit and the variation of ground temperature be further investigated to provide essential data for the treatment of highway distress.It should be emphasized that protecting permafrost soil environment and optimized engineering design are crucial to successful high-grade highway engineering in permafrost regions.展开更多
Active regenerative cooling with supercritical hydrocarbon fuel is considered as the most promising thermal protection method.The existence of buoyancy force would lead to strongly anisotropic flow and thermal transpo...Active regenerative cooling with supercritical hydrocarbon fuel is considered as the most promising thermal protection method.The existence of buoyancy force would lead to strongly anisotropic flow and thermal transport characteristics.It is closely related to the cooling performance of the engine.To elucidate the mechanisms of turbulent transport,the large eddy simulation(LES) was performed to assess turbulence statistics within different turbulence scales.The results indicated that the buoyancy and inertial force together dominated the change of turbulent structure.Moreover,the spatial thermal buoyancy effect significantly suppressed the vertical velocity fluctuation.This is due to the laminar motion caused by the buoyancy force,thereby weakening the thermal transport.For the statistics of velocity fluctuation,it was found that the buoyancy force and inertial force greatly weaken the vertical and streamwise velocity fluctuation,respectively.For the statistics of thermal transport,the results pointed out that the near-wall heat transport characteristics need to be paid more attention.The thickness of the temperature mixing boundary layer led to the attenuation of vertical heat flux,which inhibited vertical temperature diffusion and predisposed to extreme conditions of heat transfer deterioration.The results can enhance the academic understanding of the heat transfer mechanism of supercritical fluids,and give guidance for further applications of thermal protection.展开更多
The oblique detonation chamber has an extreme high and uneven thermal load due to the fast exothermic combustion process induced by oblique shock wave.The active cooling technology of over-pressure water is an effecti...The oblique detonation chamber has an extreme high and uneven thermal load due to the fast exothermic combustion process induced by oblique shock wave.The active cooling technology of over-pressure water is an effective thermal protection method with the development of additive manufacturing technology.The realizable κ-ε model coupling with Volume Fraction(VOF) model is applied to solve the boiling flow of cooling water in the mini-channels.The phase transition and heat transfer characteristics are systematically investigated under different pressures.The phase transition process is first observed in the position of oblique detonation wave,and the bubbly flow,the slug flow,the annular flow and the churn flow are captured in the characteristic cooling channel when boiling flow reaching steady stage.In the rear section of the channel,the uneven heat flux distribution of combustion chamber brings to the churn flow,which enhances the heat transfer compared to the annular flow.Compared to the atmospheric water,the appearances of churn flow and annular flow are significantly decreased with the increasing pressure,and they would disappear when the pressure is exceeding 0.5 MPa.The bubbly flow and slug flow play a dominant role when the pressure is higher than 1 MPa,showing that the over-pressure water can significantly enhance the cooling efficiency of the oblique detonation chamber.With the rise of water pressure,the time point of the appearance of phase transition is obviously lagged because of the increasing latent heat of vaporization,and the cooling efficiency is significantly increased due to the simpler phase transition in higher pressure,which means the over-pressure water could withstand longer heat load of oblique detonation engine.展开更多
Objective: To study the curative effect of Chinese medicines in treating severe cholestatic hepatitis (SCH).Methods: Three hundred and fifty patients of SCH with total bilirubin level 171 μmol/L were treated with Chi...Objective: To study the curative effect of Chinese medicines in treating severe cholestatic hepatitis (SCH).Methods: Three hundred and fifty patients of SCH with total bilirubin level 171 μmol/L were treated with Chinese medicines. Those with Blood Stasis Syndrome were treated with the recipe mainly consisting of Radix Paeoniae Rubra, and those accompanied by blood Heat, fluid retention in the epigastric region, dampness disseminated in Sanjiao ( ) or Yang deficiency of both Spleen and Kidney were treated with recipe modified according to the symptoms and signs.Results: The treatment was markedly effective in 288 cases and effective in 26 cases, the total effective rate being 89.7%.Conclusion: It is difficult to treat severe cholestatic hepatitis, es pecially the chronic cholestatic good effect of Chinese herbal medicine in eliminating jaundice.展开更多
基金supported by the National Natural Science Foundation of China(51876132)the Science and Technology on Scramjet Laboratory(6142703190101)。
文摘The active cooling technology that can reduce the combustor temperature is commonly used to protect the scramjet.In order to further improve the performance of active cooling,the structural weight reduction,cooling efficiency and stress level of the cooling channel must be considered simultaneously.In this paper,new types of lattice channels for active cooling were designed and compared with the conventional cooling channel in terms of weight reduction,thermal and structural performance.The results showed that,at the same channel height,the cooling channel with staggered lattice arrays has the optimal comprehensive performance:the weight reduction effect reaches 39.93%;the wall temperature drops significantly,and the maximum Nu number is 2.155times of the conventional channel.The flow field analysis showed that horseshoe vortices formed by the impact effect and hairpin vortices near the trailing edge are the main factors of heat transfer enhancement.The disturbed boundary layer and the excited turbulent kinetic energy also contribute much to enhance the heat transfer.In addition,due to the HTE-induced increment of metal tensile strength,the system reliability of lattice channel is better than the conventional one.
基金co-supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (No. 51121004)the Fundamental Research Funds for the Central Universities of China (No. HIT.BRETIV.201315)
文摘Actively cooled thermal protection system has great influence on the engine of a hypersonic vehicle, and it is significant to obtain the thermal and stress distribution in the system. So an analytic estimation and numerical modeling are performed in this paper to investigate the behavior of an actively cooled thermal protection system. The analytic estimation is based on the electric analogy method and finite element analysis（FEA） is applied to the numerical simulation. Temperature and stress distributions are obtained for the actively cooled channel walls with three kinds of nickel alloys with or with no thermal barrier coating（TBC）. The temperature of the channel wall with coating has no obvious difference from the one with no coating, but the stress with coating on the channel wall is much smaller than that with no coating. Inconel X-750 has the best characteristics among the three Ni-based materials due to its higher thermal conductivity, lower elasticity module and greater allowable stress. Analytic estimation and numerical modeling results are compared with each other and a reasonable agreement is obtained.
文摘Transpiration cooling thermal protection systems(TPS)are investigated for potential applications in hypersonic and re-entry vehicles,which are subjected to the severe aerodynamic heating environment.In this paper a transpiration cooling thermal protection system was designed and manufactured,and an experiment platform with radiant heating at the bottom as heat source was developed.The cooling capacity of the transpiration cooling TPS was experimentally investigated.By combining transpiration cooling method with traditional TPS,the heat load capability of the TPS can be improved.The structure temperature with active cooling applied was much lower than that without active cooling applied under the same heat load as well as the heat load increased with active cooling than the one without active cooling for the same structure temperature.The experimental results showed that at 5800 s,the temperature of inner structure was 100°C with active cooling applied compared to 500°C without active cooling applied,then the temperature increased and reached to 360°C at 8300 s.Heat load of this transpiration cooling TPS can be increased by over 70%as compared to the passion one and the cooling capability of the transpiration TPS was about 1700 kJ/kg.The results can provide fundamental data for developing the transpiration cooling TPS.
基金supported by the National Natural Science Foundation of China(No.52373085,U21A2095)Natural Science Foundation of Hubei Province(No.2023AFA828)+3 种基金Innovative Team Program of Natural Science Foundation of Hubei Province(No.2023AFA027)Department of Science and Technology of Hubei Province(No.2024CSA076)Open Fund for Hubei Key Laboratory of Digital Textile Equipment,Wuhan Textile University(No.DTL2023022)National Local Joint Laboratory for Advanced Textile Processing and Clean Production(No.17).
文摘With the increasing global energy consumption and cooling demands,traditional active cooling technologies face inefficiency and environmental challenges.Recently published in Science,a team led by Prof.Hai-bo Zhao has proposed and developed a biomass-based photoluminescent aerogel made from DNA and gelatin to address these challenges.This material achieves a solar-weighted reflectance of over 100%(0.4-0.8μm)and provides a cooling effect of 16.0℃under sunlight.This sustainable material is repairable,recyclable,and biodegradable,offering significant potential for energy-efficient buildings and wearable cooling devices.
基金supported by the National Natural Science Foundation of China(Grant No.52250273)the Tsinghua University Initiative Scientific Research Program。
文摘Active cooling of aircraft skin has garnered significant attention from researchers in recent years due to the increasing flight speeds.The determination of the maximum temperature plays a crucial role in the design of active cooling systems as it dictates the selection of suitable materials for aircraft skin.This research presents two analytical models for predicting surface temperatures in aircraft skin with active cooling channels:one for densely arranged channels and another for sparsely arranged channels.The application criteria of these two models are obtained.The analytical models offer several advantages,including handling non-uniform heat fluxes and providing direct predictions of maximum temperature and its location.Numerical simulations validate these models,demonstrating their accurate estimation capabilities across various solid materials,Reynolds numbers,and thermal conductivities.This investigation lays the foundation for rapid and cost-effective design of optimal cooling channels based on solid thermal conductivity,cooling flow rate,channel spacing,and temperature limits under non-uniform heat flows.Furthermore,an examination of channel aspect ratios reveals that larger ratios result in lower heated surface temperatures.Overall,these analytical temperature prediction models serve as efficient tools for selecting appropriate design parameters for active cooling channels.
基金supported by the National Natural Science Foundation of China(Nos.41801046,42161026)the Natural Science Foundation of Qinghai Province(No.2021-ZJ-716)the Transportation Science and Technology Project of Qinghai Province(No.2019-06&No.2018-02).
文摘Located in the eastern margin of the Tibetan Plateau,the Gonghe-Yushu high-grade highway was the first of its kind in plateau permafrost regions.Most of the road sections along the high-grade highway are unstable or extremely unstable warm permafrost with an average annual ground temperature above−1℃,which is vulnerable to global warming and human engineering activities.This paper describes permafrost characteristics,roadbed design,and operation of the Gonghe-Yushu high-grade highway in detail.It is found that thaw settlement of warm and ice-rich permafrost is the main cause of subgrade subsidence in permafrost sections of this highway due to insufficient permafrost survey and drainage design.It is recommended that the interception and drainage system's design be optimized,and the permafrost upper limit and the variation of ground temperature be further investigated to provide essential data for the treatment of highway distress.It should be emphasized that protecting permafrost soil environment and optimized engineering design are crucial to successful high-grade highway engineering in permafrost regions.
基金sponsored by the National Natural Science Foundation of China (51676163)the National 111 Project under Grant No.B18041。
文摘Active regenerative cooling with supercritical hydrocarbon fuel is considered as the most promising thermal protection method.The existence of buoyancy force would lead to strongly anisotropic flow and thermal transport characteristics.It is closely related to the cooling performance of the engine.To elucidate the mechanisms of turbulent transport,the large eddy simulation(LES) was performed to assess turbulence statistics within different turbulence scales.The results indicated that the buoyancy and inertial force together dominated the change of turbulent structure.Moreover,the spatial thermal buoyancy effect significantly suppressed the vertical velocity fluctuation.This is due to the laminar motion caused by the buoyancy force,thereby weakening the thermal transport.For the statistics of velocity fluctuation,it was found that the buoyancy force and inertial force greatly weaken the vertical and streamwise velocity fluctuation,respectively.For the statistics of thermal transport,the results pointed out that the near-wall heat transport characteristics need to be paid more attention.The thickness of the temperature mixing boundary layer led to the attenuation of vertical heat flux,which inhibited vertical temperature diffusion and predisposed to extreme conditions of heat transfer deterioration.The results can enhance the academic understanding of the heat transfer mechanism of supercritical fluids,and give guidance for further applications of thermal protection.
基金supports provided by Science Center for Gas Turbine Project (P2022-B-Ⅱ-028-001).
文摘The oblique detonation chamber has an extreme high and uneven thermal load due to the fast exothermic combustion process induced by oblique shock wave.The active cooling technology of over-pressure water is an effective thermal protection method with the development of additive manufacturing technology.The realizable κ-ε model coupling with Volume Fraction(VOF) model is applied to solve the boiling flow of cooling water in the mini-channels.The phase transition and heat transfer characteristics are systematically investigated under different pressures.The phase transition process is first observed in the position of oblique detonation wave,and the bubbly flow,the slug flow,the annular flow and the churn flow are captured in the characteristic cooling channel when boiling flow reaching steady stage.In the rear section of the channel,the uneven heat flux distribution of combustion chamber brings to the churn flow,which enhances the heat transfer compared to the annular flow.Compared to the atmospheric water,the appearances of churn flow and annular flow are significantly decreased with the increasing pressure,and they would disappear when the pressure is exceeding 0.5 MPa.The bubbly flow and slug flow play a dominant role when the pressure is higher than 1 MPa,showing that the over-pressure water can significantly enhance the cooling efficiency of the oblique detonation chamber.With the rise of water pressure,the time point of the appearance of phase transition is obviously lagged because of the increasing latent heat of vaporization,and the cooling efficiency is significantly increased due to the simpler phase transition in higher pressure,which means the over-pressure water could withstand longer heat load of oblique detonation engine.
文摘Objective: To study the curative effect of Chinese medicines in treating severe cholestatic hepatitis (SCH).Methods: Three hundred and fifty patients of SCH with total bilirubin level 171 μmol/L were treated with Chinese medicines. Those with Blood Stasis Syndrome were treated with the recipe mainly consisting of Radix Paeoniae Rubra, and those accompanied by blood Heat, fluid retention in the epigastric region, dampness disseminated in Sanjiao ( ) or Yang deficiency of both Spleen and Kidney were treated with recipe modified according to the symptoms and signs.Results: The treatment was markedly effective in 288 cases and effective in 26 cases, the total effective rate being 89.7%.Conclusion: It is difficult to treat severe cholestatic hepatitis, es pecially the chronic cholestatic good effect of Chinese herbal medicine in eliminating jaundice.
