Experiments of effects of inlet-air distortion on aerodynamic performance in transonic compressor

The inlet-air distortion which was caused by high angle-of-attack flight was simulated by plugboard.Experiments were conducted on a transonic axial-flow compressor's rotor at 98% rotating speed.The flow-field characteristics and mechanism of performance degradation were analyzed in detail.The compressor inlet was divided into four sectors at circumference under inlet-air distortion.They were undistorted sector,transition sector A where the rotor was rotating into the distortion sector,distorted sector and transition sector B where the rotor was rotating out of the distortion sector.The experimental results show that compared with undistorted sector,there is a subsonic flow in transition sector A,so the pressure ratio is decreased by a large margin in this sector.However, the shock wave is enhanced in distortion sector and transition sector B, and thus the pressure ratio increases in these sectors.Because of the different works at circumference,the phase angle of total pressure changes 90° when the inlet total pressure distortion passes through compressor rotor.In addition,the frequency and amplitude of disturbances in front of the rotor strengthenes under inlet distortion,so the unstable flow would take place in advance.In addition, the position of stall inception is in one of the transition sectors.      

偏场使用的同轴三反系统畸变稳定性仿真分析

针对测绘图像几何精度对光学镜头畸变稳定的要求,仿真分析了一偏场使用的同轴三反光学系统镜头的畸变稳定性,从而论证该光学镜头用于测绘相机的可能性。将光学系统畸变误差源分解为加工误差、装调误差、工作温度变化引入的误差、以及调焦引入的误差4个主要部分,利用光学设计软件仿真分析了各误差源单独做用时对光学镜头畸变的影响情况,仿真结果表明在引入误差源的情况下,所分析的光学镜头的相对畸变不变,绝对畸变的最大变化范围小于2个像元尺寸,光学镜头的畸变稳定,有用于测绘相机的可能性。     

两相干点源对干涉仪测向系统干扰效果分析

干涉仪由于可实现单脉冲测向,具有良好的抗单点有源干扰能力,但可通过实施两点源相干干扰来干扰其测向性能。首先介绍两点源对干涉仪实施相干干扰的基本原理,并对干扰效果进行数字仿真,详细分析了影响干扰效果的相关因素,最后对实施两点源相干干扰的限制条件进行了说明。     

民用飞机进气道的侧风畸变研究

结合民用飞机动力装置/机体集成研究的具体需要,采用数值模拟方法对大涵道比涡扇发动机进气道的侧风畸变特性进行研究,给出了进气道在侧风条件下工作的流场特征,分析了导致侧风畸变的流动机理.研究结果表明:进气道的侧风畸变主要受到典型的气流分离与再附以及地面吸入涡等复杂流动现象的影响;当进气道内部气流出现分离时,侧风畸变会随侧风速度的增加而突然加剧;进气道在近地面工作状态,产生的地面吸入涡现象可能会使短舱的侧风容限明显降低.此外,侧风状态的进气畸变特性随着发动机流量的变化,进气道内部气流的分离与再附存在差别,这导致了进气畸变指数呈现迟滞变化.      

Aerodynamic performance enhancement of co-flow jet airfoil with simple high-lift device

The present study performed a numerical investigation to explore the performance enhancement of a co-flow jet (CFJ) airfoil with simple high-lift device configuration, with a specific goal to examine the feasibility and capability of the proposed configuration for low-speed take-off and landing. Computations have been accomplished by an in-house-programmed Reynolds-averaged Navier-Stokes solver enclosed by k-ω shear stress transport turbulence model. Three crucial geometric parameters, viz., injection slot location, suction slot location and its angle were selected for the sake of revealing their effects on aerodynamic lift, drag, power consumption and equivalent lift-to-drag ratio. Results show that using simple high-lift devices on CFJ airfoil can significantly augment the aerodynamic associated lift and efficiency which evidences the feasibility of CFJ for short take-off and landing with small angle of attack. The injection and suction slot locations are more influential with respect to the aerodynamic performance of CFJ airfoil compared with the suction slot angle. The injection location is preferable to be located in the downstream of the pressure suction peak on leading edge to reduce the power expenditure of the pumping system for a relative higher equivalent lift-to-drag ratio. Another concluded criterion is that the suction slot should be oriented on the trailing edge flap for achieving more aerodynamic gain, meanwhile, carefully selecting this location is crucial in determining the aerodynamic enhancement of CFJ airfoil with deflected flaps.     

真空低温环境用高精度CCD摄影测量系统

文章介绍了一套高精度CCD摄影测量系统,该系统是专门为在真空低温环境下的摄影测量而研制的,主要应用于卫星天线在模拟真空低温环境下的冷热变形测量试验。在试验过程中当卫星天线处于不同温度时,采用此系统对卫星天线表面进行高精度实时拍摄,将拍摄得到的数字图像传输给专门的图像处理软件分析,就能够得到卫星天线表面的变形数据。该系统的设计思想还可以扩展到其他小型设备在真空低温环境或其他特殊环境下的应用中。     

涡轮叶片尾缘扰流柱通道流动换热计算

为了深入研究涡轮叶片尾缘扰流柱区域流动的工程计算方法,用开发的基于流体网络计算的一维工程算法,对工作叶片尾缘扰流柱通道进行了计算,并与实验结果进行了对比。计算结果表明:工程计算得出的弦向出流量分布、压力分布从规律和数值上与实验结果都吻合较好,工程算法能够比较准确地计算出扰流柱通道的流动;扰流柱区的气体流动方向基本为弦向,但也存在着一定的径向流动,所以有必要在流体网络计算中设置表示径向流动的流路。     

复杂动态场景下目标检测与分割算法

在动态场景等复杂条件下,往往难以对序列图像目标进行准确的检测与分割。根据序列图像中目标在复杂条件下的成像特点,提出了一种基于融合尺度不变特征变换(SIFT)流特征显著模型的动态场景目标检测与分割算法。通过对SIFT流算法表示运动特征信息的优势进行分析,并结合图像国际照明协会(CIE)Lab颜色空间的颜色和亮度特征信息,建立四维特征向量空间。利用改进的多尺度中心-环绕对比方法生成各特征通道的显著图并进行线性融合,建立序列图像的动态场景目标显著模型。最后利用均值漂移聚类算法和形态学处理实现对检测目标的精确分割。实验结果表明,相比传统检测与分割算法,该算法在动态背景与航拍等复杂场景下能够分割出更为完整的目标区域,具有良好的鲁棒性和高分割精度。      

“交叉眼”干扰在单脉冲雷达中表现特征分析

“交叉眼”干扰技术被认为是最具发展前景的现代电子防卫手段之一。为开展其对抗技术研究,对单脉冲雷达在“交叉眼”干扰环境下的和、差接收信号进行了数学建模,并通过仿真计算分析了和、差接收信号所表现出的特征。初步分析结果表明：“交叉眼”干扰会导致单脉冲雷达差接收波束方向图发生畸变。畸变的严重性主要取决于干扰源和单脉冲雷达间的距离以及两干扰点源输出信号功率之比;“交叉眼”干扰同样会导致差、和接收信号功率之比出现异常。干扰源与单脉冲雷达间的距离越小和（或）“交叉眼”干扰的诱偏能力越强,差、和接收信号功率之比出现异常的角度范围越大。     

Research of multi-path routing based on network coding in space information networks

A multi-path routing algorithm based on network coding is proposed for combating long propagation delay and high bit error rate of space information networks. On the basis of traditional multi-path routing, the algorithm uses a random linear network coding strategy to code data pack- ets. Code number is determined by the next hop link status and the number of current received packets sent by the upstream node together. The algorithm improves retransmission and cache mechanisms through using redundancy caused by network coding. Meanwhile, the algorithm also adopts the flow distribution strategy based on time delay to balance network load. Simulation results show that the proposed routing algorithm can effectively improve packet delivery rate, reduce packet delay, and enhance network performance.