More than half of the total length of the Qinghai-Tibet Railroad (QTR) traverses warm (0 to-1 ℃) permafrost areas, and about 40% of its total length is in ice-rich permafrost areas. The construction of the QTR also m...More than half of the total length of the Qinghai-Tibet Railroad (QTR) traverses warm (0 to-1 ℃) permafrost areas, and about 40% of its total length is in ice-rich permafrost areas. The construction of the QTR also must consider the impacts of climatic warming along the QTR during the next 50～100 years. The latest projection indicates a warming of 2.2 to 2.6 ℃ on the Qinghai-Tibet Plateau (QTP) by the year 2050. Therefore, the key to the successful construction of the QTR is to protect permafrost from being thawed. Although railroad construction in permafrost areas has had a history of more than 100 years, the troubled sections of the railroads in permafrost areas have been greater than 30% of their total length. Based on the experiences and lessons learned from the road construction in permafrost areas, both in China and abroad, the author proposes that the principle of'active cooling'of railroad roadbed by lowering permafrost temperatures should be used in designing QTR, rather than that of'passive protection' of permafrost through increasing thermal resistance of roadway, such as increasing fill thickness and/or using insulative materials. This is especially important for the road sections in warm, ice-rich permafrost. In addition, this paper proposes several methods for'cooling the roadbed' by controlling radiation, convection and conduction through modifying roadway structure and using different fill materials.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...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
基金This work was supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX SW 04)
文摘More than half of the total length of the Qinghai-Tibet Railroad (QTR) traverses warm (0 to-1 ℃) permafrost areas, and about 40% of its total length is in ice-rich permafrost areas. The construction of the QTR also must consider the impacts of climatic warming along the QTR during the next 50～100 years. The latest projection indicates a warming of 2.2 to 2.6 ℃ on the Qinghai-Tibet Plateau (QTP) by the year 2050. Therefore, the key to the successful construction of the QTR is to protect permafrost from being thawed. Although railroad construction in permafrost areas has had a history of more than 100 years, the troubled sections of the railroads in permafrost areas have been greater than 30% of their total length. Based on the experiences and lessons learned from the road construction in permafrost areas, both in China and abroad, the author proposes that the principle of'active cooling'of railroad roadbed by lowering permafrost temperatures should be used in designing QTR, rather than that of'passive protection' of permafrost through increasing thermal resistance of roadway, such as increasing fill thickness and/or using insulative materials. This is especially important for the road sections in warm, ice-rich permafrost. In addition, this paper proposes several methods for'cooling the roadbed' by controlling radiation, convection and conduction through modifying roadway structure and using different fill materials.
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.
