潜入式喷管喉衬界面间隙优化设计

为了解决固体火箭发动机潜入式喷管喉衬在热载荷与内压联合作用下界面间隙优化问题，数值模拟方法求解了喷管热结构响应。采用流体仿真软件，计算了潜入式喷管流动过程的稳态流场，获取了高温燃气流动参数与固体壁面对流换热系数。并采用三维有限元结构计算平台，编写了非均布壁面压力载荷与非均布对流换热系数子程序，求解了喉衬前后搭接界面间隙在0mm，0.05mm，0.10mm，0.15mm，0.20mm下喷管热结构耦合问题，获取了材料内部温度场与应力场分布。结果表明，喉衬环向压应力与拉应力都随时间增加，先增大后减小。其次，随间隙增大，喉衬拉应力先减小后增大，喉衬压应力先增大后减小。再次，依据界面闭合与喉衬环向受力最小的准则，确定了喉衬前后间隙的相对最优值，前间隙相对最优值0.10mm，后间隙相对最优值0.05mm。本文数值方法可为喷管热防护材料界面搭接与喉衬界面间隙设计提供指导，也可应用于评估喷管热防护与结构强度安全余量。

Research on Optimal Design for Interfacial Gap for Submerged Nozzle Throat Insert

By means of three-dimensional finite element method with the subroutine of non-uniform pressure and non-uniform convective heat transfer coefficients, which were obtained by flow simulation software, thermo-structural phenomenon has been discussed for submerged nozzle of solid rocket motor upon thermal loading and aerodynamic pressure, when the value of interfacial gap for throat insert is 0mm, 0.05mm, 0.10mm, 0.15mm, 0.20mm, respectively. The field of temperature and stress has been determined. The research shows that the hoop compressive stress and tensile stress of throat insert increase with time. Secondly, with the increase of interfacial gap, the tensile stress of throat insert decreases at first and then increases, and the compressive stress of this first increases and then decreases. Thirdly, according to the criterion of interface closure and the minimum hoop stress, the optimal value of interfacial gap for throat insert is obtained. Finally, the analyses of gap design and join interface can be conducted by the present numerical method. The margin about thermal protection and structural strength of the nozzle can be determined, too.