The bench top test is one of the most important and effective methods to evaluate the total thermal protective performance(TPP) of firefighters' protective clothing,which is greatly influenced by the air gaps entr...The bench top test is one of the most important and effective methods to evaluate the total thermal protective performance(TPP) of firefighters' protective clothing,which is greatly influenced by the air gaps entrapped.In this paper,to investigate the effect of air gap width on TPP,a new improved apparatus with two height changeable buttons to hold the thermal sensor was developed to get a series of air gap sizes from 0 mm to 40 mm.The TPP of two types of flame-resistant outer fabrics was measured with TPP test apparatus respectively.Analysis of temperature rise with each air gap width was made to determine the effects of different air gaps on protective performance.It was indicated that air gap size had great effect on TPP of fabrics in the bench top test.An air gap width above 8 mm was suggested for the thermal protective clothing design.展开更多
This paper is to report a prediction model for thermal protective performance of multilayer fabrics based on Matlab neural network toolbox. Then a back propagation (BP) neural network model is developed to predict the...This paper is to report a prediction model for thermal protective performance of multilayer fabrics based on Matlab neural network toolbox. Then a back propagation (BP) neural network model is developed to predict thermal protective performance of multilayer fabrics for firefighters. The network consists of twelve input nodes, six hidden nodes, and one output node. The inputs are weight, thickness, density of warp and weft, limited oxygen index (LOI), and heat conductivity of each-layer fabric. Thermal protective performance (TPP) rating of multilayer fabrics is the output. In this paper, the data from the experiments are used as learning information for the neural network to develop a reliable prediction model. Finnally the model performance is verified, and the proposed model can be applied to predict the thermal protective performance of multilayer fabrics for firefighters.展开更多
Cotton fabrics treated with phase change materials( PCMs)were used in multi-layered fabrics of the fire fighter protective clothing to study its effect on thermal protection. The thermal protective performance( TPP) o...Cotton fabrics treated with phase change materials( PCMs)were used in multi-layered fabrics of the fire fighter protective clothing to study its effect on thermal protection. The thermal protective performance( TPP) of the multi-layered fabrics was measured by a TPP tester under flash fire. Results showed that the utilization of the PCM fabrics improved the thermal protective performance of the multi-layered fabrics. The fabric with a PCM add on of 41. 9% increased the thermal protection by 50. 6% and reduced the time to reach a second degree burn by 8. 4 s compared with the reference fabrics( without PCMs). The employment of the PCM fabrics also reduced the blackened areas on the inner layers. The PCM fabrics with higher PCM melting temperature could bring higher thermal protective performance.展开更多
The large-aperture reflective cameras on the geostationary orbit are susceptible to significant temperature fluctuations due to the“Sun transit”effect.To address the shortcomings of existing thermal control measures...The large-aperture reflective cameras on the geostationary orbit are susceptible to significant temperature fluctuations due to the“Sun transit”effect.To address the shortcomings of existing thermal control measures using camera sunshades to suppress the“Sun transit”and the issue of excessively large solar avoidance angles determined solely by geometric relationships,a thermal control design method is proposed that involves adding multi-layer thermal protection at the secondary mirror position of the camera.The goal is to optimize the avoidance angle and enhance the camera’s tolerance to“Sun transit”.A heat balance and motion relationship between the avoidance angle and duration is established.Then,the minimum solar avoidance angle after adopting the multi-layer thermal protection design is calculated.This angle is compared with the one determined by geometric relationships,leading to the conclusion that this method can effectively enhance the camera’s tolerance to“Sun transit”.A heat dissipation scheme is proposed that involves a coupled north-south heat spreader design with low-temperature compensation for the internal heat source.The calculation results of the two avoidance angles are applied to the calculation of the heat dissipation area and low-temperature compensation power,achieving a closed-loop heat dissipation scheme.Puls,the superiority of the multi-layer thermal protection design method is demonstrated from the perspectives of heat dissipation area and low-temperature compensation power requirements.A comparative analysis of simulation analysis,thermal balance tests,and in-orbit temperature data further validates the effectiveness of this method.展开更多
Thermal runaway(TR)is considered a significant safety hazard for lithium batteries,and thermal protection materials are crucial in mitigating this risk.However,current thermal protection materials generally suffer fro...Thermal runaway(TR)is considered a significant safety hazard for lithium batteries,and thermal protection materials are crucial in mitigating this risk.However,current thermal protection materials generally suffer from poor mechanical properties,flammability,leakage,and rigid crystallization,and they struggle to continuously block excess heat transfer and propagation once thermal saturation occurs.This study proposes a novel type of thermal protection material:an aerogel coupled composite phase change material(CPCM).The composite material consists of gelatin/sodium alginate(Ge/SA)composite biomass aerogel as an insulating component and a thermally induced flexible CPCM made from thermoplastic polyester elastomer as a heat-absorbing component.Inspired by power bank,we coupled the aerogel with CPCM through the binder,so that CPCM can continue to‘charge and store energy’for the aerogel,effectively absorbing heat,delaying the heat saturation phenomenon,and maximizing the duration of thermal insulation.The results demonstrate that the Ge/SA aerogel exhibits excellent thermal insulation(with a temperature difference of approximately 120℃ across a 1 cm thickness)and flame retardancy(achieving a V-0 flame retardant rating).The CPCM exhibits high heat storage density(811.9 J g^(−1)),good thermally induced flexibility(bendable above 40℃),and thermal stability.Furthermore,the Ge/SA-CPCM coupled composite material shows even more outstanding thermal insulation performance,with the top surface temperature remaining at 89℃ after 100 min of exposure to a high temperature of 230℃.This study provides a new direction for the development of TR protection materials for lithium batteries.展开更多
A new thermal protection design method for hypersonic vehicle's leading edge is proposed, which can effectively reduce temperature of the leading edge without additional cooling measures. This method reduces the l...A new thermal protection design method for hypersonic vehicle's leading edge is proposed, which can effectively reduce temperature of the leading edge without additional cooling measures. This method reduces the leading-edge's temperature by the multi-scale collaborative design of the macroscopic thermal optimization and the mesoscopic woven structures of Three-dimensional Orthogonal Woven Ceramic Matrix Composites(TOCMC). The macroscopic thermal optimization is achieved by designing different mesoscopic woven structures in different regions to create combined heat transfer channels to dredge the heat. The combined heat transfer channel is macroscopically represented by the anisotropic thermal conductivity of TOCMC. The thermal optimization multiple linear regression model is established to optimize the heat transport channel, which predicts Theoretical Optimal Thermal Conductivity Configuration(TOTCC) in different regions to achieve the lowest leading-edge temperature. The function-oriented mesostructure design method is invented to design the corresponding mesostructure of TOCMC according to the TOTCC, which consists of universal thermal conductivity prediction formulas for TOCMC. These universal formulas are firstly derived based on the thermal resistance network method, which is verified by experiments with an error of 6.25%. The results show that the collaborative design method can effectively reduce the leading edge temperature by about 12.8% without adding cooling measures.展开更多
The energy equilibrium equation and discrete ordinate methods are combined to establish the one-dimensional steady heat transfer mathematical model of multi-layer thermal insulations （MTIs） in metallic thermal prote...The energy equilibrium equation and discrete ordinate methods are combined to establish the one-dimensional steady heat transfer mathematical model of multi-layer thermal insulations （MTIs） in metallic thermal protection systems. The inverse problem of heat transfer is solved by the genetic algorithm and data from the steady heat transfer experiment of fibrous thermal insulations. The density radiation attenuation coefficient, the albedo of fibrous thermal insulations and the surface emissivity of reflective screens are optimized. Finally, the one-dimensional steady heat transfer model of MTIs with optimized thermal physical parameters is verified by experimental data of the effective MTI conductivity.展开更多
The Solar Close Observations and Proximity Experiments(SCOPE)mission will send a spacecraft into the solar atmosphere at a low altitude of just 5 R☉from the solar center.It aims to elucidate the mechanisms behind sol...The Solar Close Observations and Proximity Experiments(SCOPE)mission will send a spacecraft into the solar atmosphere at a low altitude of just 5 R☉from the solar center.It aims to elucidate the mechanisms behind solar eruptions and coronal heating,and to directly measure the coronal magnetic field.The mission will perform in situ measurements of the current sheet between coronal mass ejections and their associated solar flares,and energetic particles produced by either reconnection or fast-mode shocks driven by coronal mass ejections.This will help to resolve the nature of reconnections in current sheets,and energetic particle acceleration regions.To investigate coronal heating,the mission will observe nano-flares on scales smaller than 70 km in the solar corona and regions smaller than 40 km in the photosphere,where magnetohydrodynamic waves originate.To study solar wind acceleration mechanisms,the mission will also track the process of ion charge-state freezing in the solar wind.A key achievement will be the observation of the coronal magnetic field at unprecedented proximity to the solar photosphere.The polar regions will also be observed at close range,and the inner edge of the solar system dust disk may be identified for the first time.This work presents the detailed background,science,and mission concept of SCOPE and discusses how we aim to address the questions mentioned above.展开更多
Thermal Protection System(TPS)with thick tiles,low thermal conductivity,and a short re-entry stage stands as a critical element within reusable aircraft,whose reliability is related to the function and changes with th...Thermal Protection System(TPS)with thick tiles,low thermal conductivity,and a short re-entry stage stands as a critical element within reusable aircraft,whose reliability is related to the function and changes with their physical properties,external conditions,and degradation.Meanwhile,due to the limitation of testing resources,epistemic uncertainties stemming from the small samples are present in TPS reliability modeling.However,current TPS reliability modeling methods face challenges in characterizing the relationships among reliability and physical properties,external conditions,degradation,and epistemic uncertainties.Therefore,under the framework of belief reliability theory,a TPS reliability model is constructed,which takes into account the physical principle,external conditions,performance degradation,and epistemic uncertainties.A reliability simulation algorithm is proposed to calculate TPS reliability.Through a case study and comparison analysis,the proposed method is validated as more effective than the existing method.Additionally,reliability sensitivity analysis is conducted to identify the sensitive factors of reliability under the condition of small samples,through which suggestions are provided for TPS functional design and improvement.展开更多
Hypersonic vehicles with turbojet, ramjet, and scramjet engines are expected to be widely applied to future transportation systems. Due to high-speed flight in the atmosphere, body outer surfaces suffer strong aerodyn...Hypersonic vehicles with turbojet, ramjet, and scramjet engines are expected to be widely applied to future transportation systems. Due to high-speed flight in the atmosphere, body outer surfaces suffer strong aerodynamic heating, and on the other hand, combustion chamber inter walls are under extremely high temperature and heat flux. Therefore, more efficient and stable active cooling technologies are required in hypersonic vehicles, such as regenerative cooling, film cooling, and transpiration cooling, as well as their combinations. This paper presents a comprehensive literature review on three active cooling methods, i.e., regenerative cooling, film cooling, and transpiration cooling, and deeply analyzes the mechanism of each cooling method, including the fluids flow, heat transfer, and thermal cracking characteristics of different hydrocarbon fuels in regenerative cooling,the heat transfer and flow mechanism of film cooling under supersonic mainstream conditions, and the heat transfer and flow mechanism of transpiration cooling.展开更多
A new idea of drag reduction and thermal protection for hypersonic vehicles is proposed based on the combination of a physical spike and lateral jets for shockreconstruction. The spike recasts the bow shock in front o...A new idea of drag reduction and thermal protection for hypersonic vehicles is proposed based on the combination of a physical spike and lateral jets for shockreconstruction. The spike recasts the bow shock in front of a blunt body into a conical shock, and the lateral jets work to protect the spike tip from overheating and to push the conical shock away from the blunt body when a pitching angle exists during flight. Experiments are conducted in a hypersonic wind tunnel at a nominal Mach number of 6. It is demonstrated that the shock/shock interaction on the blunt body is avoided due to injection and the peak pressure at the reattachment point is reduced by 70% under a 4° attack angle.展开更多
This paper focuses on the usage of the forward-facing cavity and opposing jet combinatorial configuration as the thermal protection system （TPS） for hypersonic vehicles. A hemispherecone nose-tip with the combinator...This paper focuses on the usage of the forward-facing cavity and opposing jet combinatorial configuration as the thermal protection system （TPS） for hypersonic vehicles. A hemispherecone nose-tip with the combinatorial configuration is investigated numerically in hypersonic free stream. Some numerical results are validated by experiments. The flow field parameters, aerodynamic force and surface heat flux distribution are obtained. The influence of the opposing jet stagnation pressure on cooling efficiency of the combinatorial TPS is discussed. The detailed numerical results show that the aerodynamic heating is reduced remarkably by the combinatorial system. The recirculation region plays a pivotal role for the reduction of heat flux. The larger the stagnation pressure of opposing jet is, the more the heating reduction is. This kind of combinatorial system is suitable to be the TPS for the high-speed vehicles which need long-range and long time flight.展开更多
Efficient and accurate strength analysis of bolted connections is essential in analyzing the integral thermal protection system（ITPS） of hypersonic vehicles, since the system bears severe loads and structural failur...Efficient and accurate strength analysis of bolted connections is essential in analyzing the integral thermal protection system（ITPS） of hypersonic vehicles, since the system bears severe loads and structural failures usually occur at the connections. Investigations of composite mechanical properties used in ITPS are still in progress as the architecture of the composites is complex. A new method is proposed in this paper for strength analysis of bolted connections by investigating the elastic behavior and failure strength of three-dimensional C/C orthogonal composites used in ITPS. In this method a multi-scale finite element method incorporating the global–local method is established to ensure high efficiency in macro-scale and precision in meso-scale in analysis.Simulation results reveal that predictions of material properties show reasonable accuracy compared with test results. And the multi-scale method can analyze the strength of connections efficiently and accurately.展开更多
In order to develop further the application of high temperature heat pipe in hypersonic vehicles thermal protection, the principles and characteristics of high temperature heat pipe used in hypersonic vehicles thermal...In order to develop further the application of high temperature heat pipe in hypersonic vehicles thermal protection, the principles and characteristics of high temperature heat pipe used in hypersonic vehicles thermal protection were introduced. The methods of numerical simulation, theory analysis and experiment research were utilized to analyze the frozen start-up and steady state characteristic of the heat pipe as well as the machining improvement for fabricating irregularly shaped heat pipe which is suitable for leading edge of hypersonic vehicles. The results indicate that the frozen start-up time of heat pipe is long （10 min） and there exists large temperature difference along the heat pipe （47 ℃/cm）, but the heat pipe can reduce the temperature in stagnation area of hypersonic vehicles from 1 926 to 982 ℃ and work normally during 1 000-1 200℃. How to improve the maximum heat transfer capability and reduce the time needed for start-up from frozen state of the heat pipe by optimizing thermostructure such as designing of a novel wick with high performance is the key point in hypersonic vehicles thermal protection of heat pipe.展开更多
Various thermal protection materials exhibit obviously different and complicated thermal response,oxidation and ablation behavior,which are very important for the appropriate design and selection.However,the relative ...Various thermal protection materials exhibit obviously different and complicated thermal response,oxidation and ablation behavior,which are very important for the appropriate design and selection.However,the relative researches are very few currently.In this work,the thermal response,oxidation and ablation behavior of representative thermal protection materials including ultra-high temperature ceramics,C/SiC,C/C, graphite and graphite-ceramic were investigated systematically in strong heat flux,high enthalpy and low-pressure environments.Thermal response of these materials was analyzed based on experimental results and thermal energy balance that accounts for all of the heat transfer processes transporting energy into and out of the surface.Many factors were playing important roles in the thermal response including thermal conductivity,volumetric heat capacity,catalytic efficiency,emissivity and oxidation characteristics of the materials.The importance of each factor not only depends on the material characteristics such as material composition and phase content but also environment parameters including heat flux,enthalpy,pressure and testing time.The comparisons and relationships of oxidation and ablation behaviors for these materials under extreme environments were also illustrated in detail.Furthermore,thermal response and ablation behaviors of pre-oxidized material or repeated tests were also performed to evaluate the effect of pre-treatment on the performance and reusability of thermal protection materials.This work offers guiding significance for the appropriate design and selection of thermal protection materials.展开更多
Silica-based materials are widely employed in the thermal protection system for hypersonic vehicles, and the investigation of their catalytic characteristics is crucially important for accurate aerothermal heating pre...Silica-based materials are widely employed in the thermal protection system for hypersonic vehicles, and the investigation of their catalytic characteristics is crucially important for accurate aerothermal heating prediction. By analyzing the disadvantages of Norman＇s high and low temperature models, this paper combines the two models and proposes an eight-reaction combined surface catalytic model to describe the catalysis between oxygen and silica surface. Given proper evaluation of the parameters according to many references, the recombination coefficient obtained shows good agreement with experimental data. The catalytic mechanisms between oxygen and silica surface are then analyzed. Results show that with the increase of the wall temperature, the dominant reaction contributing to catalytic coefficient varies from Langmuir Hinshelwood （LH） recombination （Tw 〈 620 K） to Eley Rideal （ER） replacement （620 K 〈 Tw 〈 1350 K）, and then to 02 desorption （Tw 〉 1350 K）. The surface coverage of chemisorption areas varies evidently with the dominant reactions in the high temperature （HT） range, while the surface coverage of physisorption areas varies within quite low temperature （LT） range （Tw 〈 250 K）. Recommended evaluation of partial parameters is also given.展开更多
The three-dimensional Navier Stokes equation and the k-ε viscous model are used to simulate the attack angle characteristics of a hemisphere nose-tip with an opposing jet thermal protection system in supersonic flow ...The three-dimensional Navier Stokes equation and the k-ε viscous model are used to simulate the attack angle characteristics of a hemisphere nose-tip with an opposing jet thermal protection system in supersonic flow conditions. The numerical method is validated by the relevant experiment. The flow field parameters, aerodynamic forces, and surface heat flux distributions for attack angles of 0°, 2°, 5°, 7°, and 10° are obtained. The detailed numerical results show that the cruise attack angle has a great influence on the flow field parameters, aerodynamic force, and surface heat flux distribution of the supersonic vehicle nose-tip with an opposing jet thermal protection system. When the attack angle reaches 10°, the heat flux on the windward generatrix is close to the maximal heat flux on the wall surface of the nose-tip without thermal protection system, thus the thermal protection has failed.展开更多
Hypersonic vehicles represent future trends of military equipments and play an important role in future war. Thermal protection materials and structures, Which relate to the safety of hypersonic vehicles, are one of t...Hypersonic vehicles represent future trends of military equipments and play an important role in future war. Thermal protection materials and structures, Which relate to the safety of hypersonic vehicles, are one of the most key techniques in design and manufacture of hypersonic vehicles. Among these materials and Structures, such as metallic temperature protection structure, the temperature ceramics and carbon/carbon composites are usually adopted in design. The recent progresses of research and applica- tion of ultra-high temperature materials in preparation, oxidation resistance, mechanical and physical characterization are summarized.展开更多
The new regenerative cooling thermal protection system exhibits the multifunctional characteristics of load-carrying and heat exchange cooling,which are fundamental for the lightweight design and thermal protection of...The new regenerative cooling thermal protection system exhibits the multifunctional characteristics of load-carrying and heat exchange cooling,which are fundamental for the lightweight design and thermal protection of hypersonic vehicles.Triply periodic minimal surface(TPMS)is especially suitable for the structural design of the internal cavity of regenerative cooling structures owing to its excellent structural characteristics.In this study,test pieces were manufactured using Ti6Al4V lightweight material.We designed three types of porous test pieces,and the interior was filled with a TPMS lattice(Gyroid,Primitive,I-WP)with a porosity of 30%.All porous test pieces were manufactured via selective laser melting technology.A combination of experiments and finite element simulations were performed to study the selection of the internal cavity structure of the regenerative cooling thermal protection system.Hence,the relationship between the geometry and mechanical properties of a unit cell is established,and the deformation mechanism of the porous unit cell is clarified.Among the three types of porous test pieces,the weight of the test piece filled with the Gyroid unit cell was reduced by 8.21%,the average tensile strength was reduced by 17.7%compared to the solid test piece,while the average tensile strength of the Primitive and I-WP porous test pieces were decreased by 30.5%and 33.3%,respectively.Compared with the other two types of unit cells,Gyroid exhibited better mechanical conductivity characteristics.Its deformation process was characterised by stretching,shearing,and twisting,while the Primitive and I-WP unit cells underwent tensile deformation and tensile and shear deformation,respectively.The finite element predictions in the study agree well with the experimental results.The results can provide a basis for the design of regenerative cooling thermal protection system.展开更多
The thermal protection materials and structures are widely used in hypersonic vehicles for the purpose of thermal insulation, and their mechanical behavior is one of the key issues in design and manufacture of hyperso...The thermal protection materials and structures are widely used in hypersonic vehicles for the purpose of thermal insulation, and their mechanical behavior is one of the key issues in design and manufacture of hypersonic vehicles. It is our great pleasure to present the seven papers in this special subject of Theoretical ＆ Applied Mechanics Letters （TAML） and introduce the recent progresses on the mechanical behavior of thermal protection materials and structures by the authors.展开更多
基金National Natural Science Foundation of China (No. 50876019)the Research Fund for the Doctoral Program of Higher Education of China (No. 200802550009)Fundamental Research Funds for the Central Universities,China
文摘The bench top test is one of the most important and effective methods to evaluate the total thermal protective performance(TPP) of firefighters' protective clothing,which is greatly influenced by the air gaps entrapped.In this paper,to investigate the effect of air gap width on TPP,a new improved apparatus with two height changeable buttons to hold the thermal sensor was developed to get a series of air gap sizes from 0 mm to 40 mm.The TPP of two types of flame-resistant outer fabrics was measured with TPP test apparatus respectively.Analysis of temperature rise with each air gap width was made to determine the effects of different air gaps on protective performance.It was indicated that air gap size had great effect on TPP of fabrics in the bench top test.An air gap width above 8 mm was suggested for the thermal protective clothing design.
文摘This paper is to report a prediction model for thermal protective performance of multilayer fabrics based on Matlab neural network toolbox. Then a back propagation (BP) neural network model is developed to predict thermal protective performance of multilayer fabrics for firefighters. The network consists of twelve input nodes, six hidden nodes, and one output node. The inputs are weight, thickness, density of warp and weft, limited oxygen index (LOI), and heat conductivity of each-layer fabric. Thermal protective performance (TPP) rating of multilayer fabrics is the output. In this paper, the data from the experiments are used as learning information for the neural network to develop a reliable prediction model. Finnally the model performance is verified, and the proposed model can be applied to predict the thermal protective performance of multilayer fabrics for firefighters.
基金Fundamental Research Funds for the Central Universities,China(No.14D110715/17/18)Start up Fund by Shanghai University of Engineering Science(No.2015-69)Young Teacher Training Program by Shanghai,China(No.ZZGCD15051))
文摘Cotton fabrics treated with phase change materials( PCMs)were used in multi-layered fabrics of the fire fighter protective clothing to study its effect on thermal protection. The thermal protective performance( TPP) of the multi-layered fabrics was measured by a TPP tester under flash fire. Results showed that the utilization of the PCM fabrics improved the thermal protective performance of the multi-layered fabrics. The fabric with a PCM add on of 41. 9% increased the thermal protection by 50. 6% and reduced the time to reach a second degree burn by 8. 4 s compared with the reference fabrics( without PCMs). The employment of the PCM fabrics also reduced the blackened areas on the inner layers. The PCM fabrics with higher PCM melting temperature could bring higher thermal protective performance.
基金supported by the Na⁃tional Key Research and Development Program of China(No.2021YFC2202102)。
文摘The large-aperture reflective cameras on the geostationary orbit are susceptible to significant temperature fluctuations due to the“Sun transit”effect.To address the shortcomings of existing thermal control measures using camera sunshades to suppress the“Sun transit”and the issue of excessively large solar avoidance angles determined solely by geometric relationships,a thermal control design method is proposed that involves adding multi-layer thermal protection at the secondary mirror position of the camera.The goal is to optimize the avoidance angle and enhance the camera’s tolerance to“Sun transit”.A heat balance and motion relationship between the avoidance angle and duration is established.Then,the minimum solar avoidance angle after adopting the multi-layer thermal protection design is calculated.This angle is compared with the one determined by geometric relationships,leading to the conclusion that this method can effectively enhance the camera’s tolerance to“Sun transit”.A heat dissipation scheme is proposed that involves a coupled north-south heat spreader design with low-temperature compensation for the internal heat source.The calculation results of the two avoidance angles are applied to the calculation of the heat dissipation area and low-temperature compensation power,achieving a closed-loop heat dissipation scheme.Puls,the superiority of the multi-layer thermal protection design method is demonstrated from the perspectives of heat dissipation area and low-temperature compensation power requirements.A comparative analysis of simulation analysis,thermal balance tests,and in-orbit temperature data further validates the effectiveness of this method.
基金supported by the National Key Research and Development Program of China(2022YFB3806501)the National Natural Science Foundation of China(22178050,22108026)+3 种基金the Young Elite Scientists Sponsorship Program by CAST(2021QNRC001)the Natural Science Foundation of Liaoning Province(2022-BS-091)the Dalian Science and Technology Innovation Fund Young Tech Star(2022RQ008)the Fundamental Research Funds for the Central Universities(DUT22LAB610).
文摘Thermal runaway(TR)is considered a significant safety hazard for lithium batteries,and thermal protection materials are crucial in mitigating this risk.However,current thermal protection materials generally suffer from poor mechanical properties,flammability,leakage,and rigid crystallization,and they struggle to continuously block excess heat transfer and propagation once thermal saturation occurs.This study proposes a novel type of thermal protection material:an aerogel coupled composite phase change material(CPCM).The composite material consists of gelatin/sodium alginate(Ge/SA)composite biomass aerogel as an insulating component and a thermally induced flexible CPCM made from thermoplastic polyester elastomer as a heat-absorbing component.Inspired by power bank,we coupled the aerogel with CPCM through the binder,so that CPCM can continue to‘charge and store energy’for the aerogel,effectively absorbing heat,delaying the heat saturation phenomenon,and maximizing the duration of thermal insulation.The results demonstrate that the Ge/SA aerogel exhibits excellent thermal insulation(with a temperature difference of approximately 120℃ across a 1 cm thickness)and flame retardancy(achieving a V-0 flame retardant rating).The CPCM exhibits high heat storage density(811.9 J g^(−1)),good thermally induced flexibility(bendable above 40℃),and thermal stability.Furthermore,the Ge/SA-CPCM coupled composite material shows even more outstanding thermal insulation performance,with the top surface temperature remaining at 89℃ after 100 min of exposure to a high temperature of 230℃.This study provides a new direction for the development of TR protection materials for lithium batteries.
基金co-supported by the Science Center for Gas Turbine Project, China (No. P2022-B-Ⅱ-025-001)the National Science and Technology Major Project, China (No. Y2019-Ⅰ-0018-0017)。
文摘A new thermal protection design method for hypersonic vehicle's leading edge is proposed, which can effectively reduce temperature of the leading edge without additional cooling measures. This method reduces the leading-edge's temperature by the multi-scale collaborative design of the macroscopic thermal optimization and the mesoscopic woven structures of Three-dimensional Orthogonal Woven Ceramic Matrix Composites(TOCMC). The macroscopic thermal optimization is achieved by designing different mesoscopic woven structures in different regions to create combined heat transfer channels to dredge the heat. The combined heat transfer channel is macroscopically represented by the anisotropic thermal conductivity of TOCMC. The thermal optimization multiple linear regression model is established to optimize the heat transport channel, which predicts Theoretical Optimal Thermal Conductivity Configuration(TOTCC) in different regions to achieve the lowest leading-edge temperature. The function-oriented mesostructure design method is invented to design the corresponding mesostructure of TOCMC according to the TOTCC, which consists of universal thermal conductivity prediction formulas for TOCMC. These universal formulas are firstly derived based on the thermal resistance network method, which is verified by experiments with an error of 6.25%. The results show that the collaborative design method can effectively reduce the leading edge temperature by about 12.8% without adding cooling measures.
文摘The energy equilibrium equation and discrete ordinate methods are combined to establish the one-dimensional steady heat transfer mathematical model of multi-layer thermal insulations （MTIs） in metallic thermal protection systems. The inverse problem of heat transfer is solved by the genetic algorithm and data from the steady heat transfer experiment of fibrous thermal insulations. The density radiation attenuation coefficient, the albedo of fibrous thermal insulations and the surface emissivity of reflective screens are optimized. Finally, the one-dimensional steady heat transfer model of MTIs with optimized thermal physical parameters is verified by experimental data of the effective MTI conductivity.
基金supported by the National Key R&D Program of China (2022YFF0503800)National Natural Science Foundation of China grants (12073073, 11933009, 12273107 and U2031141)+6 种基金grants associated with the Yunnan Revitalization Talent Support Programthe Foundation of the Chinese Academy of Sciences (Light of West China Program)the Yunling Scholar Project of Yunnan Provincethe Yunnan Province Scientist Workshop of Solar Physicsthe Applied Basic Research of Yunnan Province grants (202101AT070018 and 2019FB005)supported by the National Natural Science Foundation of China grants (12273107 and U2031141)the Yunnan Key Laboratory of Solar Physics and Space Science (202205AG070009)
文摘The Solar Close Observations and Proximity Experiments(SCOPE)mission will send a spacecraft into the solar atmosphere at a low altitude of just 5 R☉from the solar center.It aims to elucidate the mechanisms behind solar eruptions and coronal heating,and to directly measure the coronal magnetic field.The mission will perform in situ measurements of the current sheet between coronal mass ejections and their associated solar flares,and energetic particles produced by either reconnection or fast-mode shocks driven by coronal mass ejections.This will help to resolve the nature of reconnections in current sheets,and energetic particle acceleration regions.To investigate coronal heating,the mission will observe nano-flares on scales smaller than 70 km in the solar corona and regions smaller than 40 km in the photosphere,where magnetohydrodynamic waves originate.To study solar wind acceleration mechanisms,the mission will also track the process of ion charge-state freezing in the solar wind.A key achievement will be the observation of the coronal magnetic field at unprecedented proximity to the solar photosphere.The polar regions will also be observed at close range,and the inner edge of the solar system dust disk may be identified for the first time.This work presents the detailed background,science,and mission concept of SCOPE and discusses how we aim to address the questions mentioned above.
基金supported by the steady supports scientific research of Key Laboratory of Defense Science and Technology,China(No.WDZC20220105)the National Natural Science Foundation of China(Nos.51775020,62073009,U20B2002)the Science Challenge Project,China(No.TZ2018007)。
文摘Thermal Protection System(TPS)with thick tiles,low thermal conductivity,and a short re-entry stage stands as a critical element within reusable aircraft,whose reliability is related to the function and changes with their physical properties,external conditions,and degradation.Meanwhile,due to the limitation of testing resources,epistemic uncertainties stemming from the small samples are present in TPS reliability modeling.However,current TPS reliability modeling methods face challenges in characterizing the relationships among reliability and physical properties,external conditions,degradation,and epistemic uncertainties.Therefore,under the framework of belief reliability theory,a TPS reliability model is constructed,which takes into account the physical principle,external conditions,performance degradation,and epistemic uncertainties.A reliability simulation algorithm is proposed to calculate TPS reliability.Through a case study and comparison analysis,the proposed method is validated as more effective than the existing method.Additionally,reliability sensitivity analysis is conducted to identify the sensitive factors of reliability under the condition of small samples,through which suggestions are provided for TPS functional design and improvement.
基金co-supported by the National Natural Science Foundation of China (No. 51536004)the Science Fund for Creative Research Groups of NSFC (No. 51621062)
文摘Hypersonic vehicles with turbojet, ramjet, and scramjet engines are expected to be widely applied to future transportation systems. Due to high-speed flight in the atmosphere, body outer surfaces suffer strong aerodynamic heating, and on the other hand, combustion chamber inter walls are under extremely high temperature and heat flux. Therefore, more efficient and stable active cooling technologies are required in hypersonic vehicles, such as regenerative cooling, film cooling, and transpiration cooling, as well as their combinations. This paper presents a comprehensive literature review on three active cooling methods, i.e., regenerative cooling, film cooling, and transpiration cooling, and deeply analyzes the mechanism of each cooling method, including the fluids flow, heat transfer, and thermal cracking characteristics of different hydrocarbon fuels in regenerative cooling,the heat transfer and flow mechanism of film cooling under supersonic mainstream conditions, and the heat transfer and flow mechanism of transpiration cooling.
基金the National Natural Science Foundation of China (10632090)the National Aerodynamic Pre-Research Foundation (513130401)
文摘A new idea of drag reduction and thermal protection for hypersonic vehicles is proposed based on the combination of a physical spike and lateral jets for shockreconstruction. The spike recasts the bow shock in front of a blunt body into a conical shock, and the lateral jets work to protect the spike tip from overheating and to push the conical shock away from the blunt body when a pitching angle exists during flight. Experiments are conducted in a hypersonic wind tunnel at a nominal Mach number of 6. It is demonstrated that the shock/shock interaction on the blunt body is avoided due to injection and the peak pressure at the reattachment point is reduced by 70% under a 4° attack angle.
基金co-supported by National Natural Science Foundation of China (No. 90916018)Research Fund for the Doctoral Program of Higher Education of China (No.200899980006)
文摘This paper focuses on the usage of the forward-facing cavity and opposing jet combinatorial configuration as the thermal protection system （TPS） for hypersonic vehicles. A hemispherecone nose-tip with the combinatorial configuration is investigated numerically in hypersonic free stream. Some numerical results are validated by experiments. The flow field parameters, aerodynamic force and surface heat flux distribution are obtained. The influence of the opposing jet stagnation pressure on cooling efficiency of the combinatorial TPS is discussed. The detailed numerical results show that the aerodynamic heating is reduced remarkably by the combinatorial system. The recirculation region plays a pivotal role for the reduction of heat flux. The larger the stagnation pressure of opposing jet is, the more the heating reduction is. This kind of combinatorial system is suitable to be the TPS for the high-speed vehicles which need long-range and long time flight.
基金co-supported by the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe National Natural Science Foundation of China (No. 11302105)
文摘Efficient and accurate strength analysis of bolted connections is essential in analyzing the integral thermal protection system（ITPS） of hypersonic vehicles, since the system bears severe loads and structural failures usually occur at the connections. Investigations of composite mechanical properties used in ITPS are still in progress as the architecture of the composites is complex. A new method is proposed in this paper for strength analysis of bolted connections by investigating the elastic behavior and failure strength of three-dimensional C/C orthogonal composites used in ITPS. In this method a multi-scale finite element method incorporating the global–local method is established to ensure high efficiency in macro-scale and precision in meso-scale in analysis.Simulation results reveal that predictions of material properties show reasonable accuracy compared with test results. And the multi-scale method can analyze the strength of connections efficiently and accurately.
基金Project(51076062) supported by the National Natural Science Foundation of China
文摘In order to develop further the application of high temperature heat pipe in hypersonic vehicles thermal protection, the principles and characteristics of high temperature heat pipe used in hypersonic vehicles thermal protection were introduced. The methods of numerical simulation, theory analysis and experiment research were utilized to analyze the frozen start-up and steady state characteristic of the heat pipe as well as the machining improvement for fabricating irregularly shaped heat pipe which is suitable for leading edge of hypersonic vehicles. The results indicate that the frozen start-up time of heat pipe is long （10 min） and there exists large temperature difference along the heat pipe （47 ℃/cm）, but the heat pipe can reduce the temperature in stagnation area of hypersonic vehicles from 1 926 to 982 ℃ and work normally during 1 000-1 200℃. How to improve the maximum heat transfer capability and reduce the time needed for start-up from frozen state of the heat pipe by optimizing thermostructure such as designing of a novel wick with high performance is the key point in hypersonic vehicles thermal protection of heat pipe.
基金supported by Key Program of National Natural Science Foundation of China (No. 52032003)National Natural Science for Youth Foundation of China (No. 52102093)+2 种基金National Natural Science Foundation of China (No. 51872059),National Natural Science Foundation of China (No. 51772061)China Postdoctoral Science Foundation (No. 2021M690817)Heilongjiang Provincial Postdoctoral Science Foundation (No. LBH-Z20144)。
文摘Various thermal protection materials exhibit obviously different and complicated thermal response,oxidation and ablation behavior,which are very important for the appropriate design and selection.However,the relative researches are very few currently.In this work,the thermal response,oxidation and ablation behavior of representative thermal protection materials including ultra-high temperature ceramics,C/SiC,C/C, graphite and graphite-ceramic were investigated systematically in strong heat flux,high enthalpy and low-pressure environments.Thermal response of these materials was analyzed based on experimental results and thermal energy balance that accounts for all of the heat transfer processes transporting energy into and out of the surface.Many factors were playing important roles in the thermal response including thermal conductivity,volumetric heat capacity,catalytic efficiency,emissivity and oxidation characteristics of the materials.The importance of each factor not only depends on the material characteristics such as material composition and phase content but also environment parameters including heat flux,enthalpy,pressure and testing time.The comparisons and relationships of oxidation and ablation behaviors for these materials under extreme environments were also illustrated in detail.Furthermore,thermal response and ablation behaviors of pre-oxidized material or repeated tests were also performed to evaluate the effect of pre-treatment on the performance and reusability of thermal protection materials.This work offers guiding significance for the appropriate design and selection of thermal protection materials.
基金co-supported by the National Natural Science Foundation of China (No. 51306204)the Natural Science Foundation of Hunan Province (No. 13JJ2002)
文摘Silica-based materials are widely employed in the thermal protection system for hypersonic vehicles, and the investigation of their catalytic characteristics is crucially important for accurate aerothermal heating prediction. By analyzing the disadvantages of Norman＇s high and low temperature models, this paper combines the two models and proposes an eight-reaction combined surface catalytic model to describe the catalysis between oxygen and silica surface. Given proper evaluation of the parameters according to many references, the recombination coefficient obtained shows good agreement with experimental data. The catalytic mechanisms between oxygen and silica surface are then analyzed. Results show that with the increase of the wall temperature, the dominant reaction contributing to catalytic coefficient varies from Langmuir Hinshelwood （LH） recombination （Tw 〈 620 K） to Eley Rideal （ER） replacement （620 K 〈 Tw 〈 1350 K）, and then to 02 desorption （Tw 〉 1350 K）. The surface coverage of chemisorption areas varies evidently with the dominant reactions in the high temperature （HT） range, while the surface coverage of physisorption areas varies within quite low temperature （LT） range （Tw 〈 250 K）. Recommended evaluation of partial parameters is also given.
基金Project supported by the National Natural Science Foundation of China (Grant No. 90916018)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 200899980006)the Natural Science Foundation of Hunan Province,China(Grant No. 09JJ3109)
文摘The three-dimensional Navier Stokes equation and the k-ε viscous model are used to simulate the attack angle characteristics of a hemisphere nose-tip with an opposing jet thermal protection system in supersonic flow conditions. The numerical method is validated by the relevant experiment. The flow field parameters, aerodynamic forces, and surface heat flux distributions for attack angles of 0°, 2°, 5°, 7°, and 10° are obtained. The detailed numerical results show that the cruise attack angle has a great influence on the flow field parameters, aerodynamic force, and surface heat flux distribution of the supersonic vehicle nose-tip with an opposing jet thermal protection system. When the attack angle reaches 10°, the heat flux on the windward generatrix is close to the maximal heat flux on the wall surface of the nose-tip without thermal protection system, thus the thermal protection has failed.
文摘Hypersonic vehicles represent future trends of military equipments and play an important role in future war. Thermal protection materials and structures, Which relate to the safety of hypersonic vehicles, are one of the most key techniques in design and manufacture of hypersonic vehicles. Among these materials and Structures, such as metallic temperature protection structure, the temperature ceramics and carbon/carbon composites are usually adopted in design. The recent progresses of research and applica- tion of ultra-high temperature materials in preparation, oxidation resistance, mechanical and physical characterization are summarized.
基金support from the National Natural Science Foundation of China(NSFC,Project Nos.91860136 and 51801231)the Key R&D Plan of Guangdong Province(Grant No.2018B090905001)the Key Science and Technology project of Shaanxi Province(Grant No.2018zdzx01-04-01).
文摘The new regenerative cooling thermal protection system exhibits the multifunctional characteristics of load-carrying and heat exchange cooling,which are fundamental for the lightweight design and thermal protection of hypersonic vehicles.Triply periodic minimal surface(TPMS)is especially suitable for the structural design of the internal cavity of regenerative cooling structures owing to its excellent structural characteristics.In this study,test pieces were manufactured using Ti6Al4V lightweight material.We designed three types of porous test pieces,and the interior was filled with a TPMS lattice(Gyroid,Primitive,I-WP)with a porosity of 30%.All porous test pieces were manufactured via selective laser melting technology.A combination of experiments and finite element simulations were performed to study the selection of the internal cavity structure of the regenerative cooling thermal protection system.Hence,the relationship between the geometry and mechanical properties of a unit cell is established,and the deformation mechanism of the porous unit cell is clarified.Among the three types of porous test pieces,the weight of the test piece filled with the Gyroid unit cell was reduced by 8.21%,the average tensile strength was reduced by 17.7%compared to the solid test piece,while the average tensile strength of the Primitive and I-WP porous test pieces were decreased by 30.5%and 33.3%,respectively.Compared with the other two types of unit cells,Gyroid exhibited better mechanical conductivity characteristics.Its deformation process was characterised by stretching,shearing,and twisting,while the Primitive and I-WP unit cells underwent tensile deformation and tensile and shear deformation,respectively.The finite element predictions in the study agree well with the experimental results.The results can provide a basis for the design of regenerative cooling thermal protection system.
基金support from the Natural Science Foundation of China(91016029,91216302,and 91216301)
文摘The thermal protection materials and structures are widely used in hypersonic vehicles for the purpose of thermal insulation, and their mechanical behavior is one of the key issues in design and manufacture of hypersonic vehicles. It is our great pleasure to present the seven papers in this special subject of Theoretical ＆ Applied Mechanics Letters （TAML） and introduce the recent progresses on the mechanical behavior of thermal protection materials and structures by the authors.
