Thermal Response Analysis And Design Of Thermal Protection Structure Gap

The thermal protection systems (TPS) require gaps between the protectionelements to account for thermal expansion and deformation. However, the gapsmay induce hot gas flow into the internal TPS, leading local excessive heating.Considering fluid, thermal and structural, this paper mainly studied the thermalanalysis and design of the gap in TPS.Firstly, the gap flow characteristics especially aerodynamic heat was analyzed,by establishing the hypersonic gap flow model. The results show that the externalflow has a greater impact on the top of the gap. The upwind wall peak flux of gapis2.5times of the local flat plate. The affection of angle of attack, Mach numberand gap geometry parameters on heat flux distribution in the gap was analyzed.The study highlights that as angle of attack increasing, the influence depth on thegap aerodynamic heat rises but the influence degree reduces; Mach number has noeffect on the relative heat flux distribution in the gap; widening the gap enlargesthe influence both depth and extent of the external flow field on the gap thermalenvironment. Therefore, the gap width is the key factor to influence the internalthermal environment gap.Thermal response of the gap structure was analyzed based on the gap fluxdistribution. The results outline that the local excessive heating makes thetemperature rise rapidly, especially on the top of gap, and increases heat shorteffect caused by gap radiation. In the combined effects of the hot gas convectionand cavity radiation in the gap, widening gap increases local heat, and reaches themaximum when the gap width is4mm.The insulating tile structure pieces with different width gap were prepared,and the hot gas transient convective experiment was carried out by usingoxygen-propane gas heating platform. Experiment results indicate that when thetop gap reaches radiation equilibrium, the local heat in the middle and lower of thegap rise significantly as the width increases, which are in good agreement with thenumerical model results.Thermal-mechanical coupling analysis and optimization design was carriedout for3D insulating tile thermal protection components. Considering the localheat effect caused by the gap, the thermal-mechanical coupling analysis of thethermal protection components was accomplished under a typical reentry condition.The thermal-mechanical coupling optimization model was established, by writingan Abaqus script file and using Isight optimization platform. Considering thetemperature, stress, deformation, expansion and other aspects of the design constraints, taking the lightest weight as the goal, optimized the design parametersof insulation tile. After optimization, the quality and thickness of the structuredecreased by more than50%. Compared with the optimization results of ignoringthe local heat effect, the local heat increased the thermal protection structureoverall thickness and quality, but narrowed gap width.