天线窗缝隙流传热的实验研究

在马赫数为５．０和７．８，相应的单位长度雷诺数为４．７×１０７／米和３．５×１０７／米气流条件下，测量了天线窗与相邻防热层间缝隙的热流率分布，以研究局部外流场、缝隙尺寸及其取向对天线窗缝隙内热环境的影响。     

Numerical Modeling of the Ring Current and Plasmasphere

Over the last 25 years, considerable scientific effort has been expended in the development of quantitative models of the dynamics of Earth's inner magnetosphere, particularly on studies of the injection of the storm-time ring current and of dynamic variations in the shape and size of the plasmasphere. Nearly all modeling studies of ring-current injection agree that time-varying magnetospheric convection can produce approximately the ion fluxes that are observed in the storm-time ring current, but the truth of that assumption has never been demonstrated conclusively. It is not clear that the actual variations of convection electric fields are strong enough to explain the observed flux increases in ~100 keV ions at the peak of the storm-time ring current. Observational comparisons are generally far from tight, primarily due to the paucity of ring-current measurements and to basic limitations of single-point observations. Also, most of the theoretical models combine state-of-the-art treatment of some aspects of the problem with highly simplified treatment of other aspects. Even the most sophisticated treatments of the sub-problems include substantial uncertainties, including the following: (i) There is still considerable theoretical and observational uncertainty about the dynamics of the large-scale electric fields in the inner magnetosphere; (ii) No one has ever calculated a force-balanced, time-dependent magnetic-field model consistent with injection of the storm-time ring current; (iii) The most obvious check on the overall realism of a ring-current injection model would be to compare its predicted Dst index against observations; however, theoretical calculations of that index usually employ the Dessler-Parker-Sckopke relation, which was derived from the assumption of a dipole magnetic field and cannot be applied reliably to conditions where the plasma pressure significantly distorts the field; (iv) Although loss rates by charge exchange and Coulomb scattering can be calculated with reasonable accuracy, it remains unclear whether wave-induced ion precipitation plays an important role in the decay of the ring current. However, considerable progress could be made in the next few years. Spacecraft that can provide images of large regions of the inner magnetosphere should eliminate much of the present ambiguity associated with single-point measurements. On the theoretical side, it will soon be possible to construct models that, for the first time, will solve a complete set of large-scale equations for the entire inner magnetosphere. The biggest uncertainty in the calculation of the size and shape of the plasmasphere lies in the dynamics and structure of the electric field. It is still not clear how important a role interchange instability plays in determining the shape of the plasmapause or in creating density fine structure.     

燃烧室中平均流速对速度耦合与压力耦合的影响

对热力发动机中存在的线性振荡燃烧的研究，通常假设速度耦合与压力耦合的作用独立无关且作用结果可以线性相加。本文通过对压耦合与速度耦合现象的分析，说明了使这一假设不合理的平均流速界限，并给予了实验证明。     

飞机前起落架支柱旋转机构角度及角速度测试方法的优化

本文介绍一种利用步进电机驱动某系列飞机前起落架操纵机构,在套筒与支柱旋转机构处采用平行四连杆结构的工装,利用旋转编码器实现操纵机构与支柱旋转机构角度与角速度精确测量的优化测试方法,并成功应用于测试设备。     

一种基于新三维随机Hough变换的航迹起始算法

针对雷达跟踪多目标时,目标点迹受杂波、噪声等因素影响,航迹起始难度大的问题,利用三维空间直线表示方法提出了一种4参数三维Hough变换算法.该算法是对传统二维Hough变换的拓展,它结合了传统的二维随机Hough变换理论,是一种新的三维随机Hough变换算法.通过该算法对理论数据和实测数据进行验证,结果表明,对于航迹区别较大的目标,该算法的航迹起始成功概率为98.5％;对于空间航迹相近的目标,该算法可成功将目标航迹从杂波中提取出来,虽然可能会出现航迹混淆,但利用目标先验信息可解决该问题,实现航迹起始.     

水平携带床内玉米秸颗粒速度场的PIV实验研究

为研究生物质颗粒在水平携带床中的流动特性,搭建了水平携带床透明模拟装置.利用PIV无接触测量技术,在氩气流量为1.9 m3/h工况下,对60~160目粒径的玉米秸颗粒流进行了速度场的研究.计算出了颗粒和氩气的平均速度以及流经水平携带床的时间,对颗粒与氩气的跟随性进行了分析.研究结果表明,颗粒流的轴向速度沿轴方向不断增大,管道中心附近的颗粒加速最为明显,而边壁附近的颗粒速度变化相对较慢;颗粒流的速度沿径向大致呈抛物线状分布;颗粒流的平均运动速度比氩气低,颗粒流通过水平床的平均时间略大于氩气.     

典型水文环境下航空声呐浮标双基地作用范围

航空声呐浮标双基地探测是应对水下目标声隐身能力持续提高的有效技术途径之一。分析了航空声呐浮标的指标,给出了双基地声呐配置,采用双基地声呐方程为依据,利用数值仿真的方法计算了 3种典型海洋环境条件下双基地声呐浮标探测范围,讨论了海洋环境对双基地声呐探测的影响,为航空声呐浮标双基地战术使用奠定技术基础。     

延伸喷管展开ADAMS动力学仿真

利用机械系统动力学仿真分析软件ADAMS进行延伸喷管展开动力学仿真,在已知延伸喷管结构尺寸、各部件质量特性、作动筒内压力及各种展开阻力的条件下,计算了延伸锥展开位移、速度和加速度。并与试验结果比较,两种结果接近。对计算结果分析得知,在保证展开时间满足要求的前提下,适当降低展开速度并尽可能匀速展开,可以减小展开过程中延伸锥与基础喷管之间的撞击力;为了保证展开可靠性,作动筒的展开力应有一定持续时间,尽量避免出现压力峰后压力突降。对固体火箭发动机延伸喷管设计与研究具有重要意义。     

穿孔管式扩散器出口流速均匀性研究

为解决穿孔管式燃油扩散器内部压力分布严重不均匀,导致燃油扩散器出口流速不符合要求的问题对穿孔管式扩散器出口流速均匀性开展研究。以 Matlab 及 Fuent 软件为平台,通过 Sparlar-Allmaras 湍流模型来处理燃油在扩散器内的三维流动,建立穿孔管式扩散器内部燃油流动模型,并分析其内部压力分布及出口处的速度分布。多次选代计算后,发现网孔开设及内部构型设计可有效调节内部的流动方式和压力分布。其中网孔开设方面应考虑开孔总面积足够大:另外,对内部构型进行修型,在扩散器内部适当位置添加合适高度的孔板。详细给出了网孔的开设方法及扩散器内部需重点考虑的3个关键孔板的设计规律,对穿孔管式燃油扩散器的设计及优化提供了理论参考。     

基于速度积分匹配的旋转调制惯导系统动基座对准方法

卫星导航信息辅助动基座对准过程中,速度噪声会影响对准精度和快速性,制约了旋转调制惯导角秒级高精度快速对准的实现.针对这一问题,提出了一种基于旋转调制惯导速度积分匹配的快速动基座对准方法,通过建立旋转调制惯导动基座对准误差方程和卡尔曼滤波观测模型,以消除动基座对准对载机特殊运动的要求.最后,在实验室静态环境和车载环境下,分别开展了速度积分匹配和速度十位置组合导航动基座对准仿真实验.仿真结果表明,提出的速度积分匹配方法具有误差估计量收敛速度快的特点,在对准精度不降低的情况下相对组合导航匹配方式能有效缩短动基座对准时间,并能基于旋转调制惯导取消动基座对准对载机的机动需求.