潜入式喷管喉衬界面间隙优化设计

Optimal Design for Interfacial Gap for Submerged Nozzle Throat Insert

关键词:  固体火箭发动机  潜入式喷管  有限元方法  热应力  界面应力

Key words:  Solid rocket motor  Submerged nozzle  Finite element method  Thermal stress  Interface stress

摘要:

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。

Abstract:

In order to solve the problem of the optimization of interfacial gap for submerged nozzle insert throat of solid rocket motor upon thermal loading and aerodynamic pressure， the simulation was performed to study the thermo-structural response of a submerged nozzle. By means of fluid simulation software， the steady flow field of nozzle flow was obtained， and the flow parameters of high temperature gas and convective heat coefficients of nozzle wall were obtained. Meanwhile， based on three-dimensional finite element software with the subroutine of non-uniform pressure and non-uniform heat transfer coefficients， the thermo-structural response of the submerged nozzle was solved， when the value of interfacial gap for throat insert is 0mm， 0.05mm， 0.10mm， 0.15mm， 0.20mm， respectively. The distribution of temperature field and stress field were obtained for the submerged nozzle. The results show that both the hoop compressive stress and tensile stress of throat insert increase at first and then decrease with the increase of time. Secondly， with the increase of interfacial gap， the tensile stress of throat insert decreases at first and then increases， while the compressive stress first increases and then decreases. Thirdly， according to the criterion of interface closure and the minimum hoop stress， the relative optimal value of interfacial gap for throat insert is obtained. The relative optimal value of front gap is 0.1mm， and the relative optimal value of rear gap is 0.05mm. The analyses of gap design and join interface can be conducted by the present numerical method， and the margin about thermal protection and structural strength of the nozzle also can be determined， too.