PCAL信号多频点高效并行提取方法

PCAL(相位校准)信号通常用于消除VLBI(甚长基线干涉测量)观测设备的附加时延。随着更高观测精度要求的提出,基带信号带宽不断增大,所包含的PCAL信号频点个数也随之增加。传统的基于相关法的PCAL信号提取方法在处理多频点信号时,其计算量随着频点个数的增加而大幅增长,计算效率低。针对该问题,利用PCAL信号各频点之间的频率特性,提出了一种基于FFT(快速傅里叶变换)的PCAL信号多频点高效并行提取方法,并对2种方法的计算精度和计算量进行了对比分析。仿真结果表明:新方法的计算精度与传统方法相当;计算量不随PCAL信号频点个数的增加而增大;随着提取频点个数的增加,新方法计算效率优势明显。     

石英挠性加速度计测量航天器微振动的方法

利用高精度石英挠性加速度计可以测量航天器低频微振动,同时也可实现航天器在轨微角振动的间接测量。针对航天器特点,结合石英挠性加速度计工作特性,提出用高精度石英挠性加速度计测量航天器微振动的方法,给出微振动加速度、角加速度、角速度和角位移的不确定度分析,根据测量原理给出了各影响因素对测量合成不确定度的计算方法和分析结果。针对卫星敏感载荷的刚体平面测试环境,设计8个加速度计测点布局,开展了整星试验。试验数据分析表明:石英挠性加速度计可准确测量航天器的低频微振动(200 Hz以内),其直接测量和间接测量结果满足测量应用需求,线加速度测量分辨率为5μg,角位移测量分辨率为0.015″。     

空间润滑脂的研究进展

空间环境中高真空、高低温、强辐射、原子氧和微重力等恶劣因素对空间润滑脂的结构和性能提出了特殊要求。为了满足空间运动部件高可靠性和长寿命的要求,需要改善空间润滑脂的性能。文章主要从基础油、稠化剂和添加剂这3个方面介绍和分析了空间润滑脂的研究进展及发展方向。     

基于吊具吊点调节的航天器水平调节方法

水平调节是航天器吊装过程中质量控制和安全保障的重要环节。文章针对航天器吊装时不同状态的特点,提出了一种以传感器倾角为输入、吊点位置为输出的水平调节航天器的方法,并通过理论分析给出调节算法,最后通过软件仿真验证了新方法的有效性。     

Dynamical evolution of high area-to-mass ratio objects in Molniya orbits

For special demands, some notable orbit types have been developed by human, including the Molniya orbits, which have a relatively high eccentricity up to about 0.7, and a period of 12 h. Considering that space debris with high area-to-mass ratio (A/M) has been discovered, such objects may also exist in Molniya orbits due to spacecraft and upper stages fragmentation events. However, there are not sufficient studies of the complex dynamical phenomena of such orbits. These studies can enrich the knowledge about the long-term evolution of these orbits, be helpful to propose uncatalogued objects observation and identification, and also set the protected region as well as active debris removal. In this paper, the characteristics of 2:1 resonance of Molniya satellite orbits are studied. A large set of numerical simulations, including all the relevant perturbations, is carried out to further investigate the main characteristics, and special attention is payed to the dynamical evolution of objects with high A/M, particularly affected by the direct solar radiation pressure. The long-term dynamical evolution of orbital elements, as well as the dependency of lifetime on the A/M value, is discussed.     

多腔体气囊式回收系统的着陆冲击动力学建模与分析

首先对深空探测气囊式回收系统的结构特性进行了分析,讨论了多腔体气囊系统动力学分析模型的构造思路。然后引入一维流管理论描述子气囊之间气体流动的通气孔。最后通过气囊式回收系统着陆冲击过程的仿真分析了通气孔面积对系统着陆缓冲性能的影响,验证了通气孔模型的有效性。分析结果表明,本文建立的动力学分析模型能够较为全面地反映出气囊式回收系统的着陆冲击过程,分析出回收系统的各项工作参数或环境因素对系统着陆缓冲性能的影响。     

Design and Performance of an Improved Trapped Vortex Combustor

 A trapped vortex combustor (TVC) has been a very promising novel concept for it offers improvements in lean blow out, altitude relight, operating range, as well as a potential to decrease NO_x emissions compared to conventional combustors. The present paper discusses the improved designs of the new combustor over the prior ones of our research group, including that: a) the overall dimensions, both axial and radial, are reduced to those of an actual aero-engine combustor; b) the air flow distribution is optimized, and especially 15% of the air is fed into the liner as cooling air; c) a straight-wall diffuser with divergence angle 9癷s added. A series of experiments (cavity-fueled only, under atmospheric pressure) has been conducted to investigate the performance of the improved TVC. Experimental results show that at the inlet temperature of 523 K, the inlet pressure of 0.1 MPa, stable operation of the TVC test rig is observed for the Mach number 0.15-0.34, indicating good flame stability; the combustion efficiency obtained in this paper falls into the range of 60%-96%; as the total excess air ratio increases, the combustion efficiency decreases, while the increase of the inlet temperature is beneficial to high combustion efficiency; besides, the optimal Mach numbers for high combustion efficiency under different inlet conditions are confirmed. The outlet temperature profiles feature a bottom in the mid-height of the exit. This paper demonstrates the feasibility for the TVC to be applied to a realistic aero-engine preliminarily and provides reference for TVC design.     

圆形复合材料易碎盖定向分离

研究了复合材料易碎盖分离体定向抛出的策略。通过改变局部薄弱区搭接厚度和保持部分分离体与法兰边不刻断两种方式控制薄弱区强度,设计了4种不同薄弱区结构分布形式的复合材料易碎盖。对于薄弱区采用了可失效的弹塑性本构建立了不同薄弱区结构分布形式的复合材料易碎盖的有限元模型,并进行了冲破过程的数值仿真。根据数值仿真结果制作了其中两种结构形式的易碎盖并进行了模拟冲破试验。计算与试验结果表明了通过改变薄弱区的强度实现圆形复合材料易碎盖侧抛方案的可行性。     

直升机应急气囊充气及冲击着水过程数值分析

针对应急气囊充气展开过程以及直升机应急气囊冲击着水过程进行了数值模拟,得到了不同充气速率下气囊展开过程中内部压力分布情况,并根据气囊内压力变化规律,将气囊充气展开过程分为线性膨胀、深度膨胀和过度膨胀3个阶段,其中最大安全压力可为智能化充气控制提供阀值选择依据。同时,冲击着水受力状态和速度特性数值模拟结果与实验一致,可以用于应急气囊的工程设计。     

T型翼片的两种成型工艺

针对T型翼片的技术指标,依据应力分析结果,介绍了缠绕和铺层两种成型工艺,静力试验的结果表明:两种成型工艺均满足规定的均布载荷下、挠度小于200 mm的主要技术指标,通过对比两种工艺的优缺点,认为铺层工艺更适合该翼片的生产.