Simulation of the effect of a magnetically insulated anode on a low-power cylindrical Hall thruster

The intersection point of the characteristic magnetic field line (CMFL) crossing the anode boundary with the discharge channel wall,and its influence on thruster performance and the energy and flux of ions bombarding the channel wall,have been studied numerically.The simulation results demonstrate that with the increase in distance from the crossover point of the CMFL with the channel wall to the bottom of the thruster channel,the ionization rate in the discharge channel gradually increases;meanwhile,the ion energy and ion current density bombarding the channel wall decreases.When the point of the CMFL with the channel wall is at the channel outlet,the thrust,specific impulse,and efficiency are at a maximum,while the ion energy and ion current density bombarding the channel wall are at a minimum.Therefore,to improve the performance and lifetime of the thruster,it is important to control the point of intersection of the CMFL with the channel wall.     

低温水热法制备形貌可控纳米α-Fe2O3的研究

以FeCl3.6H2O、尿素为主要原料,以聚乙烯吡咯烷酮(PVP)或十二烷基苯磺酸钠(SDBS)为表面活性剂,乙二醇为分散剂,采用低温水热法制备了不同形貌的α-Fe2O3,分析讨论了加入表面活性剂及乙二醇作为分散剂对产物形貌的影响,采用热重-差热分析(TG-DTA)研究样品的热分解过程,利用X射线衍射(XRD)、扫描电镜(SEM)对样品成分、粒度、形貌等进行了表征分析。结果表明:表面活性剂和分散剂可以控制颗粒的形貌,加入不同的表面活性剂、分散剂及控制其用量可以得到形貌不同的纳米α-Fe2O3。     

一种新型精密开关校验电源的研制

提出了一种开关型精密校验电源系统的实现方法,应用该方法研制的试验电源其输出精度达0.2%,输出相位、频率调节细度为0.01°和0.01Hz,完全满足系统应用要求。     

Effect of low-frequency oscillation on performance of Hall thrusters

In this paper,a direct connection between the discharge current amplitude and the thruster performance is established by varying solely the capacitance of the filter unit of the Hall thrusters.To be precise,the variation characteristics of ion current,propellant utilization efficiency,and divergence angle of plume at different low-frequency oscillation amplitudes are measured.The findings demonstrate that in the case of the propellant in the discharge channel just meets or falls below the full ionization condition,the increase of low-frequency oscillation amplitude can significantly enhance the ionization degree of the neutral gas in the channel and increase the thrust and anode efficiency of thruster.On the contrary,the increase in the amplitude of low-frequency oscillation will lead to increase the loss of plume divergence,therefore the thrust and anode efficiency of thruster decrease.     

零电压转换正激变换器开关管的应力分析

为了合理的选取零电压转换电路的谐振参数,利用Pspice对零电压转换正激电路进行了仿真分析,获得了电路参数与各开关管电压应力和电流应力之间关系的数据,并以此为基础优化选择了电路参数．     

基于WinCC的嵌入模糊PID控制在无水酒精工业过程控制中的应用

结合黑龙江省某无水酒精厂工程项目,提出了基于WinCC的嵌入模糊PID控制方法,WinCC嵌入C脚本程序实现模糊控制设定PID参数,PLC根据设定的PID参数利用集成的PID模块实现系统的高速控制,在不增加系统任何成本的情况下,实现了系统的智能控制,具有控制精度高,稳定性好,开发周期短的优点.     

Numerical simulation of the start-up process of a miniature ion thruster

A particle-in-cell Monte Carlo collision model of a discharge chamber is established to investigate the start-up process of a miniature ion thruster. We present the discharge characteristics at different stages (the initial stage, development stage, and stable stage) according to the trend of the discharge current with time. The discharge current is the sum of the sidewall current and the backplate current. During the start-up process, the sidewall current lags behind the backplate current. The variation and distribution characteristics of the discharge current over time are determined by the electron density distribution and electric potential distribution.     

Numerical study of the effect of aft-loaded magnetic field on multiple ionizations in Hall thruster

It is assumed that the shift of a strong magnetic field region with a positive gradient from exit plane to outside, namely the transit from a normal loaded magnetic field to an aft-loaded one, enhances the multiple ionization process in the magnetically shielded Hall thruster. To confirm this conjecture, a comparative study is carried out numerically with a particle-in-cell method. The simulation results prove that compared with the normal loaded magnetic field, the application of aft-loaded magnetic field enhances the multiple ionization process. This study further analyzes the ionization characteristics of the transition from low-charged ions to high-charged ions under two magnetic field conditions and the influence of the magnetic strength of aft-loaded magnetic field on the multiple ionization characteristics. The study described herein is useful for understanding the discharge characteristics of Hall thruster with an aft-loaded magnetic field.