高平尾布局飞机深失速特性及失速改出伞数值计算与分析

ARJ21飞机是我国自行研制的具有典型T尾布局特点的先进支线飞机。失速和失速特性试飞是ARJ21飞机适航取证试飞最重要的试飞项目之一。高平尾(T尾)布局飞机可能存在深失速运动模态,给飞机的失速特性试飞带来安全风险。本文首先分析了高平尾(T尾)布局飞机的空气动力学特点,剖析了"深失速"现象的产生原因,并在此基础上以ARJ21飞机为算例,结合具体的风洞实验数据库,应用工程估算的方法对动导数进行了补充完善,其次建立了适合预测飞机失速和深失速运动方程的空气动力学模型,并对飞机的运动特性特别是深失速特性进行了仿真计算,计算结果与实际试飞结果取得了较好的一致性;最后选择深失速状态作为失速改出伞设计的临界状态,建立失速改出伞的数学模型,对失速改出伞改出深失速的动态过程进行了仿真计算,验证了失速改出伞改出深失速的设计参数,为失速改出伞的研制提供了参考依据。     

基于概率网格Hough变换的多雷达航迹起始算法

 针对常规Hough变换(THT)航迹起始算法采用二元积累的弊端,提出了一种按测量点迹分布概率进行积累的多雷达航迹起始算法。首先把观测空间划分为统一大小的网格,然后根据雷达测量精度计算出观测数据落在每个网格内的概率,进而得到每个网格存在目标的概率,最后的Hough积累采用网格概率进行加权。与常规Hough变换法相比,新算法起始的航迹具有更高的精度和更好的鲁棒性,适合于不同精度雷达的联合航迹起始。仿真结果验证了算法的有效性。     

航空发动机球轴承热分析

在动力学分析的基础上,对航空发动机高速球轴承进行了热分析。首先在润滑模型分析的基础上,对球轴承的生成热速率作了分析计算。通过对球轴承中复杂的传热关系研究,进而采用有限元法、系统平衡法和经验公式相结合的方法计算了球轴承系统的温度分布。在温度场计算中,对内热源的分配和边界条件的处理进行了深入研究。最后对某发动机主轴球轴承进行了计算,结果和606研究所提供的试验数据基本相符,其误差不大于百分之五。      

一种离心压气机子午流道的优化成形方法

利用S₂反问题的数值计算,发展了一种通过合理调整压力分布来确定优化子午流道形式的实用方法。优化的两个原则是尽量减少附面层分离和减小作为引起二次流主要原因之一的子午流道内的法向压差。设计了两种自动生成优化流道的方案,并将相应的程序用于实际离心压气机的优化设计,比较了子午流遭轮毂轮整处的压力分布,表明所用的方法达到了予期的效果。      

自旋卫星红外地中脉冲丢失情况下姿态确定分析与应用

实际应用中,由于遥测故障或脉冲重叠等多种原因,获取姿态脉冲信息时,可能缺少某些测量脉冲,为姿态确定的方法选择造成一定难度。针对海上测量弧段,某自旋卫星在红外地中脉冲丢失,仅有地出脉冲以及太1、太2脉冲时的几何定姿方法问题,通过对其原理、概念进行分析,制定自旋卫星红外地中脉冲丢失情况下定姿的方案与方法。该方法主要用于海上实时姿态监视,应急情况下也可以用于姿态的粗控。该研究为航天测量船应用测控软件的设计提供了良好基础。     

Solar modulation of galactic cosmic radiation

In this review an attempt is made to present an integrated view of the solar modulation process that cause time variation of cosmic ray particles. After briefly surveying the relevant large and small scale properties of the interplanetary magnetic fields and plasma, the motion of cosmic ray particles in the disordered interplanetary magnetic fields is discussed. The experimentally observed long term variations of different species of cosmic ray particles are summarised and compared with the theoretical predictions from the diffusion-convection model. The effect of the energy losses due to decelaration in the expanding solar wind are clearly brought out. The radial density gradient, the modulation parameter and their long term variation are discussed to understand the dynamics of the modulating region. The cosmic ray anisotropy measurements at different energies are summarised. At high energies (E 1 GeV), the average diurnal anisotropy is shown to be energy independent and along the 18.00 h direction consistent with their undergoing partial corotation with the sun. The average semi-diurnal anisotropy seems to vary with energy as E ⁺¹ and incident from a direction perpendicular to the interplanetary field line, consistent with the semi-diurnal component being produced by latitudinal gradients. Both the diurnal and semi-diurnal components are shown to be practically time invariant. On a day to day basis, however, the anisotropy characteristics such as the exponent of variation, the amplitude and the phase show very high variability which are interpreted in terms of convection and variable field aligned diffusion due to the redistribution of the galactic cosmic ray density following transient changes in the interplanetary medium. The anisotropy observation at low energies (E 100 MeV) are, however, not explained by the theory.The rigidity dependence and the anisotropies during short term variations such as Forbush decreases are discussed in terms of the proposed field models for the interplanetary field structure and are compared with the observed rigidity dependence of long term variations. The data pertaining to the 27 day corotating Forbush decreases and their association with enhanced diurnal variation are also presented. The relationship between the energetic storm particle events which are caused by the acceleration of particles in the shock fronts and the Forbush decreases which are caused by the exclusion of galactic particles by the enhanced field structure in the same fronts are clearly brought out. Thus the recurrent increases at low energies and recurrent decreases at high energies may both be caused by the field structure in the shock front. In conclusion, the properties of the very short period fluctuations (18–25 cph) are summarised.     

跨音速压气机叶栅流动有粘-无粘相互作用的迭代计算

 本文利用较为先进的附面层内法向速度分布等半经验相关式,发展了一种适用于大逆压梯度的附面层积分方法。将激波近似地用大逆压梯度代替,对湍流附面层进行了快速计算,再将求得的附面层参数与无粘主流计算通过建立适当的数学模型结合起来,反复迭代后将计算结果与实验数据及无粘计算的结果比较,可以看出有粘-无粘迭代对无粘计算结果有明显改进。     

拉杆转子力学模型的研究

 提出了一种力学模型。该力学模型刻画了拉杆转子各部件之间在相互联接处的力学状态和性质。用动态子结构方法时一试验模型拉杆转子进行了理论计算,同时在实验室对模型拉杆转子的固有频率进行测试。由计算和试验的对比分析表明,这种力学模型较好地反映了拉杆转子系统的物理本质。     

Bispectral analysis of atmospheric radar signals

The bispectral analysis techniques have been applied on signals received from the back-scattered signals by the MST radar. The results of this analysis are compared with that of the conventional power spectral analysis using the Fast Fourier Transform (FFT) technique. Our results showed that there is a significant advantage in using the bispectral technique over the conventional FFT technique. This study focuses on the importance of bispectral analysis in applications to atmospheric signals.