30cm离子推力器栅极组件热应力及热形变计算模拟

Thermal Stress and Thermal Deformation Analysis of Grids Assembly for 30cm Diameter Ion Thruster

关键词:  离子推力器  栅极组件  热应力  热形变

Key words:  Ion thruster  Grids assembly  Thermal stress  Thermal deformation

摘要:

为了降低30cm口径离子推力器栅极组件工作时的热形变位移，采用材料力学分析以及有限元分析方法研究了边缘不约束和边缘约束下的栅极组件热应力分布以及热形变位移，提出了相关的热应力降低措施并进行了模拟验证。结果显示，将栅极等效为圆形平板且边缘无约束时，水平方向的拉伸应力引起的最大热形变位移约为0.3mm，栅极几何中心处的热应力最大，约为1.5MPa，法线方向的热形变位移基本为0；将栅极等效为圆形平板且边缘约束时，最大挠度出现在结构几何中心处，约为1.255mm，水平方向最大拉伸形变量为0.01mm，理论计算值与仿真结果基本一致，且真实栅极拱形结构在此约束条件下会产生更大的热形变位移，可能导致栅极的聚焦性能变差以及栅极之间的短路现象；热设计改进措施验证表明降低结构的整体温度并且更换热膨胀系数较低的材料是减小热形变位移的较好措施。

Abstract:

In order to decrease the thermal deformation displacement of the 30cm diameter ion thruster’s grid components，material mechanics analysis method and finite element method were used to study distribution of thermal stress and thermal deformation displacement of grid components with and without edge constraint condition，related optimization measure and validation process are proposed. The obtained results indicate that，when the grids are equivalent to circular plates and the edge constraints do not exist，the maximum thermal deformation of the grid caused by tensile stress is about 0.3mm，and the maximum thermal stress is about 1.5MPa which occurs in the center of grids，while the deformation displacement in the normal direction is nearly zero. When the grid is equivalent to the circular plate and the edge constraint condition satisfies，the maximum deflection occurs at the geometric structural center，with its value being about 1.255mm，and the maximum tensile deformation in the oriental direction being 0.01 mm. The theoretical results are in rough agreement with the simulation results，and the real grid structure will cause larger thermal deformation displacement under this constraint condition，probably causing the grid’s bad focusing performance and short between the grids.The thermal design optimization validation indicates that decreasing the overall temperature distribution of the structure and using the material with small thermal expansion coefficient are good measures to reduce the thermal deformation.