基于自适应网格的钝头体激波诱导燃烧现象数值模拟研究

钝头体激波诱导燃烧是爆震研究的一个基本问题。针对化学恰当量比的H2/Air预混气在Ma=4.79和Ma=6.46时的激波诱导燃烧现象开展数值模拟研究，采用基于有限体积法的块结构自适应网格加密程序AMROC对带化学反应源项的轴对称Euler方程解耦求解，考察了数值模拟中不同形式的MUSCL重构格式、限制器类型以及化学反应机理等重要因素对模拟结果的影响。结果表明，程序能够根据设定的加密判据较好地实现网格自适应加密，减小总网格量，实现高效数值模拟。通过与实验数据的对比，表明非定常激波诱导燃烧算例的准确程度不仅取决于化学反应机理，也取决于限制器类型，而采用两种不同形式的MUSCL重构格式获得的振荡频率则几乎一致，与试验结果的误差分别为1.17%和0.97%。模拟对比经典的Jachimowski机理和近年来新发展的几种包含压力相关反应步的氢/氧反应机理，模拟结果表明：对于Ma=4.79时的非定常激波诱导燃烧模拟，经典的Jachimowski机理仍然是能够给出与实验结果最接近的反应机理；而对于Ma=6.46时的定常激波诱导燃烧模拟，几种反应机理均能给出与实验吻合较好的结果。     

基于等效电路模型与CDKF的锂离子电池荷电状态(SOC)估计

锂离子电池在社会生产各领域应用广泛,由于其复杂的电化学系统,状态检测难度较大,给供电保障带来不利影响.结合Thevenin等效电路与中心差分卡尔曼滤波法(CDKF),构建了一种聚合物锂离子电池的荷电状态(SOC)估计模型.MATLAB仿真验证表明,该模型能有效防止安时计数误差累积,电池SOC估计误差不超过5%.     

环氧树脂基复合材料加筋板结构吸湿行为研究

环氧树脂基复合材料的性能对湿热环境敏感，掌握该材料所组成结构的吸湿行为对其实际应用具有重要意义。通过以碳纤维环氧树脂基复合材料层合板的non-Fickian吸湿模型为基础，建立环氧树脂基复合材料加筋板结构的non-Fickian吸湿模型，在70℃/85% RH湿热条件下开展加筋板结构的吸湿实验，对所建立模型进行验证，并与已有的加筋板吸湿模型进行对比，通过所建立模型给出了加筋板沿厚度方向的吸湿量分布规律。结果表明:所建立加筋板non-Fickian吸湿模型的计算结果与实验结果吻合良好，在整个吸湿阶段相对误差小于5%，模型的预测精度高于传统Fick模型。所建立的加筋板non-Fickian吸湿模型可用于环氧树脂基复合材料加筋板层合结构吸湿量的准确预测。      

磁浮飞行风洞试验技术及应用需求分析

随着高速、超高速轨道交通的快速发展,需要发展新型的风洞设备,实现风洞性能和试验能力的突破.磁浮飞行风洞是利用真空管道列车概念结合动模型试验技术提出的一种新概念风洞设备,可以构建出更加接近真实状态的测试环境.本文从磁浮飞行风洞基本概念、国内外研究现状及发展趋势、试验技术、应用需求等几个方面开展论述.首先论述了国内外传统风洞和动模型设备的现状及发展趋势,指出了发展磁浮飞行风洞的必要性;其次,重点对磁浮飞行风洞需要发展的试验技术进行了分析;最后,对磁浮飞行风洞在超高速轨道交通及其他领域的应用需求进行了展望.     

Scientific objectives and payloads of Tianwen-1, China’s first Mars exploration mission

This paper describes the scientific objectives and payloads of Tianwen-1, China’s first exploration mission to Mars. An orbiter, carrying a lander and a rover, lifted-off in July 2020 for a journey to Mars where it should arrive in February 2021. A suite of 13 scientific payloads, for in-situ and remote sensing, autonomously commanded by integrated payload controllers and mounted on the orbiter and the rover will study the magnetosphere and ionosphere of Mars and the relation with the solar wind, the atmosphere, surface and subsurface of the planet, looking at the topography, composition and structure and in particular for subsurface ice. The mission will also investigate Mars climate history. It is expected that Tianwen-1 will contribute significantly to advance our scientific knowledge of Mars.     

PBT弹性体微相分离及对其力学性能的影响研究

为了获得微相分离对宽温PBT叠氮聚醚弹性体力学性能的影响规律,用红外光谱分析法(FT-IR)和动态热力学分析法(DMA)研究了PBT叠氮聚醚弹性体产生微相分离的机理和影响因素。用调节硬段含量、交联参数的方法调控其微相分离,控制适当的微相分离程度可显著改善推进剂的力学性能。研究结果表明:在二元醇扩链的弹性体体系中,当硬段含量约为15%时,弹性体发生相对最大比例的微相分离,体现出较佳的综合力学性能。通过微相分离的调控可获得宽温范围内综合力学性能较好的叠氮聚醚推进剂用粘合剂基体材料。     

Countermeasure Against Regenerative and Forced Chatter of Flexible Workpieces in Milling Processs Using Bi-directional Excitation

A novel extended methodology for chatter suppression in milling process by applying external forced vibrations to the workpiece in two orthogonal directions which are the feed and cross-feed directions.Both the regenerative and forced chatter suppression during the milling process of flexible workpieces are investigated.Here,the workpiece is subject to a sinusoidal periodic force in the feed direction to disrupt the regenerative effect.Additionally,to minimize the forced chatter,the workpiece is subject to the periodic excitation force in cross-feed direction.This force is proportional to the magnitude of the estimated cutting force in cross-feed direction and has a phase opposite to the cutting force to minimize the vibration amplitudes.The effectiveness of the proposed method is evaluated numerically and experimentally,for the spindle speed located in both the local minima and local maxima of the stability lobe diagram.The numerical simulations indicate significant suppression effect in terms of vibration amplitudes,resulting in suppression of both the regenerative chatter and the forced chatter.Experiments were conducted by using a workpiece-mounted active stage composed of flexure hinges and driven by piezoelectric actuators.The experimental results agree qualitatively with the numerical simulations.The proposed method indicates a remarkable vibration reduction effect for both regenerative and forced chatters.     

Design of Interplanetary Transfers with Passive Gravity Assists and Deep Space Maneuvers

In the paper, the problem of designing interplanetary trajectories with several swing-bys and deep-space maneuvers is solved using the method of virtual trajectories developed by the authors. The algorithms for the calculation of both heliocentric and planetocentric trajectory arcs are presented, including the case of resonant trajectories. The results of applying the method of virtual trajectories to the problem of designing an interplanetary transfer to Jupiter are given and compared with the baseline trajectories for the Juno, Europa Clipper, and Laplace missions.     

收集处理方法对含铝固体推进剂凝相燃烧产物特性影响

含铝固体推进剂凝相燃烧产物特性对固体火箭发动机的燃烧效率、燃烧稳定性和绝热安全性等影响重大。为获得准确可靠的凝相燃烧产物的理化特性,利用定压燃烧装置来收集凝相燃烧产物,采用马尔文激光粒度分析仪、扫描电镜及X射线衍射仪对产物进行表征,研究收集介质、干燥处理和超声分散对凝相燃烧产物性质的影响。结果表明,使用水收集获得的凝相燃烧产物平均粒度与氮气收集条件下相比大60%,水收集法适用于研究推进剂近燃面凝相燃烧产物。干燥处理能保证凝相燃烧产物样品中大尺寸颗粒的有效取样,在粒度测试之前需要对样品进行干燥处理来获取准确的凝相燃烧产物粒度分布数据。超声分散会导致大颗粒团聚物含量降低,小颗粒团聚物含量升高,最终显著降低凝相燃烧产物平均粒径。粒度测试时,在80kHz条件下,超声分散参数设定为40 W,5 min较为合适。基于研究结果,提出了一套科学合理的凝相燃烧产物收集处理方法。     

磁场对高电压霍尔推力器性能影响研究

为研究磁场构型、磁场强度对高电压霍尔推力器主要性能的影响机理,以HET-200推力器为对象,采用固定磁场构型和不固定磁场构型两种方案进行实验研究。结果表明,在不固定构型的情况下增强磁场,放电电流存在两个极小值,效率也存在相应的两个极大值;但当固定磁场构型时,则放电电流只有一个最小值,效率也只有一个最大值。以最优效率下的磁场构型为基准,获得了磁场与电压、磁场与流量的匹配关系分别为B_(r, max)∝V~(0.7),B_(r, max)∝m。