共查询到18条相似文献,搜索用时 187 毫秒
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建立飞行器的热走廊物理模型和求解方法对于设计飞行器防热结构、确定飞行轨道和优化气动外形等均有重要的工程应用价值,本文对X43高超声速飞行器的飞行热走廊的物理含义进行了分析,初步建立了飞行热走廊的物理模型,给出了该物理模型下飞行热走廊的控制方程和求解方法,通过对X43高超声速飞行器典型位置的飞行热走廊的计算,研究了高超声速飞行器的热走廊规律和特征,研究了防热材料的性能对飞行走廊的限制,明确了防热材料的关键防热参数,通过研究发现: (1)防热材料的发射系数越大,其对应的热走廊越宽阔,飞行轨道的选择余地也越大; (2)不同位置、不同流态对应的热走廊边界不同,推迟转捩发生可以增加热走廊区域,有利于防热. 相似文献
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本文提出采用非均匀防热材料进行高超声速飞行器防热设计的设想,设计出外层部分为抗烧蚀、抗剪切的紧密结构材料,内层为密度轻、隔热效率高的稀松材料,中间为逐渐过渡层的非均匀防热材料,数值模拟了非均匀防热材料的烧蚀防热情况,探讨了非均匀防热材料在飞行器防热设计中应用的可行性和防热效果,通过本文研究发现采用非均匀防热材料可以降低原始材料质量消耗,大大减轻防热结构重量,减少向内部结构传导的热量,降低内部结构的温升,这些优点显示了非均匀防热材料具有很高的防热效率和广阔的应用前景. 相似文献
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针对飞行器高超声速飞行时严重的气动加热环境, 提出内嵌定向高导热层的疏导式热防护系统. 运用数值方法分析了特定条件下内嵌定向高导热层的疏导式系统的防热效果, 外壁面最高温度下降了9.1%, 内壁面最高温度下降了31.5%, 高温区和低温区都被封闭在外层区域, 内层温度更加均匀, 实现了热流由高温区向低温区的转移, 削弱了高温区的热载荷, 强化了整体结构的热防护能力. 研究表明, 随着气动热流密度比与辐射散热面积比的增大, 疏导结构的冷却效果增强. 本文还对疏导防热系统的结构参数和材料参数对冷却效果的影响进行了分析, 为结构的设计和材料的选取提供一定的依据. 相似文献
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为了研究复杂构型前缘一体化高温热管结构在高热流密度状态下的防热效果, 设计了飞行器气动加热轨道, 实现了高温热管低状态完全启动、高状态极限考核。然后采用超声速电弧风洞驻点自由射流结合轨道模拟技术, 模拟乘波体飞行器的前缘疏导构件的气动加热环境, 开展了前缘一体化高温热管结构防热效果研究。实验结果表明, 一体化高温热管结构能够多次使用, 低状态下高温热管的启动时间约为115 s, 在高状态下结构依然有效, 降温系数达到24.5%, 验证了前缘疏导式防热结构的防热效果, 可为未来新型高超声速飞行器非烧蚀热防护系统的设计提供指导。 相似文献
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低温炭化烧蚀材料的导热系数随材料的结构、工艺及使用中加热速率的不同而变化。我们采用非稳态的测试方法,利用等离子体射流加热试件,造成近于真实的烧蚀环境,得到比较真实的导热系数。 测试原理 烧蚀后的低温炭化防热材料一般分为炭化区、热解区和原始材料区。经过简化假定,可以列出描述这三个区域物理模型的微分方程。原始材料的导热系数直接影响防热层的温度分布,但若利用三个区的整套方程通过多次计算来摸清它的准确影响,不但计算量过大,而且也无法排除许多其它因素的影响。因而我们按下述原理拟定试验 相似文献
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N.Y. Bykov N.M. Bulgakova A.V. Bulgakov G.A. Loukianov 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1097-1100
We propose a hybrid model describing the processes of heating and ablation of a metal target with expansion of vaporized material into a vacuum under the action of nanosecond laser pulses of moderate intensity. The model is based on the integration of the thermal problem of laser-induced material heating and the direct Monte Carlo simulation method to describe the hydrodynamics of the ablation products. Modeling has been performed for niobium as an example and the results obtained are in good agreement with experimental data on mass removal and time-of-flight (TOF) measurements. Application of the commonly used fitting procedures for characterization of the laser plume parameters by the TOF signal is discussed. PACS 52.38.Mf; 79.20.Ds 相似文献
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系统地梳理了激光间接驱动点火靶内爆压缩的物理过程,使用理论方法和一维流体力学模拟给出了靶丸内爆过程中的关键定标律公式。通过这些定标律公式获得了在给定黑腔辐射温度、飞行熵增因子、整形速度和烧蚀材料的条件下,靶丸装量——半径参数空间的点火岛区域。研究了靶丸性能参数随辐射温度、飞行熵增因子等的变化规律:当靶丸所处黑腔辐射温度升高时,内爆的稳定性将变好;设计上在靶丸装量不变的条件下,靶丸半径需要减小。当靶丸的飞行熵增因子增大时,内爆增益略微减小,内爆稳定性变好;但是点火阈值因子减小导致点火岛的区域变窄。当靶丸的整形速度增大时,点火岛的区域略微变大,内爆稳定性变化不显著;设计上在靶丸装量不变的条件下,需要增大靶丸半径,这会导致靶丸壳层形状因子变大。当改变靶丸烧蚀材料,提高质量烧蚀速率与烧蚀压时,能量增益变大且稳定性增强;设计上在靶丸装量不变的条件下,需要减小靶丸半径。 相似文献
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Measurements of the gas-to-wall forced-convection heat transfer coefficient in a packed-bed, high-temperature, thermal energy storage system were carried out. The maximum temperature attained was 1,000°C. Effects of media property variations with temperature were incorporated along with detailed uncertainty analysis. Results were correlated in terms of Nusselt number, Prandtl number, and Reynolds number. The operating fluid during energy storage was flue gas and air during recovery, making this more applicable to industrial waste recovery and similar systems. Similar studies used air for both storage and recovery and developed correlations from experiments at either room temperature or slightly above. Few associated results with corresponding uncertainty margins. Due to substantial uncertainties associated with the measurements of this heat transfer coefficient, it is significant to note that no firm conclusions can be reached on the validity or otherwise of existing similar correlations for which the uncertainty margins were not reported. 相似文献
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S. Gryś 《Opto-Electronics Review》2011,19(2):234-241
A new kind of thermal contrast, called “filtered contrast” is presented, which allows detecting and characterizing material
defects using active thermography under some assumptions on physical and thermal parameters of materials. In opposition to
known definitions of the thermal contrast, knowledge about defect-free area is not necessary and this contrast is less sensitive
to nonuniformity of heat disposal to the material surface. The measurements were performed on an experimental setup equipped
with a ThermaCAM PM 595 infrared camera and frame grabber. The step heating was chosen as heat excitation. The results demonstrate
usefulness of the 1D model of heat transfer used for determination of depth of subsurface defects. The influence of the parameter
of the smoothing filter, required for filtered contrast implementation, thermal parameters of the tested material and defect
on expanded uncertainty of determination of defect depth is also presented. Due to significant complexity of the model of
heat transfer, the conditions for the “law of propagation of uncertainty” were not fulfilled and a numerical method, i.e.,
Monte Carlo simulation is applied for the propagation of distributions. 相似文献
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针对电源电路抗总剂量辐射性能评估问题,建立了元器件和电路的性能模型,并搭建测试电路对模型进行了测试。开展了辐照敏感关键元器件的总剂量辐照试验,获取了元器件关键参数随累积总剂量变化的实验数据,将参数变化规律注入模型,开展了电源电路抗辐射性能仿真,获得了电路关键特征参数输出电压随累积总剂量的变化规律。采用裕量与不确定性量化(QMU)方法对电源电路的抗辐射性能进行评估,并与电路实际辐照实验结果进行对比,结果表明,QMU评估结果与实际实验结果保持了较好的一致性。 相似文献
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为了分析飞秒激光烧蚀过程,在双相延迟模型的基础上建立了双曲型热传导模型.模型中考虑了靶材的加热、蒸发和相爆炸,还考虑了等离子体羽流的形成和膨胀及其与入射激光的相互作用,以及光学和热物性参数随温度的变化.研究结果表明:等离子体屏蔽对飞秒激光烧蚀过程有重要的影响,特别是在激光能量密度较高时;两个延迟时间的比值对飞秒激光烧蚀过程中靶材的温度特性和烧蚀深度有较大的影响;飞秒激光烧蚀机制主要以相爆炸为主.飞秒激光烧蚀的热影响区域较小,而且热影响区域的大小受激光能量密度的影响较小.计算结果与文献中实验结果的对比表明基于双相延迟模型的飞秒激光烧蚀模型能有效对飞秒激光烧蚀过程进行模拟. 相似文献