Study Of Thermo-Mechanical Coupled Computation For Thermal Protection System Of Reusable Launch Vehicle

Design and analysis of thermal protection systems (TPS) is one of key technologies of reusable launch vehicle (RLV). Exploring to numerical calculation method of TPS design and analysis, determining the effect of structural parameters on temperature and mass distribution of RLV, thermo-mechanical coupled problem that is produced by thermal shock when RLV fly back to earth, and such problems are all major research subjects in design and analysis of TPS.Based on Galerkin numerical theory, this dissertation studies in details numerical calculation methods of linear and nonlinear transient heat transfer equation, the major contents of which include: deducing isoparametric finite element formulations of orthotropic materials; giving detailed coordinate transforming relationships between material coordinate, normalized parametric coordinate and structural global coordinate systems; interpolating piecewisely quadratic function for temperature through layers of composites shell, considering that thermal load performs thermal shock; and proposing different element expressions of temperature functions and finite element formulations under different specified boundary conditions; getting a whole set of numerical calculation method of thermal shell element to analyze orthotropic materials. On the basis of these works, with breaking through tradition method, a degenerated 3D shell element with 8 nodes and high numerical precision is created and finite formulations are obtained. Such the shell element reduces half of the thermal analysis variables and is proved to be correct and high efficient by numerical examples. According to relative degree-of-freedom (DOF) theory, this dissertation also studies relative DOF thermal shell element, and compares the advantages of this element with others by numerical examples. The results prove the formulations of relative DOF element are effective in the context of dealing with internal thermal boundaries.For typical metallic honeycomb kind of TPS, this dissertation constructs the numerical model of honeycomb core, builds numerical formulations of 2D thin plate in 3D space, and deduces 4 nodes finite element formulations. On the basis of these analyses, this dissertation discusses numerical model of honeycomb and boundary conditions, and determines the sizes, boundary conditions and the heat flux load for the model. Due to the complexity of honeycomb materials, this dissertation refers to some formulations for calculating materials built-up properties in reference of technology information of other documents. Through a lot of computational efforts, the effect of structure size and different radiation on temperature distribution is studied, and also the sensitivity of structural parameters to temperature is obtained.