星箭耦合系统多状态模型修正技术研究

在大型、复杂航天飞行器研制过程中,有限元分析发挥了重要作用。由于在建立有限元模型时进行了简化导致有限元模型不能真实的反映真实结构的特征。为了精确预示结构动态响应,需进行模型修正。针对全箭有限元模型修正特点,提出了多状态模型修正方法,并编制了相应的计算软件MPMU1.0。最后对某缩比模型进行了模态试验和模型修正,验证了方法的有效性。     

航天器在轨故障特征数据生成方法

针对故障特征数据模拟生成算法与航天器的原理、模型关联度高,航天器状态描述模型不成熟、难以应用于工程实践的现状,根据反映航天器在轨故障的遥测数据表现形式和变化时间长短,将航天器故障进行分类。从遥测数据变化的角度,针对每类故障遥测数据的变化特点,研究了符合每类故障数据变化规律的故障特征数据生成算法及基于WEB服务的故障特征数据生成原型系统实现方式。生成的故障特征数据在故障检测、诊断与预警等方面得到成功应用,使航天器对象、状态演化规则和测控信息产生等故障输入数据更接近真实的动态特征。     

跨声轴流压气机激波/泄漏涡/边界层分离相互作用的影响

对跨声速转子Rotor37进行三维定常数值模拟,将设计间隙与零间隙进行对比研究,分析激波、边界层分离、间隙泄漏涡相互作用影响.数值计算显示:激波、泄漏涡、边界层分离相互影响,加速了失速的发生;减小间隙可以起到扩稳的作用.根据边界层分离、间隙泄漏涡在叶栅高度上的影响范围,提出利用抽吸技术进行被动控制改善流道流动状况时抽吸点的设置位置.      

结构参数对火星探测用伞开伞性能的影响

文章以"火星探路者"所用伞为基础,对其结构作相应改变后进行充气过程仿真计算,研究结构参数对降落伞充气性能的影响。计算结果表明,盘缝带伞的阻力系数随着带宽和缝宽的增加而减小;但超声速开伞时,降落伞充气过程中伞衣的喘振现象随着带宽的增加而减弱,投影面积的波动随带宽增长变得缓和,这对盘缝带伞的开伞安全性和可靠性有利。     

水溶性芯模性能和应用研究

采用热压注成型工艺制备了一种新型水溶性芯模材料,研究了其密度、力学性能和水溶性能等,分析了影响该芯模材料力学性能的因素。结果表明,当固体填料石英砂为150目左右时,可获得性能最优的水溶性芯模。并将所制得的水溶性芯模成功地用于树脂基复合材料结构件的制造中。     

高速永磁无刷直流电机的热分析

为了解决高速永磁无刷直流电机温升过高带来的磁性能降低及绕组绝缘破坏等问题,对高速电机的温度分布及改进措施进行了一系列研究.采用集中参数法建立了电机热网络数学模型,推导出电机损耗、热导和温度之间的解析方程;建立了基于ANSYS/Workbench的电机三维有限元模型,对其进行稳态热分析,从而得到电机整体的温度分布,验证了电机热网络模型的正确性;提出了改变转子护套材料及电机轴打孔两种措施.分析结果表明:改进后的电机转子部分温度有了明显降低,其中护套温度降低了约34℃,永磁体约54℃,解决了电机的局部温度过高问题.     

Evaluation of using two-phase frictional pressure drop correlations for normal gravity to microgravity and reduced gravity

The calculation of two-phase frictional pressure drop (TPFPD) is required by two-phase systems operating under microgravity and reduced gravity. There are a large number of correlations for the TPFPD in tubes under normal gravity. However, it is hard to find out a TPFPD correlation obtained from microgravity and/or reduced gravity conditions, and thus people have to use TPFPD correlations for normal gravity to calculate TPFPD under microgravity and reduced gravity. It is necessary to evaluate the feasibility of such practice. This paper offers a comprehensive review of the TPFPD correlations for normal gravity and an up-to-data survey of the TPFPD experimental study under microgravity and reduced gravity. There are 23 TPFPD correlations for normal gravity reviewed and 135 experimental data under microgravity obtained from the literature. These experimental data are used to evaluate the reviewed TPFPD correlations. It is found that the smallest mean absolute relative deviation (MARD) of the correlations is greater than 34%. Using TPFPD correlations for normal gravity to reduced gravity and microgravity may be acceptable for the first approximation, but correlations intended for microgravity and reduced gravity are needed and more experiments are desired to obtain more data with high accuracy.     

Variations in the thermosphere and ionosphere response to the 17–20 April 2002 geomagnetic storms

The responses of the thermospheric density and ionospheric foF2 to the intense magnetic storms event on 17–20 April were analyzed by using data from CHAMP/STAR and ionosonde stations respectively, and NRLMSISE-00 and IRI-2007 models were used to simulate. The models can capture the tendency of changes, especially under quiet or moderate geomagnetic conditions, but are less accurate under geomagnetic storms. The thermospheric density is sensitive to the EUV emission and geomagnetic activity, and double-peak structure appeared in the dayside. On 19 April dayside, TADs traveled toward the equator with phase speeds of the order of 300–750 m/s, interfered near the equator to produce a total density perturbation of 25%, and then passed through each other and into the opposite hemisphere. For ionospheric foF2, there are non-symmetric hemispheres’ features during the intense geomagnetic activities. In details, middle latitudes in the north and high latitudes in both hemispheres are negative ionospheric storms, and the maximum amplitudes of δfoF2$\delta \mathit{foF}2$ is about 60%, but the amplitudes decrease from the higher to lower latitudes in the Southern Hemisphere. Meanwhile, the equatorial station shows positive phase, and the maximum value is about 100%. Finally, the mechanisms for these features will be discussed in this study.     

复杂涂覆目标的角闪烁特性分析

适当的涂覆材料可以使空中目标的后向雷达散射截面缩小,但同时,涂覆材料也会影响角闪烁偏差.为了充分利用涂覆材料的特性,利用图形电磁学和相位梯度法,在高频区对涂覆目标进行了角闪烁特性的建模与计算.鉴于图形电磁学的特色,涂覆目标的角闪烁计算不仅具有可视化特点,而且计算速度快、效率高.利用该方法对两球目标和复杂目标进行了仿真计算,计算结果表明涂覆材料在减小后向雷达散射截面的同时,对角闪烁具有一定的增强作用.      

仿真可信度评估中的AHP超越权重

AHP(Analytic Hierarchy Process)法在仿真可信度评估中经常使用,但传统的AHP法不能解决可信度评估结果的阶跃问题.为了解决这一问题,在明确了阶跃问题的主因是AHP相对权重的缺陷后,参考Petri网的相关定义,建立了AHP网的概念和数学基础;针对传统AHP相对权重的缺陷,进一步提出了增强型AHP网及相关定义、图例等;在网络定义的基础上,提出了AHP超越权重的概念及其数学表达式;确定了含有超越权重的AHP网节点取值算法和评估节点优先级算法;提供了一个应用AHP超越权重的仿真可信度评估实例,并获取了量化的评估结果.计算结果表明:含有超越权重的AHP体系能够解决可信度评估结果的阶跃问题.