火箭发动机羽流辐射与底部结构温度的耦合理论与实验研究

The coupled study of plume radiation and the three dimensional temperature at base of the rocket engine is very important for prediction of thermal environment of rocket base structure, which will also improve the precisely heat protection design of rocket base, and would promote the development of re-useable launch vehicles. The present researches have many restrictions in application. One marked restriction is the model of spectral properties for gases and particles in the plume, which is not easily to be implemented efficiently and exactly. Another marked restriction is the model for three dimensional temperature of the base structure, which tend to be too rough without coupled simulation with the spectral model for radiative flux. To improve the precision and flexibility of numerical model for plume radiation and structure temperature analysis, and to overcome above restriction, the coupled study of the plume spectral radiation field and the three dimensional temperature for the rocket engine is to be carried out in this proposal, based upon the prepared study of the applicant. The full spectrum correlated coefficient model will be forwarded to compute the spectral properties of plume gases, and the Mie scattering model will be developed to compute the spectral properties of liquid and solid particles with high temperature. The discrete ordinate method will be applied to solve the three dimensional, global and full spectrum radiation field of the plume. A moving boundary model will be established for simulation of the ablation process on the nozzle wall. The Q-J-T equation for the radiative transfer flux is to be coupling solved with the three dimension heat conduction equation to give the detailed structural temperature. As the effective test and supplementing study of the theoretical analysis, the grounded numerical experiment with sub-scaled modeled rocket will be implemented, radiation intensity of the plume and the structural temperature will be measured, and the similarity analysis of plume radiation will be taken to correct the theoretical model. The ultimate goal of the whole study in this proposal is to provide the fundamental and reliable basis for the precisely design for heat protection of the rocket base.

研究火箭发动机羽流辐射及耦合的发动机底部结构三维温度场，对于预测火箭底部结构的工作热环境，增强火箭发动机底部结构的精确热防护设计，发展运载火箭的可重复使用设计有重要意义。目前用于高温气体和粒子光谱特性的模型难以快速精确地计算火箭发动机羽流的光谱参数；且计算结构三维温度场的模型，由于未与辐射换热的光谱分析模型耦合而精度较低。本申请拟在前期研究的基础上，开展火箭发动机羽流光谱辐射场与结构温度场的耦合研究：构建全光谱关联吸收系数模型和Mie 散射理论，分别计算羽流气体和高温液、固态粒子的光谱特性；采用离散坐标法（DOM）求解羽流的三维全向全光谱辐射场；构建移动边界模型进行喷管壁面烧蚀过程的分析；将计算辐射热流的Q-J-T 方程与结构三维热传导方程耦合求解温度场；最后借助地面缩比模型数值实验，获得羽流辐射强度和发动机底部结构的温度，结合相似分析，校正理论模型，为火箭底部结构的精确热防护设计提供依据。

围绕火箭发动机羽流辐射场计算、羽流对火箭底部的辐射加热机理，及羽流辐射作用下火箭底部的三维温度特性，展开研究，取得大量有益的成果。研究项目预定的目标是在国内外重要期刊或高水平国际会议上发表学术论文9~12篇，其中在SCI检索期刊上发表论文3~5篇。目前已经发表期刊论文23篇，其中SCI检索6篇，EI检索10篇，在IEEE Aerospace Conference会议发表论文2篇，达到并超过项目计划书设定的目标。.研究了不同缩比尺寸的固体火箭发动机羽流辐射的相似特征，获得三叉戟D5火箭发动机在地面工况下，缩比模型的羽流辐射与原尺寸发动机羽流辐射间相似关系，对地面工况下，几何尺寸缩比为0.1、0.2、…、1的发动机，计算与发动机轴线成0、30、60和90度方向的红外光谱辐射和波带辐射。研究了固体火箭发动机在地面工作过程中喷管的受热与烧蚀，对某型发动机工作后140s时间内复合喷管壁面受到管内高温喷流辐射与对流加热、以及发动机外部环境辐射与对流冷却条件下的壁面受热与材料热解烧蚀建立一维非稳态热分析模型进行计算分析。研究固体火箭发动机地面和高空飞行过程中羽流红外辐射随飞行高度的变化，计算某型固体火箭发动机在地面试车和7.5km~80km之间一系列高度工况下，发动机内、外流场和红外波段2~6μm的辐射，获得2.7~2.95μm、3.6~3.85μm和4.2~4.45μm三个波段，羽流高温核心区表面的辐射强度；以及高温核心区在轴向主平面和法平面上，0°、45°和90°三个视角的辐射亮度。还对矢量喷管的冷却及红外辐射展开研究，燃气红外波带的光谱特性采用窄波段模型计算，壁面-燃气辐射采用封闭腔模型计算，喷管收敛段的气膜冷却采用绝热温比计算。详细计算了一收敛段采用多排缝槽气膜冷却的轴对称矢量喷管，得到了扩张段偏转20°工况以及非偏转工况下的结构温度以及喷管向后半球的红外辐射，得到的研究结果对矢量推进技术发动机排气系统的冷却具有重要参考价值。