增强高超声速化学反应流数值计算的稳定性方法

针对高超声速化学反应流数值模拟中包含源项对角化雅可比矩阵的数值格式稳定性很差的问题,在对采用上下对称的高斯-赛德尔(LU-SGS)格式的离散方程进行线性稳定性分析的基础上,提出一种依据流动状态对流场的块网格进行局部加密的方法,以增强流场数值计算稳定性。在高超声速流场中,对包含激波后亚声速高温区域的块网格给予加密,而其他区域中的块网格可以适当进行网格粗化或保持不变。算例结果表明,相比于初始网格,局部加密后的改进网格并不会产生过多的网格量,而且能够采用较大的柯朗-弗里德里奇-列维（CFL）数以达到数值求解过程中稳定计算和快速收敛的目的。     

基于广义Richardson外插方法的阻力预测精度分析

利用计算流体力学(CFD)方法预测阻力是飞行器气动设计中的关键环节。采用广义Richardson外插方法分别对数值方法预测二维简单构型的压差阻力、摩擦阻力和三维复杂构型的总阻力的精度进行了分析。在NACA 0012翼型无黏绕流和平板湍流边界层两个算例中验证了NSAWET程序和广义Richardson外插方法,分别得到数值算法预测压差阻力和摩擦阻力能达到的名义精度。进而模拟三维通用研究模型(CRM)翼身组合体绕流,得到的阻力名义精确值在DPW 5的统计误差带范围之内;综合DPW 5的计算结果来看,不同CFD解算器的结果之间存在一定差别,阻力预测精度总体上不符合二阶。可见,标准Richardson方法采用的二阶精度假设难以普遍适用,有必要采用广义Richardson外插方法得到名义精度。针对不合理的名义精度,采用Roache建议的方法加以限制。广义Richardson外插方法有助于提高误差分析的合理性,可以进一步降低网格对阻力预测的影响。     

Predicting atmospheric delays for rapid ambiguity resolution in precise point positioning

Integer ambiguity resolution in precise point positioning (PPP) can shorten the initialization and re-initialization time, and ambiguity-fixed PPP solutions are also more reliable and accurate than ambiguity-float PPP solutions. However, signal interruptions are unavoidable in practical applications, particularly while operating in urban areas. Such signal interruptions can cause discontinuity of carrier phase arc, which introduces new integer ambiguities. Usually it will take approximately 15 min of continuous tracking to a reasonable number of satellites to fix new integer ambiguities. In many applications, it is impractical for a PPP user to wait for such a long time for the re-initialization. In this paper, a method for rapid ambiguity fixing in PPP is developed to avoid such a long re-initialization time. Firstly, the atmospheric delays were estimated epoch by epoch from ambiguity-fixed PPP solutions before the data gap or cycle slip occurs. A random walk procedure is then applied to predict the atmospheric delays accurately over a short time span. The predicted atmospheric delays then can be used to correct the observations which suffer from signal interruptions. Finally, the new ambiguities can be fixed with a distinct WL-LX-L3 (here LX denotes either of L1, L2) cascade ambiguity resolution strategy. Comprehensive experiments have demonstrated that the proposed method and strategy can fix zero-difference integer ambiguities successfully with only a single-epoch observation immediately after a short data gap. This technique works even when all satellites are interrupted at the same time. The duration of data gap bridged by this technique could be possibly extended if a more precise atmospheric delay prediction is found or on-the-fly (OTF) technology is applied. Based on the proposed method, real-time PPP with integer ambiguity fixing becomes more feasible in practice.     

基于微分Petri网的民机航迹演化通用模型构建

为实现对未来大流量、高密度、小间隔条件下的空域实施管理,在战略航迹规划阶段,提出了一种模块化的战略航迹演化通用模型。建立了不同航段之间航空器状态动态切换的一类宏观Petri网演化模型,以及同一航段内航空器速度和高度两种特征参数值连续变化的3类微观Petri网演化模型。根据航空器特征参数值转化的4种不同形式并基于航空器全飞行剖面的混杂运行特性,运用微分Petri网理论,定义了航空器的4种演化模式,通过组合各种演化模式得到了3种航空器基本演化模型。在满足航空器性能约束的前提下,通过设定10个航段及15个高度和速度预设值,得到了全飞行剖面下各特征参数的演化图。结果表明,所设计的演化模型增强了航迹预测模型的通用性,能够反映航空器在水平剖面和垂直剖面内的状态变化。     

预估太阳电池阵在轨最高温度的经验公式

针对距地高度为300～1000 km的太阳同步轨道,分析了一维转动展开式太阳电池阵的温度影响因素,给出了计算太阳电池阵最高温度的经验公式。此公式同样适用于低地球轨道的卫星,且计算结果可包络卫星热控状态变化带来的影响,在太阳电池阵设计阶段可为电源分系统提供太阳电池阵最高温度的初步数据。     

空间站舱内噪声评价与降噪技术现状及建议

空间站舱内噪声对航天员危害严重,必须对其进行严格控制。文章首先分析了适用于空间站噪声评价的指标以及主要噪声源特点;总结了空间站的噪声预测方法和不同方法适用的频率范围、局限性;介绍了国际空间站的降噪工作,总结了其中的经验和不足;最后结合我国空间站噪声控制的研究现状,对我国空间站降噪工作提出了建议：降噪工作必须贯穿空间站设计、制造和在轨工作的整个过程,才能对噪声进行有效控制。     

碳布叠层穿刺复合材料多尺度传热特性研究

为了深入认识复合材料的多尺度传热特性,预测复合材料宏观热物性参数,基于通用单胞思想和多尺度传热特性分析,建立了一种有效预测碳布叠层穿刺复合材料等效热物性参数的方法。基于电镜扫描分析了纤维束和编织结构的特征,采用通用单胞思想,建立了介/细观传热分析模型,通过数值仿真进行了一系列的多尺度传热特性分析,譬如:纤维体积分数对纤维束结构传热特性的影响、穿刺纤维束大小对编织结构传热特性的影响分析,在此基础上,建立了胞体模板扩展,初步将介/细观结构研究规律应用到宏观结构热物性预测,并进行多层胞体传热特性分析。验证实验表明:等效热物性预测值与实验值吻合较好,方法有效,为深入理解认识碳布叠层穿刺复合材料的介/细观传热特性提供了有效的分析手段。     

Characterization and life prediction of single-pass honing tool for fuel injection nozzle

Single-pass honing is an important machining method for finish machining of holes, which can meet the requirement for high efficiency and consistency of holes. Characterization and life prediction of single-pass honing tool are necessary to improve the machining accuracy of holes honed, especially dimension accuracy. Single-pass honing tool is a single layer abrasive tool with fixed dimension, which still remains problematic for characterization and life prediction. For fuel injection nozzles with bore diameter under 1 mm, the stiffness of the single-pass honing tool is poor. This article presents a novel analytical model that predicts life of the tool with poor stiffness. Firstly, according to the bore diameter and dimension tolerance, the single-pass honing tool is designed and manufactured. Based on the prepared single-pass honing tool, the measurement and characterization methods are established. Furthermore, the tool wear tests are carried out, and the tool contour evolution model is established to predict the tool life.     

直/气复合控制导弹的模型预测和自抗扰姿态控制设计

针对直/气复合控制导弹姿态控制系统的特点,提出将非线性模型预测方法与自抗扰控制方法结合的姿态控制策略,设计姿控脉冲发动机阵列点火逻辑,在分析直接侧向力有限约束集的基础上提出直/气复合控制导弹姿态控制系统设计方法。仿真结果表明,所给出的复合控制策略可以有效抑制外部干扰和模型不确定性的影响,显著加快拦截导弹的过载响应速度。     

计量活门磨损寿命预测

对计量活门的磨损量进行建模,进行了探索研究,考虑了3种计算磨损量的方法.基于某型航空发动机燃油控制装置的计量活门试验数据的计算,结果表明:采用灰色理论的基于时间序列的一阶微分方程模型可以较准确地计算出计量活门的磨损量,相对误差小于5%.对于燃油控制装置计量活门磨损寿命的预测具有实用意义, 可以为燃油控制装置整体使用寿命的提供一定的依据.