矢量喷管内燃气辐射与壁面温度的耦合计算

选取内、外调节片和隔热屏建立几何模型,基于封闭腔净辐射模型和壁面热平衡模型建立了燃气辐射与喷管壁面温度的耦合算法.波段为1~5μm的气体辐射采用窄波带模型计算,其他波段不考虑气体辐射,建立辐射净热流密度-有效辐射亮度-壁面温度的关联式求解燃气与壁面的辐射换热,采用牛顿-拉斐尔森迭代法求解壁面热平衡方程计算其温度.对某轴对称矢量喷管(偏转20°),计算了喷管壁面的红外光谱辐射和辐射净热流密度,以及各部分结构的温度.作为验证,还计算了文献中某液体火箭发动机轴对称矢量喷管壁面的辐射净热流密度,与文献的结果进行对比一致性较好.研究表明:轴对称矢量喷管偏转段沿周向的辐射热流密度和温度差异很大,沿偏转方向部位壁面的温度和辐射热流密度都较低,偏转方向壁面的温度比相反方向大约低10%,辐射热流密度大约低50%. 

Coupled simulation of gas radiation and wall temperature in vectored nozzle

Models of heat shield and inner, outer shells were built for investigation.A coupled simulation method of gas radiation and nozzle wall temperature was established based on neat radiation in an enclosure model and heat balance model of wall.Gas radiation in 1~5μm was computed with narrow band model, which was considered transparent in all other bands.A coupled equation of neat radiative heat flux-effective radiosity-wall temperature was developed, and the Newton Rafael method was used to solve the heat balance equation to obtain wall temperature of nozzle.An axisymmetric vectored nozzle with 20°deflection angle was taken for investigation.The infrared spectral radiation and neat radiative heat flux on the nozzle wall and the wall temperature were computed.For verification of the computation method, the neat radiative heat flux for one axisymmetric nozzle of a liquid rocket motor were computed, showing well agreement through comparison. This study also shows that radiative heat flux and temperature in deflected section of axisymmetric vectored nozzle varies remarkably along the circumferential direction, much lower on the deflecting side than the other side.Wall temperature of deflecting side is about 90% of the other side, while the radiative heat flux is only 50%.