Experiment And Simulation Analysis On Thermal Deformation Of 30cm Diameter Ion Thruster

The LIPS-300 ion thruster is a kind of electric bombardment type thruster with high power and thrust independently developed in China.Its beam extraction device is a three-grid assembly with a diameter of 30 cm.The practical application shows that the gird assembly can meet the performance requirements of the thruster,but in the working state,the thermal deformation of the spherical grid will reduce the grid gap,which will lead to the performance degradation of the ion thruster,and the grid contact short circuit,which will directly cause the thruster failure.Therefore,it is of great significance to carry out research on grid thermal deformation of ion thruster,predict grid thermal deformation,fully understand the rules and characteristics of grid thermal deformation and master its mechanism to solve the problem of performance degradation or failure of ion thruster,and comprehensively improve the working performance and service life of ion thruster.Therefore,in this paper,the grid assembly of the LIPS-300 ion thruster is taken as the research object.Aiming at the thermal deformation of the grid,a series of studies are carried out through experimental measurement,simulation and theoretical calculation.The main work and innovations are as follows:1.Based on the grid thermal deformation measurement system independently developed by the research group,in the atmospheric environment,in addition to the measurement of the surface temperature field and the axial thermal deformation of the grid center,this paper also carried out the measurement of the axial rigid body displacement and the radial thermal deformation of the grid edge for the first time.The measurement accuracy of the axial thermal deformation of the grid center is further improved by obtaining the axial rigid body displacement.The radial thermal deformation of the grid edge provides an important basis for the analysis of the thermal deformation characteristics and related mechanism of the grid.2.According to the real structure of the grid assembly,a 1 / 6 rotational symmetric finite element model of the double grid module is established.At the same time,the metal drawing experiment is designed to obtain more accurate material parameters of the gate assembly.Based on the finite element model,the thermal deformation simulation of grid is carried out.Combined with the simulation results and experimental measurement results,on the one hand,the rationality and accuracy of the finite element simulation model are verified,on the other hand,the thermal deformation phenomena and rules observed in the thermal deformation experiment of grid electrode are analyzed and explained reasonably.3.Considering that the grid is a spherical thin shell structure,in order to facilitate the engineering analysis,based on the principle of material equivalence,this paper establishes the equivalent theoretical model of the thermal deformation analysis of the spherical grid,and carries out the theoretical calculation of the thermal deformation of the spherical grid by equivalent the porous shallow spherical shell structure to the non porous shallow spherical shell structure,combined with the thermal stress and thermal deformation theory of the rotating shell.By comparing with the results of experiment and simulation analysis,the rationality of equivalent theoretical model is verified,which can be used in engineering evaluation.On the other hand,it is found that the thermal deformation law and characteristics of the grid obtained by theoretical calculation are consistent with the conclusions obtained by simulation analysis.At the same time,it is found that the results of the theoretical model can further verify and support the mechanism analysis of the thermal deformation of the grid in the simulation study.