尖化前缘的稀薄气体化学非平衡流动和气动加热相似律研究

Similarity Law of Aero-Heating to Sharpened Noses in Rarefied Chemical Nonequilibrium Flows

以近空间尖前缘高超声速巡航飞行器的研制为背景,作者在前一阶段采用模型理论分析方法,陆续研究了沿微钝前缘驻点线的化学非平衡流动和气动加热相似律,文章是上述研究的综合回顾和深化讨论.稀薄条件下,驻点附近流动和传热出现一系列与连续流动模型不同的新特征,超出了经典气动热预测理论的适用范围.作者建立了一个沿驻点线能量传递和转化的广义模型,并分别推导了具有实际物理意义的边界层外离解非平衡流动判据和边界层内复合非平衡流动判据.基于这些判据构建了预测非平衡流动驻点气动加热的桥函数,并讨论了稀薄非平衡真实气体流动和气动加热的相似律,发现新型近空间尖前缘飞行器遭遇的气动热环境不同于传统大钝头航天器再入问题,传统的天地换算相似准则将会失效.这些理论分析结果可为稀薄非平衡化学反应流及气动加热的实验和计算提供一个标模检验的手段.

With a research background on the near-space hypersonic cruise vehicles, this paper is a comprehensive review and in-depth discussion of recent successive theoretical modeling studies of the similarity law of the chemical nonequilibrium flow along a stagnation streamline towards a slightly blunted nose and the related aero-heating performance. Under rarefied condition, series of new flow and heat transfer features emerge near the stagnation point, which are different from those of the continuous flow model and beyond the application scope of the classical aero-heating prediction theories. A general mod- el of the energy transfer and conversion along the stagnation streamline was proposed here, and two flow criteria with specif- ic physical meanings were introduced to characterize the nonequilibrium flows outside and inside the stagnation point bound- ary layer, respectively. Based on the criteria, a bridging function was established to predict the nonequilibrium aero-heating performance at the stagnation point, and then the rarefied nonequilibrium real gas flow and aero-heating similarity law were discussed. It turns out that the nonequilibrium aero-heating performance of the new generation near-space vehicles with sharpened leading edges is different from that encountered in the re-entry process of traditional blunt vehicles, and the tra- ditional ground-to-flight extrapolation methodology will become invalid. These analytical results provided a reliable bench- mark for experiments and numerical simulations of the rarefied nonequilibrium reacting flow and aero-heating problems.