Numerical Simulation Of The Plasma In Kaufman-type Ion Thruster

Presently,electric thruster has become the main thrust device for on-orbit space missions.Kaufman-type ion thruster is one of the electric thrusters with the highest efficiency and specific impulse.And it is also one of the most widely used ion thruster.However,with the increase of size and power,as well as the change of structure(like the Annular ion thruster with non-axisymmetric structure),many new problems have emerged and need to be solved urgently,like the worse uniformity of plasma in discharge chamber,the lower service life of ion optics,etc.Due to the high cost and long cycle of the experimental method,numerical method has become the preferred method for the development of Kaufman-type ion thruster.The research object of this dissertation is the plasma in discharge chamber,optics and plume,in which the simulation of the plasma in discharge chamber is the core.Numerical simulation method is utilized to illustrate the plasma characteristics in Kaufman-type ion thruster more clearly,so as to assist its further development.The main research work of this paper is as follows:Firstly,for the anisotropic plasma in discharge chamber,a 3D anisotropic immersed finite element(IFE)method is developed.This IFE method can solve the plasma anisotropic diffusion problem with complex interfaces on structured meshes.It not only has good computational efficiency,accuracy and convergence,but also has good versatility,and can solve different types of interface problems,like anisotropic or isotropic homogeneous and nonhomogeneous elliptic interface problems.Secondly,based on the plasma bipolar diffusion description and the Particle-in-cell Monte Carlo collision(PIC-MCC)method,a hybrid-PIC decoupling iteration method for solving the control equations of discharge chamber is proposed.By combining the hybrid-PIC decoupling iteration method with the IFE method,a 3D model is proposed for the discharge chamber,which can be used to the simulation of non-axisymmetric discharge chamber.Due to the high efficiency of the hybrid-PIC decoupling iteration method,this model aslo has good computational efficiency.Compared with the experimental results of the traditional ion thruster(LIPS-300)and 5k W Annular ion thruster developed by the Lan Zhou Institute of Physics,it is shown that this model also maintains good accuracy and can effectively predict the performance of the discharge chamber.Thirdly,by using the proposed 3D discharge chamber model,the influence of different parameters on the plasma characteristics is studied.Furthermore,an Annular ion thruster configuration is proposed to improve the plasma uniformity.The simulation results show that: for the traditional Kaufman-type ion thruster,the cathode length should be shortened and the four-pole magnetic field configuration should be adopted;for the Annular ion thruster,increasing the cathode length and the width-diameter ratio of the discharge channel can improve the plasma uniformity,while increasing the number of magnets has little effect on the plasma distribution.The proposed Annular ion thruster configuration can improve the plasma uniformity well,but its macroscopic performance needs to be further optimized.Finally,based on the simulation results of the discharge chamber,the performance of ion optics under multiple operating conditions and the Annular ion thruster plume are studied.Meanwhile,a 3D particle model has also been developed for the Annular ion thruster plume.The results show that the nonuniform plasma distribution at the discharge chamber outlet will significantly affect the optics life.Moreover,under different plasma densities,the mechanism of accelerator grid Barrel Erosion and the effect of decelerator grid on the optics performance are also different.Therefore,the non-uniformity of plasma at the discharge chamber outlet must be considered in the simulation of optics.The plume distribution is sensitive to the initial distribution of beam ions,thus leading to the non-axisymmetric plume of Annular ion thruster.Hence,the simulation of the Annular ion thruster plume needs to be based on the 3D simulation results of the discharge chamber.In summary,the research work in this dissertation not only promotes the development of the simulation methods for the plasma in Kaufman-type ion thruster,but also deepens the understanding of the working mechanism and performance limitation of Kaufman-type ion thruster.It provides important reference and theoretical support for the design of Kaufman-type ion thruster.