Numerical Simulation Study On Thermal Deformation Of Thin-walled Spherical Molybdenum Grids Assembly With Weak Stiffness

The grids assembly is the key component of the ion thruster.At present,the structure design of grids assembly can meet the performance requirements of the thruster,but due to thermal deformation and other factors,there are still some shortcomings in long life and high reliability stability,affecting the performance and stability of the thruster.Therefore,it is of great practical significance for improving the reliability of the thruster and promoting the engineering of the thruster to carry out relevant research on the structure characteristics and working environment of the grids assembly,explore effective methods for predicting the thermal deformation of the grid assembly,and analyze the laws and influencing factors of the thermal deformation of the grids assembly.Therefore,based on the actual background of the thermal deformation of the structure caused by the uneven temperature field when the grid is working,this paper designs the artificial heating experiment of the grid module under the atmospheric condition,and carries out a series of research combined with the modeling and thermal deformation simulation technology of the grid module.The main tasks are as follows:(1)The artificial heating experiment of grids assembly under atmospheric conditions was carried out,and the temperature field and thermal deformation of grid structure were simulated and analyzed.In this paper,the artificial heating experiment of grids assembly under atmospheric conditions is designed.The real-time data of temperature field,thermal deformation at center point and center distance of grids assembly are measured and analyzed.At the same time,the characteristics of grid structure are studied.A full-size shell element model is established.The boundary conditions of the model are set according to the experimental conditions.The temperature field and thermal deformation of the grid are simulated and analyzed,and the accuracy of the finite element model and method is verified by comparing the experimental and simulation results.(2)The calculation accuracy and efficiency of grid models with different element types are compared and analyzed,and the influencing factors of grid thermal deformation are analyzed.According to the characteristics of grid structure,the full-size solid element and beam element models are further established,and the calculation efficiency and accuracy of grid models with different element types are compared and analyzed.On this basis,the influence factors of grid thermal deformation are analyzed.(3)An equivalent model which is basically consistent with the results of the thermal deformation calculation of the full-size model of the grid is established.Based on the principle of material equivalence,the equivalent material parameters of the grid are obtained by finite element method.The grid is further equivalent to a flat spherical shell without holes.The results are compared with those of the full-size model.The results show that the calculation results of grid equivalent model is basically consistent with those using full-size model.On the other hand,the thermal stress and deformation theory of the revolution shell are used to solve the thermal deformation of the grid equivalent model,and a simpler method is obtained.