近空间飞行环境泰氟隆烧蚀流场化学非平衡流数值算法及应用研究

Application and numerical method of chemical non-equilib rium flow for Teflon ablative flow fields in near-space flying condition

本文通过数值求解考虑烧蚀产物在内的23种组分的化学非平衡Navier-Stokes方程,建立考虑泰氟隆材料烧蚀效应的化学非平衡流数值计算方法.理论预测了球锥体RAMC-II的等离子体鞘套电子数密度,并和飞行试验进行比较,验证了算法可靠性,揭示了电子数密度峰值结果在25–70 km中层近空间随飞行高度变化规律.算法应用于不同高度球锥体泰氟隆烧蚀流场计算,研究表明,在泰氟隆烧蚀现象比较明显的中低空,烧蚀产物对电子数密度的影响主要局限在边界层内;泰氟隆烧蚀导致边界层内流场温度降低,因而引起空气阴离子的增加,另一方面随着飞行高度降低,由亲电子产物引起的F?数量也不断增加,这些因素引起了边界层内的电子数密度降低.

A numerical method has been established and applied to compute the chemical non-equilibrium flow involving Teflon ablative effect, where the chemical non-equilibrium Navier-Stokes equation is solved by taking account of 23 species including the ablative products. The computational results of electron number density in the plasma sheath for the sphere-cone RAMC-II are well compared with those of flight experiments. The reliability of the present method has been validated in near-space flying condition, and the varying feature of the electron number density with flight altitude has been revealed. The present numerical method is applied to compute the Teflon ablative flow field past sphere-cone body with different altitudes of 25-70 km. It is indicated that the effect of ablative products on electron number density is mainly limited in the region of boundary layer while the phenomena of Teflon ablation are obvious at moderate and low altitudes. The decrease of temperature in the boundary layer is caused by the Teflon ablation which results in the increase of the number of negative air ions. On the other hand, the number of F- from electrophilic species of Teflon-air reactive mixtures increases continuously with the decrease of flying altitude. These factors cause the reduction of electron number density in the boundary layer.