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控制方程为三维Navier-Stokes方程,其无量纲化形式如下[6]:
$$\begin{split} & \frac{{{\text{∂}} Q}}{{{\text{∂}} t}} + \frac{{{\text{∂}} F}}{{{\text{∂}} x}} + \frac{{{\text{∂}} G}}{{{\text{∂}} y}} + \frac{{{\text{∂}} H}}{{{\text{∂}} z}} = \\ & \frac{1}{{{Re} }}\left( {\frac{{{\text{∂}} {F_V}}}{{{\text{∂}} x}} + \frac{{{\text{∂}} {G_V}}}{{{\text{∂}} y}} + \frac{{{\text{∂}} {H_V}}}{{{\text{∂}} z}}} \right) + W \end{split} $$ (1) 式中:Q为守恒变量;F、G、H为直角坐标系下个方向的对流通量;
$ {F_V}{\text{、}}\!\!\!{G_V}{\text{、}}\!\!\!{H_V}$ 为各方向的粘性通量;W为化学反应源项。采用12组分31化学反应模型,其中包含O2、N2、NO、N、O、NO+、e−、CO、CO2、CN、C、C2高温空气组分,采用LU-SGS隐式有限差分方法对方程(1)进行离散求解,其中对流项与化学反应源项采取隐式处理方法,无粘项采用AUSMPW+二阶格式离散,粘性项采用中心差分格式离散,多组分混合气体的粘性系数μ和热传导系数
$k$ 用Wilke半经验公式计算,各组分的输运系数用Blotter曲线拟合公式和Eucken关系式,扩散系数采用等效二元扩散模型,具体数值计算方法见参考文献[6]。 -
高温气体流场热辐射的控制方程为局部热力学平衡下的辐射传输方程[7-9]:
$$\frac{{{\rm{d}}{I_{\nu} }}}{{{\rm{d}}\ell }} = {k_{\nu} }({B_{\nu} } - {I_{\nu} })$$ (2) 式中:
$\ell $ 为辐射传输路径;${I_{\nu} }$ 为光谱辐射亮度;$k{}_{\nu} $ 为光谱吸收系数;${B_{\nu} }$ 就是黑体辐射强度,其表达式为:$${B_{\nu} }(T) = \frac{{2h{\nu ^3}/{c^2}}}{{{{\rm{e}}^{h\nu /kT}} - 1}}$$ (3) 式中:h为普朗克常数;v为波数;k为波尔兹曼常数;c为光速;T为温度。
通过对火箭发动机尾焰流场(CO、CO2、H2O、N2、OH、HCl、N、NO、O、O2等)和碳基材料烧蚀流场中(O2、N2、NO、N、O、NO+、CO、CO2、CN、C、C2等)化学组分辐射机制和它们在流场中浓度分布的细致分析,在红外光谱区主要考虑如下5种辐射机制:(1) NO基态(5.3 µm)和第一谐波带系(2.7 µm);(2) CO的基态(4.67 µm)和第一谐波带系(2.34 µm);(3) OH的基态(2.8 µm)和第一谐波带系(1.4 µm);(4) CO2的红外带系(15、4.3、2.7 µm);(5) H2O的红外带系(6.27、2.66、1.88 µm等);另外还考虑了O和N的连续谱辐射。
考虑到上述高温流场气体辐射机制的复杂性,在求解公式(2)时采用气体光学薄的假设,采用带辐射模型计算光谱吸收/发射系数[9],先采用Z-buffer消隐技术[10],剔除弹体对高温流场辐射的遮挡,然后计算在气体组分辐射机制下网格体微元在每个谱带内的光谱辐射强度并积分得到观测方向的高温气体流场的光谱辐射强度,最后对高温气体流场光谱辐射强度在特定探测光谱波段内积分获得该光谱波段的辐射强度。
IR radiation characteristics of India Angi-Ⅱ at launching and reentry stage
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摘要: 弹道导弹发射阶段发动机尾焰中的H2O、CO2等大量高温气体组分和弹头再入段高温气体流场以及受气动加热的本体均产生强烈的红外辐射,是红外预警、跟踪、制导的重要信号。针对印度烈火-Ⅱ导弹,开展其助推段和再入段的辐射特性计算分析。从窄带辐射模型出发,考虑流场中重要气体组分的红外辐射机制,建立高温气体组分光谱参数的计算方法,发展了目标红外辐射特性计算软件。根据助推段火箭发动机尾焰流场和再入段流场的数值模拟的物理化学参数,利用所发展的辐射计算软件,计算分析了烈火-Ⅱ导弹助推段和再入段典型状态的红外辐射特性,可以为针对烈火导弹的预警、反导提供参考。Abstract: The high temperature gas such as H2O and CO2 of the exhaust plume of a launching ballistic missile will bring strong IR radiation, so it is the aero heated warhead and the high temperature gas flow around the warhead. The IR radiation is an important signal for IR early warning, tracking and guiding of target in the near-space. The IR radiation characteristics of Angi-Ⅱmissile during launching and reentry stage was studied. Based on narrow band radiation model, and the radiation mechanism of vital gas species were taken into account. The methods for spectral parameters calculation of the species in the high temperature flow were set up, and then a computer code was developed for IR characteristics of targets in the air, which can compute IR characteristics of warhead body and high temperature flow. According to simulated data of the exhaust plume flow and reentry flow around the warhead, the radiation code was used for computing the IR characteristics of Angi-Ⅱ at launching and reentry stage, which can be used as references for early warning and anti-ballistic missile about Angi-Ⅱ.
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Key words:
- Angi-Ⅱmissile /
- rocket plume /
- launching stage /
- reentry stage /
- IR radiation
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