Theoretial And Experimental Study Of Large Height Radius Ratio Hall Effect Thruster

Hall Effect Thruster (HET) is an electric propulsion device that has been widely used for various spacemissions, such as satellite attitude control, orbit trimming and transfering and power compensator, for its high-specific thrust, high efficiency and high reliability. Rich and successful flight application experience has proved that HET has advantages to serve as the main propulsion device. Therefore, designing high power and high performance HET will become one of major development directions. Current HETs designed based on similarity theory have structure characteristics of narrow channel width, large volume, and high weight, which cause the structure is not sufficiently optimized and hence the overall thrust-weight ratio is small. Meanwhile, the HET is operating with the low focusing level of plasma, the serve wall corrosion and plume divergence, which become the bottleneck restricting HET's spread and application. Therefore, in order to reduce HET weight, break the limitation of wall thickness deciding lifetime and suppress plume divergence, the design concept of Large Height Radius Ratio HET (LHRR-HET) is firstly proposed.In this paper, the similarity between turbine machine and HET is compared and the development history of structural design of turbine machine is surveyed and analogized to explain the origin of LHRR-HET design. On the basis of HET physical process in discharge channel, the general concept and characteristic parameter of LHRR-HET are given and some key problems are presented accordingly. These works point the way for the following research.The focal point of this paper is solving the problems raised by LHRR-HET design. Firstly, the increasing in channel width is one of distinguishing features of LHRR-HET. It weakens wall effect and further affects propulsion ionization. Through analyzing influence factors of the ionization process, the characteristic parameters are provided correspondingly. Changing channel width experiment is carried out to obtain the variations of ionization parameters after the width increased. Combining the results of two dimensional Particle-in-Cell (PIC) modeling based on Monte Carlo Collision (MCC) method, the important roles of the width change between two ceramic walls for electron energy balance process is analyzed. The variation of ionization area width and position caused by the differences of wall effect are explained accordingly.Secondly, experimental and numerical methods are employed to investigate the enhancing of annular effect caused by LHRR-HET design and further influence on acceleration process. Two basic elements, the formation of strong electric field in acceleration area and ion movement, are explicated for acceleration characteristic. Both of the ion motion feature and distribution are obtained in different annular effect. According to the dependence of electric field and electrons, electron hall drift and axial conductivity impacted by the radial distribution difference of magnetic field are analyzed. It is found that annular effect aggravation makes the ion acceleration worse. The physical mechanism of this phenomenon is also clarified.Thirdly, more attention is paid to the ion beam focus in discharge channel and plume, and especially, the control method of ion movement utilizing magnetic field design and optimization is studied. Two quantification parameters of magnetic field shape are put forward, which are magnetic field lines curvature and inclination angle. The matching relation between curvature and discharge voltage and the control method of plume divergence by inclination angle are discussed. These works play a positive role for restraining ion radial flow.Finally, base on the construction of one dimensional ion radial model, the relation between asymmetry of parameters radial distribution and height radius ratio is researched. Combining the survey results for height radius ratio of HET at home and abroad, the criterion of LHRR-HET is determined. A laboratory LHRR-HET is designed and its performance is tested. The results validate the feasibility of the LHRR-HET design concept.