针对飞行器高超声速飞行时严重的气动加热环境,提出疏导式热防护结构(TPS),为飞行器前缘提供热防护。采用有限元法和有限体积法,分别对在特定工况下飞行的尖化前缘固体域和流体域进行计算,验证了前缘内嵌高导热材料的防热效果,其中来流马赫数为6.5时,头部壁面最高温度下降了13.6%,尾部最低温度升高了16.7%,实现了热流由高温区向低温区的转移,削弱了前缘头部的热载荷,强化了前缘的热防护能力。对于耐热材料提出一个最佳厚度值,即综合考虑厚度增加带来额外的热载荷,在保证热结构稳定的同时选取最小厚度。对耐热材料黑度和高导热材料的导热系数对壁面温度的影响进行了讨论,为尖化前缘防热材料的选取提供了一定的参考依据。
The structure of leading thermal protection is considered as thermal protection system (TPS) to prevent hypersonic vehicle from the serious aerodynamic heating. By the use of finite element method and finite volume method, we calculate the solid domain and fluid domain of sharp leading-edge which is flying under given conditions. And it is proved that high thermal conductivity materials which are embedded in the leading-edge have an effect on thermal protection. The maximum temperature of the head decreases by 13.6%, and the minimum temperature of after-body increases by 16.7% when Mach number is 6.5. The transfer of heat from head to after-body is achieved, the front head of the thermal load is weakened and the ability of leading-edge thermal protection is strengthened. Considering that heat loading increases with increase of thickness, we propose the optimal thickness value of heat-resistant material which is the minimum value that can ensure the thermal structural stability of sharp leading-edge. The effects of black level of heat-resistant materials and thermal conductivity of high-conductivity materials on the wall temperature are discussed, which provides some references for the selection of thermal protection materials of sharp leading-edge.
[1] Glass D E. Ceramic matrix composite (CMC) thermal protection system (TPS) and hot structures for hypersonic vehicles. AIAA-2008-2068, 2008.
[2] 姜贵庆, 艾邦成, 俞继军. 疏导热防护的固体传导的性能表征与传导特性分析[J]. 空气动力学学报, 2008, 26(1): 44-50. Jiang Guiqing, Ai Bangcheng, Yu Jijun. Analysis of solid conduction characteristics of leading thermal protection[J]. Acta Aerodynamica Sinica, 2008, 26(1): 44-50. (in Chinese)
[3] 李同起, 胡子君. 定向高导热碳材料及其热管理结构设计[J]. 航空材料工艺, 2007(1): 16-18. Li Tongqi, Hu Zijun. Carbon materials with high directional thermal conductivity and their structure design of thermal managements[J]. Aerospace Materials and Technology, 2007(1): 16-18. (in Chinese)
[4] 赵建国, 李克智, 李贺军, 等. 碳/碳复合材料导热性能研究[J]. 航空学报, 2005, 26(4): 501-504. Zhao Jianguo, Li Kezhi, Li Hejun, et al. Research on the thermal conductivity of C/C composites[J]. Acta Aeronautica et Astronautica Sinica, 2005, 26(4): 501-504. (in Chinese)
[5] Klett J, Hardy R, Romine E, et al. High-thermal-conductivity, mesophase-pitch-derived carbon foams: effect of precursor on structure and properties[J]. Carbon, 2000, 38(7): 953-973.
[6] Adams P M, Katzman H A, Rellich G S, et al. Characterization of high thermal conductivity carbon fibers and a self-reinforced graphite panel[J]. Carbon, 1998, 36(3): 233-245.
[7] Pop E, Mann D, Wang Q, et al. Thermal conductance of an individual single-wall carbon nanotube above room temperature[J]. Nano Letters, 2006, 20(6): 96-100.
[8] Hone J, Whitney M, Piskoti C, et al. Thermal conducti-vity of single-wall carbon nanotube[J]. Physical Review: B, 1999, 5(4): 2514-2516.
[9] Kim P, Shi L, Majumdar A, et al. Thermal transport measurements of individual multiwalled nanotubes[J]. Physical Review Letters, 2001, 87(21), 5502-5505.
[10] Balandin A A, Ghosh S, Bao W, et al. Superior thermal conductivity of single-layer graphene[J]. Nano Letters, 2008, 8(3): 902-907.
[11] Berger S, Kwon Y K, Tománek D. Unusually high thermal conductivity of carbon nanotubes[J]. Physical Review Letters, 2000, 84(20): 4613-4616.
[12] Osman M A, Srivastava D. Temperature dependence of the thermal conductivity of single-wall carbon nanotubes[J]. Nanotechnology, 2001, 12(1): 21-24.
[13] 刘伟强, 陈启智. 液体火箭发动机碳/碳复合材料喷管烧蚀分析[J]. 国防科学技术大学学报, 1998, 20(4): 2-4. Liu Weiqiang, Chen Qizhi. Recession analysis of carbon-carbon composite nozzle of liquid propellant rocket engine[J]. Journal of National University of Defense Technology, 1998, 20(4): 2-4. (in Chinese)
[14] 帅永, 董士奎, 谈和平. 数值模拟喷焰2.7微米红外辐射特性[J]. 航空学报, 2005, 26(4): 402-405. Shuai Yong, Dong Shikui, Tan Heping, Numerical simulation for infrared radiation characteristics of exhaust plume at 2.7μm[J]. Acta Aeronautica et Astronautica Sinica, 2005, 26(4): 402-405. (in Chinese)
[15] 陶文铨. 数值传热学[M]. 2版. 西安: 西安交通大学出版社, 2001: 176-182. Tao Wenquan. Numerical heat transfer[J]. 2nd ed. Xi'an: Xi'an Jiaotong University Press, 2001: 176-182. (in Chinese)
[16] 林群. 科学计算中的高性能有限元方法[J]. 航空学报, 2002, 23(5): 416-420. Lin Qun. Performance finite element methods in scientific computing[J]. Acta Aeronautica et Astronautica Sinica, 2002, 23(5): 416-420. (in Chinese)
[17] 李维特, 黄保海, 毕仲波. 热应力理论分析与应用[M]. 北京: 中国电力出版社, 2004: 8-17. Li Weite, Huang Baohai, Bi Zhongbo. Analysis and application of heat stress[M]. Beijing: Chinese Electric Press, 2004: 8-17. (in Chinese)
CJA