表面烧蚀对等离子体的影响及其与电磁场相互作用

Influence of surface ablation on plasma and its interaction with electromagnetic field

表面烧蚀显著影响高速流动中等离体子鞘分布及其与电磁场相互作用的特征.考虑高超声速飞行器表面烧蚀引射机制、烧蚀产物参与流场等离子体生成过程、含碱金属的混合电离气体导电机理和电磁动力学机制,通过耦合求解带电磁源项的三维热化学非平衡流动控制方程、电场泊松方程和磁矢量泊松方程,建立了含碱金属烧蚀的高速流动/等离子体/电磁场耦合计算方法,结合常见的碳碳材料和硅基酚醛树脂材料烧蚀热解过程,较为系统地开展了多种条件下表面烧蚀对高超等离子体鞘影响及其与电磁场相互作用的机制与规律研究.研究表明:烧蚀效应对流场等离子体分布的影响受烧蚀质量引射率和碱金属质量占比共同作用,当碱金属含量较高时,碱金属电离反应占主导,电子数密度可增大1—2个数量级;不同材料烧蚀对等离子体的影响存在差别,硅基酚醛树脂的烧蚀质量引射率较大,电离生成CO^(+),C^(+)的摩尔分数接近空气主要电离组分NO^(+),O_(2)^(+),其影响不容忽视;烧蚀材料中碱金属可以显著提升磁流体力学控制效果,随着碱金属占比增大,电磁场耦合作用效果增强,二者呈非线性关系;在速度较低时,纯空气本身的电离度低导致电磁场耦合作用效果弱,通过含碱金属烧蚀来提升电磁作用效果的效率更高.

Surface ablation significantly affects the distribution of plasma in high-speed flow and the characteristics of its interaction with electromagnetic fields.Considering the mechanism of ablation and ejection on the surface of hypersonic vehicle,the participation of ablation products in the plasma generating process in the flow field,the conduction mechanism of mixed ionized gas containing alkali metal and the electromagnetic dynamics mechanism,the coupled calculation method of high-speed flow/plasma/electromagnetic field with alkali metal ablation is established by solving the three-dimensional thermochemical non-equilibrium flow governing equation with electromagnetic source term,the electric field Poisson equation and the magnetic vector Poisson equation.Combined with the common ablation and pyrolysis process of carbon-carbon materials and silicon-based phenolic resin materials,the mechanism and law of the interaction between surface ablation and electromagnetic field on the hypersonic plasma sheath under various conditions are systematically studied.The results show that the ablation effect affects the plasma distribution in the flow field,which is affected by the ablation mass ejection rate and the mass proportion of alkali metal.When the alkali metal content is high,the alkali metal ionization reaction is dominant,and the electron number density can increase by 1-2 orders of magnitude.The influences of different materials on plasma are different.The mass ejector ratio of silicon-based phenolic resin is larger,and the molar concentration of CO+and C+produced by ionization is close to that of NO_(2)+ and,which cannot be ignored.Alkali metal in ablative material can significantly improve the control effect of magnetohydrodynamics.With the increase of the proportion of alkali metal,the coupling effect of electromagnetic field increases,and the relationship between them is nonlinear.When the speed is low,the ionization degree of air itself is low and the coupling effect of electromagnetic field is weak.But the efficiency of“improving the electromagnetic effect by ablation of alkali metal”is higher.