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基于DSMC方法的再入飞行器微烧蚀研究

DSMC STUDY OF MICRO-ABLATION FOR REENTRY VEHICLES

  • 摘要: 高超声速再入飞行器面临着严峻的气动热环境, 准确预测微烧蚀过程对热防护系统的设计至关重要. 由于烧蚀会改变气动外形, 进而影响周围的气动热环境以及烧蚀过程本身, 因此需要将烧蚀过程与流场变化进行耦合计算. 文章采用基于直接模拟蒙特卡洛(DSMC)方法的开源程序SPARTA, 对高超声速条件下的再入飞行器表面微烧蚀问题展开研究. 为构建并测试通用的耦合算法, 通过典型的一维烧蚀模型改进了SPARTA的动能烧蚀模型并采用烧蚀表面热平衡模型计算烧蚀速率, 结合Marching Square算法的特点修改了网格节点的计算方法. 针对柱体、球锥以及带有微小粗糙元的斜楔体等典型外形, 文中计算了二维条件下不同气动外形的烧蚀过程并进行了详细分析. 其中球锥截面烧蚀预测结果中沿驻点线的烧蚀面呈现出较快的衰退速率, 并且与文献中驻点附近的结果吻合情况较好. 斜楔体的烧蚀结果表明, 微小粗糙元的附近存在着非常稀薄的流场区域, 并且其与头部驻点区域会率先发生烧蚀, 反映了再入飞行器表面的微烧蚀特征. 烧蚀结果对高超声速下微烧蚀机理的研究以及热防护系统的设计具有参考意义.

     

    Abstract: Hypersonic reentry vehicles are subjected to a severe aerodynamic thermal environment during a high-speed flight. Accurate prediction of micro-ablation process is quite crucial for the design of thermal protection systems (TPS). Since the aerodynamic shape changes due to the ablation process, which in turn will affect the aerodynamic thermal environment around the aircraft and then the ablation process itself, coupled calculation between the ablation and the flow field is required. This study uses the open source DSMC kernel SPARTA to study the micro-ablation phenomena under extreme conditions for the surfaces of hypersonic reentry vehicles. In order to construct and test a general coupling algorithm, significant improvements have been made to the program. The kinetic ablation model in SPARTA is improved based on the one-dimensional ablation model. Besides, the computing method of the ablation rate has been adapted to be more accurate after employing the ablation surface thermal equilibrium model, and the grid corner values are modified combined with the basic characteristics of Marching Square algorithm and the ablation rate. In this paper, the ablation processes of typical aerodynamic shapes such as cylinders, a blunt cone, and a wedge with a small obstacle are simulated and analyzed under two-dimensional conditions. The predicted surface of cone section along the stagnation streamline shows a faster recession rate, which achieves a good agreement with the result in the literature. In addition, the ablation results of the wedge indicate the existence of an extremely rarefied flow region near the obstacle, which undergoes a distinct shape change rapidly along with the head stagnation point after the ablation process happens. These findings have illuminated the characteristics of the micro-ablation process for the hypersonic reentry vehicles, offering valuable guidance for the design of thermal protection systems and advancing our understanding of the ablation mechanisms pertinent to the hypersonic flight vehicles.

     

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