| Hall thrusters have the advantage of being high specific impulse,high efficiency and high reliability,making it more and more widely used in space propulsion.The anode is the key part of the Hall thruster to load the discharge voltage,receiving the electrons in the channel to form the discharge current and the axial acceleration electric field.Therefore,the state of the anode is one of the important factors that affect the performance level and discharge characteristics of the thruster,which also is a key indicator in designing work.In this paper,the influence of the anode ring and the gas distributor on the discharge behavior of the Hall thruster was studied.The following four parts were studied by means of numerical simulation and experimental combination:Firstly,the variation law and mechanism of the axial distribution of the anodic ring power during the change of the magnetic field and the gradient were studied.The understanding of the electronics transmit in the near-anode region under the control of magnetic field was established and the matching design of the magnetic field and the anode was carried out.The results show that the axial distribution of the anode ring temperature is not affected by the change of the magnetic field intensity,and the position of the temperature peak does not change,in the middle of the axial position.The reason is that the high-intensity bending magnetic field at the front end of the anode ring acts on the electrons,causing the electrons to settle along the curved magnetic field lines to the middle.However,the overall temperature of the anode ring decreases first and then increases with the increase of the magnetic field intensity,which is mainly affected by the decrease of the discharge current and the increase of the magnetic properties inherent in the Hall thruster.In addition,as the magnetic field gradient increases,the peak point of the anode ring temperature will gradually move toward the channel exit direction,and the overall temperature tends to decrease.The reason is that the increase of the gradient causes the move forward of the ionization zone in the channel,leading to the move forward of the electron deposition peak.The increase of the gradient increases the inelastic collision between gas distributor and zero magnetic point,and the energy is reduced,so that the deposition power of the anode ring is reduced.The results show that the design of the magnetic field near the anode is very important.Secondly,the mechanism of the three power supply modes of the anode and the gas distributor were studied.The influence of the discharge characteristics,the performance level and the heat flow transfer was analyzed,which could provide reference for the power supply design of the thruster.The results of the experiments and simulations show that the thrusters have the best effect in terms of discharge stability and performance when the thruster anode and gas distributors are energized.The main reason is the positive impact of the internal potential distribution of the thruster,the anisotropic distribution of electron energy and the ionization distribution.In addition,when the anode ring and the gas distributor are energized,the adjustment of the current distribution can be realized by the adjustment of the magnetic field,and the transfer of the current is carried out to realize the active temperature control of the key components of the thruster.The feasibility of active thermal control is verified by temperature measured under different current distribution.Thirdly,the relationship between the length of the anode ring and the magnetic field was studied.The influence of the length of the anode ring on the discharge of the thruster was analyzed,and the constraint condition of the length of the anode ring was established.The results show that there is an optimal length of the anode ring to optimize the performance of the thruster.The optimal value of the length of the anode ring obviously does not change when the magnetic field and the magnetic field gradient change.At this time,there is a significant advance in the ionization zone position.The comprehensive effect of the ion wall power loss and the ion acceleration optimizes the thruster performance when the ionization zone is moderate.When the anode ring is too long,there is a fundamental difference in the transmit form,which leads to the worse of acceleration of the electric field and the reduction of the electron energy,which further reduces the ionization of the thruster and the performance mutation.The results show that moderate anode ring can optimize the performance of the thruster.Finally,the influence of anode surface state on the discharge of the thruster was studied on the basis of the existing experiment and simulation.It was revealed that the phenomenon of the anode coating accompanied by the course of the experiment has obvious influence on the current distribution of the thruster.The anode surface difference was simulated by adjusting the supply voltage of the gas distributor and the anode ring,and the results show that when the anode ring and the gas distributor are energized,the electrons tend to deposit toward the gas distributor and the high energy electrons tend to deposit to the anode whose split ratio is small.The initial guess may be related to the position of the magnetic field in the channel.In addition,due to the lack of understanding of the inherent mechanism of the influence of the anode surface state on the discharge of the thruster,it is difficult to analyze the specific changes of the plasma parameters in the existing experimental conditions and simulation conditions.Therefore,the study of this issue put forward a number of prospects,providing the research direction and a certain reference basis for the next step to carry out the work. |
