等离子体点火用高压电源设计方法研究

根据等离子体点火对高压直流电源的要求,选用具有电容型滤波器的LCC串并联谐振变换器为主电路拓扑结构,针对电感电流连续模式下的谐振变换器,在对其工作原理分析的基础上,用基波近似法推导出变换器的稳态模型,建立了变换器的等效电路,并给出了便于工程设计的电路的数学描述.通过研究各参数对电路性能所造成的影响,设计最优化的参数以保证开关管在全负载范围内实现零电压开关,有效降低了开关管的热损耗.详细介绍了电源系统的组成和电路参数的设计方法,针对该设计方案,通过仿真结果证实了理论分析的正确性.     

电帆推进在等离子体环境下推力影响因素分析和试验研究

为了分析电帆推力的影响因素，根据电帆推进原理设计了电帆地面模拟装置。首先分析了真空中带电导线和等离子作用机理，得出了电帆推力公式。利用朗缪尔探针测量了电帆模拟试验环境中等离子体参数，计算产生推力的大小，最后通过微推力测量系统测量电帆产生的推力，与计算结果进行了对比。根据推力公式和仿真结果表明，提高电压、增加带电粒子密度和速度、增加电帆长度均可增加推力。在试验中电帆上电压从300V增加到800V时，推力从9μN增加到26μN。仿真和试验结果表明，电压、带电粒子密度和速度、电帆导线长度都对推力有影响。根据试验结果，电帆推力公式的经验推力系数在1～2取值。     

Dynamic neighborhood genetic learning particle swarm optimization for high-power-density electric propulsion motor

To maximize the power density of the electric propulsion motor in aerospace application, this paper proposes a novel Dynamic Neighborhood Genetic Learning Particle Swarm Optimization (DNGL-PSO) for the motor design, which can deal with the insufficient population diversity and non-global optimal solution issues. The DNGL-PSO framework is composed of the dynamic neighborhood module and the particle update module. To improve the population diversity, the dynamic neighborhood strategy is first proposed, which combines the local neighborhood exemplar generation mechanism and the shuffling mechanism. The local neighborhood exemplar generation mechanism enlarges the search range of the algorithm in the solution space, thus obtaining high-quality exemplars. Meanwhile, when the global optimal solution cannot update its fitness value, the shuffling mechanism module is triggered to dynamically change the local neighborhood members. The roulette wheel selection operator is introduced into the shuffling mechanism to ensure that particles with larger fitness value are selected with a higher probability and remain in the local neighborhood. Then, the global learning based particle update approach is proposed, which can achieve a good balance between the expansion of the search range in the early stage and the acceleration of local convergence in the later stage. Finally, the optimization design of the electric propulsion motor is conducted to verify the effectiveness of the proposed DNGL-PSO. The simulation results show that the proposed DNGL-PSO has excellent adaptability, optimization efficiency and global optimization capability, while the optimized electric propulsion motor has a high power density of 5.207 kW/kg with the efficiency of 96.12%.     

Study of UV Ne II line shapes in the cathode sheath of an abnormal glow discharge

We report results of an experimental and theoretical study of complex UV line shapes of Ne II 369.421 nm, Ne II 370.962 nm, Ne II 371.308 nm, and.Ne II 372.711 nm lines in the cathode sheath (CS) region of an abnormal DC glow discharge in pure neon. Two sets of experimental profiles and electric field distributions, one for discharge with tungsten and the other with titanium cathode, were obtained by means of the optical emission spectroscopy (OES) and theoretically studied by the iterative CS kinetic model. It is shown that our theoretical model enables the determination of the most important CS parameters (e.g. the thickness of the CS region, and the theoretical distributions of electric field and gas temperature) and thereupon based accurate theoretical predictions of the experimentally observed profiles of the studied lines.     

Breakthrough detection in electrochemical discharge drilling to enhance machining stability

Film cooling holes are widely used in aero-engine turbine blades. These blades feature large numbers of holes with complex angles and require a high level of surface integrity. Electrochemical discharge drilling(ECDD) combines the high efficiency of electrical discharge drilling(EDD) with high quality of electrochemical drilling(ECD). However, due to the existence of a variety of energy for material removal, accurate and timely detection of breakthroughs is fraught with difficulties. An insuffic...     

基于数字孪生的航天电推进器优化设计方法

针对以引力波探测为代表的空间科学任务和以“国网星座计划”为代表的商用卫星网络任务对推进器的特殊需求，本文提出了一种基于数字孪生的推进器优化设计方法。该方法首先建立由机理模型模块和测试数据集模块组成的数字孪生体。机理模型模块依据推进器的物理过程建立模型，对难以测量的数据进行仿真模拟；测试数据集模块通过实验对推进器进行测试，依靠测试数据建立可测参数的数学模型。将数字孪生体与实验进行对比，通过对比结果反馈调节机理模块从而不断提高孪生体的准确性，最终为优化设计提供依据。结果表明：(1)该方法能够构建微波离子推进器的数字孪生体；(2)该数字孪生体的预测结果存在一定差异，通过分析发现该差异与机理模型的精细度以及测试数据集的数据量有关。     

电动膨胀循环液氧甲烷变推力发动机动态特性研究

电动泵压式液体火箭发动机受到了广泛的关注，然而电池有限的输出功率和过于沉重的质量成为限制电动泵压式发动机发展的重要因素。为此本文提出了一种电机驱动燃料泵和涡轮驱动氧泵的电动膨胀循环液体火箭发动机方案，并着重研究了该型发动机的动态响应特性。首先给出了20 kN级电动膨胀循环发动机的技术指标和部组件参数，进一步基于AMESim平台建立了全系统动力学模型，验证了方案的可行性和部组件动力学模型的准确性，并深入研究了单点工况和调节工况的动态响应特性。结果表明，针对启动过程而言，涡轮泵调整时间较电动泵长，这降低了系统响应速度，但工况越高，系统响应速度越快；高工况启动时，甲烷在冷却通道内的剧烈相变和跨临界状态的不连续物性相互耦合易引发系统振荡；就调节过程而言，推力调节时普遍存在超调或凹坑现象，且系统在两相同工况之间调节时，正调响应速度快于负调，这也导致阶跃幅值相等条件下的系统调整时间随目标工况升高而缩短。     

An atmosphere-breathing propulsion system using inductively coupled plasma source

CubeSats have attracted more research interest recently due to their lower cost and shorter production time. A promising technology for CubeSat application is atmosphere-breathing electric propulsion, which can capture the atmospheric particles as propulsion propellant to maintain long-term mission at very low Earth orbit. This paper designs an atmosphere-breathing electric propulsion system for a 3 U CubeSat, which consists of an intake device and an electric thruster based on the inductively coupled plasma. The capture performance of intake device is optimized considering both particles capture efficiency and compression ratio. The plasma source is also analyzed by experiment and simulation. Then, the thrust performance is also estimated when taking into account the intake performance. The results show that it is feasible to use atmosphere-breathing electric propulsion technology for CubeSats to compensate for aerodynamic drag at lower Earth orbit.     

Time resolved study of laser triggered electric discharge spark in atmosphere: Machine learning approach

In this paper we analyze the possibilities of using machine learning algorithms for analysis of optical spectra of electric discharge spark in atmosphere. Breakdown in air can be initiated by intense laser pulse, making plasma which has a significant electrical conductivity. The formed plasma can be further maintained by electric current obtained from capacitor discharge. In such a case the capacitor voltage can be much lower than the striking voltage (the voltage needed to initiate the electric breakdown in air). Present setup has timing precision and low jitter of fast laser and arbitrary high energies corresponding to capacitance and voltage to which the capacitor is charged. We have used a streak camera equipped with a spectrograph to analyze optical emission of plasma obtained in this way. Q-switched Nd:Yag laser was used to achieve the initial breakdown in air. Machine learning methods were used in order to classify optical spectra of plasmas with different electron temperatures obtained with different excitation energies. We have shown that, instead of using the usual way of identifying the spectral peaks and calculating their intensity ratio, it is possible to train the computer software to recognize the spectra corresponding to different electron temperatures. Principal component analysis was used to reduce the dimensionality of problem. We present possibilities of plasma electron temperature estimation based on several clustering algorithms.