平流层飞艇大型充气结构热流固耦合机理研究

With the advantage of long endurance, station keeping and low cost-effectiveness, stratospheric airships have the potential to be the platforms suitable for applications and missions such as earth observation, surveillance, navigation, communication relay and broadcasting. As a large-scale flexible inflatable structure by a huge inner lifting gas volume of several hundred thousand cubic meters, the stratospheric airship's inner gas characteristic plays an important role in its structural performance. During the ascent/descent and floating flight, the variations of the combined thermal condition lead to the fluctuations of the flow field inside the airship, which will remarkably affect the pressure acted on the skin and the structural distortion of the stratospheric airship. According to the multi-physics coupling mechanism mentioned above, a numerical procedure of thermal-fluid-structure interaction analysis of stratospheric airships is developed and the thermal model, CFD model, finite element code and criterion of structural strength are integrated considering various nonlinear behaviors. Based on the validation of the computation models, the distributions of the deformations and stresses of the skin are calculated with the variation of day-night time and material parameters. The effects of flight conditions and structural configurations on the structural safety of stratospheric airships in the ascent/descent and floating condition are evaluated. The numerical results can be referenced for the structural design of stratospheric airships.

平流层飞艇是工作在临近空间的新型平台，具备持久区域驻留的信息获取与信息对抗能力，有广阔的应用前景和重要价值。不同于飞机、卫星等飞行器，平流层飞艇是一种大型的充气结构，内部大量浮升气体形成内流场，内部气体状态对外部空间环境较为敏感，考虑到外部风场影响，其在上升/下降和昼夜驻留过程中会发生较复杂的热流固耦合作用，对飞行性能和结构安全性具有重要影响。本项研究以大尺度充气结构设计理论为基础，考虑薄膜结构大变形、结构褶皱屈曲、索膜接触、刚柔连接、主副气囊耦合等影响，建立平流层飞艇大型充气结构的精细化非线性有限元模型，综合考虑内外流场作用提出基于分区耦合策略的平流层飞艇充气结构热流固耦合计算方法，揭示平流层飞艇热流固耦合作用机理，深入研究不同飞行条件下软式和半硬式布局平流层飞艇结构安全性，为平流层飞艇结构设计提供理论依据和技术支撑。

平流层飞艇升降与昼夜驻空过程中，其大尺度柔性充气囊体结构在外部环境和内部气体流场的作用下会发生较复杂的热流固耦合作用，对飞行性能和结构安全性具有重要影响。本项目基于传热理论建立了囊体结构热特性计算模型、采用CFD方法建立了囊体内外流场计算模型，基于壳单元理论建立了结构有限元模型，综合提出了平流层飞艇囊体结构热流固分区耦合计算方法，针对平流层飞艇软式和半硬式两种结构形式，开展了升降和昼夜驻空条件下的结构安全性仿真计算，得到了上升过程中软式囊体结构薄膜褶皱数量和幅值特征，分析了驻空过程中囊体结构薄膜与太阳电池阵列连接处的应力集中机理，得到了下降过程中半硬式囊体结构的薄膜和骨架变形特征和变化规律。项目研究成果对于大尺度柔性充气薄膜结构设计具有重要意义。