| With the development of space electric propulsion technology and the proposal of All-Electric propulsion technology,electric thruster has been gradually expanded from single auxiliary propulsion to main propulsion,and its functions have been diversified from simplification.Due to the limitation of its structure and function,the traditional hall thruster cannot meet the requirements of diverse propulsion missions of future spacecraft,It is urgent to develop hall thruster technology with Wide Range Discharge Characteristics.The key problem to realize the high efficiency work of thruster with wide parameter range is the regulation of plasma distribution in the process of ionization and acceleration,the most critical starting point is to ensure to sufficient ionize of propellant gas under the wide range conditions.Based on this,this thesis designed a hall thruster principle prototype suitable for working in a wide range of parameters,and carried out a series of research and exploration on its discharge characteristics,the specific main works are as follows:First of all,the design of thruster prototype HEP-100 WR is completed based on the sufficient ionization criterion and with the core goal of being suitable for working in a wide flow range.Through the magnetic circuit structure of multi-pole and multicoil,the flexible control of the magnetic field is realized,and the characteristics of the magnetic field can move in a wide range of axial directions lay a foundation for the effective control of the axial position of the ionization region.At the same time,the continuous and gradually expanding ceramic channel structure provides a linearly varying cross section,which is compatible with the magnetic field with variable axial position,helping to optimize the ionization process.According to the method of adjusting flexible magnetic circuit,the desired magnetic field can be obtained successfully.Secondly,the ionization and acceleration process and discharge performance of HEP-100 WR were studied by PIC numerical simulation.It is found that the position of ionization region can be effectively controlled by adjusting the axial position of magnetic field peak,and the ionization effect is greatly improved when the ionization occurs in the region with small cross section of the channel.However,a longer acceleration distance and a smaller magnetic field curvature lead to serious wall collision loss during ion acceleration,which makes the performance of the low-flow condition not significantly improved after the position of magnetic field peak shifted inward.Thirdly,the discharge performance change rule of HEP-100 WR was mastered through experimental means,and its internal mechanism was analyzed by combining with plume parameters measured by probe.It is found that HEP-100 WR has a working point of optimal magnetic field position,and the position of magnetic field peak is located near the outlet of channel.Compared with the hall thruster with a uniform cross section channel,the HEP-100 WR performs better under medium-flow and high-flow conditions,while the performance under low-flow condition is not ideal.Both of them are closely related to the sufficient ionization of propellant gas and the wall collision loss of ions.In addition,the thesis also focuses on the discharge stability of HEP-100 WR,the experimental results show that this thruster has advantage in this aspect.Finally,in order to improve the discharge performance of HEP-100 WR under lowflow condition,the influence of channel configuration on the discharge characteristics of HEP-100 WR was studied.It is found that increasing the length of the straight tube section of the channel can improve the propellant gas density in the channel,promote the extending outward of high gas density area,effectively promote the ionization of propellant gas and ionization region to move outward,and thus comprehensively improve the discharge performance of HEP-100 WR,however,this method is only effective under low-flow condition.When the thruster works under medium-flow and high-flow conditions,the plasma density in the channel increases significantly,the wall collision loss of ions increases rapidly,and the electronic near-wall conduction effect also increases,which makes the thruster discharge performance deteriorate.At the same time,the straight tube length of ceramic channel has an optimal value,too short is difficult to improve the effect of propellant gas ionization and ionization region move outward,too long will intensify the wall collision loss of ions,when HEP-100 WR works with the optimal channel configuration,the wide range performance and stable working range of the thruster are significantly improved. |
