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
The temperature response calculation of thermal protection materials,especially ablative thermal protection materials,usually adopts the ablation model,which is complicated in process and requires a large amount of ca...The temperature response calculation of thermal protection materials,especially ablative thermal protection materials,usually adopts the ablation model,which is complicated in process and requires a large amount of calculation.Especially in the process of optimization calculation and parameter identification,the ablation model needs to be called many times,so it is necessary to construct an ablation surrogate model to improve the computational efficiency under the premise of ensuring the accuracy.In this paper,the Gaussian process model method is used to construct a thermal protection material ablation surrogate model,and the prediction accuracy of the surrogate model is improved through optimization.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
Safety issue is still a problem nowadays for the large-scale application of lithium-ion batteries(LIBs)in electric vehicles and energy storage stations.The unsafe behaviors of LIBs arise from the thermal run-away,whic...Safety issue is still a problem nowadays for the large-scale application of lithium-ion batteries(LIBs)in electric vehicles and energy storage stations.The unsafe behaviors of LIBs arise from the thermal run-away,which is intrinsically triggered by the overcharging and overheating.To improve the safety of LIBs,various protection strategies based on self-actuating reaction control mechanisms(SRCMs)have been proposed,including redox shuttle,polymerizable monomer additive,potential-sensitive separator,thermal shutdown separator,positive-temperature-coefficient electrode,thermally polymerizable addi-tive,and reversible thermal phase transition electrolyte.As build-in protection mechanisms,these meth-ods can sensitively detect either the temperature change inside battery or the potential change of the electrode,and spontaneously shut down the electrode reaction at risky conditions,thus preventing the battery from going into thermal runaway.Given their advantages in enhancing the intrinsic safety of LIBs,this paper overviews the research progresses of SRCMs after a brief introduction of thermal runaway mechanism and limitations of conventional thermal runaway mitigating measures.More importantly,the current states and issues,key challenges,and future developing trends of SRCTs are also discussed and outlined from the viewpoint of practical application,aiming at providing insights and guidance for developing more effective SRCMs for LIBs.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
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.
基金supported by Independent Research and Development Project of CASC(YF-ZZYF-2022-132)。
文摘The temperature response calculation of thermal protection materials,especially ablative thermal protection materials,usually adopts the ablation model,which is complicated in process and requires a large amount of calculation.Especially in the process of optimization calculation and parameter identification,the ablation model needs to be called many times,so it is necessary to construct an ablation surrogate model to improve the computational efficiency under the premise of ensuring the accuracy.In this paper,the Gaussian process model method is used to construct a thermal protection material ablation surrogate model,and the prediction accuracy of the surrogate model is improved through optimization.
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financially supported by the National Natural Science Foundation of China(U22A20438)the National Key R&D Program of China(2022YFB2502100)the National Natural Science Foundation of China(22309138).
文摘Safety issue is still a problem nowadays for the large-scale application of lithium-ion batteries(LIBs)in electric vehicles and energy storage stations.The unsafe behaviors of LIBs arise from the thermal run-away,which is intrinsically triggered by the overcharging and overheating.To improve the safety of LIBs,various protection strategies based on self-actuating reaction control mechanisms(SRCMs)have been proposed,including redox shuttle,polymerizable monomer additive,potential-sensitive separator,thermal shutdown separator,positive-temperature-coefficient electrode,thermally polymerizable addi-tive,and reversible thermal phase transition electrolyte.As build-in protection mechanisms,these meth-ods can sensitively detect either the temperature change inside battery or the potential change of the electrode,and spontaneously shut down the electrode reaction at risky conditions,thus preventing the battery from going into thermal runaway.Given their advantages in enhancing the intrinsic safety of LIBs,this paper overviews the research progresses of SRCMs after a brief introduction of thermal runaway mechanism and limitations of conventional thermal runaway mitigating measures.More importantly,the current states and issues,key challenges,and future developing trends of SRCTs are also discussed and outlined from the viewpoint of practical application,aiming at providing insights and guidance for developing more effective SRCMs for LIBs.
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.
