总压畸变对超声速压气机动叶端区流场结构的影响

采用全周非定常数值模拟方法,对两种畸变进口条件下的超声速压气机流场进行求解,了解动叶流场参数变化和气动性能与畸变来流条件的关系,重点分析动叶根部和顶部附近激波位置、结构和强度的变化情况,揭示动叶流场参数的动态变化规律.研究表明,随畸变区范围增加,压气机质量流量和效率下降;动叶流场参数对畸变来流的动态响应主要表现为激波位置、结构和强度的周期变化,当畸变区范围足够大时,流道在畸变区中会经历深度畸变;27.2％畸变时,畸变区内流道存在根部和顶部流动状态不一致的时刻,流场状态复杂.38.2％畸变时,畸变区内动叶叶顶和叶根区域都能达到深度畸变状态,流动损失较大且稳定性差.     

灵巧型大孔径四反星敏感器镜头设计

星敏感器镜头是星敏感器姿态轨道控制系统的重要组成部分，具有相对孔径大、工作谱段宽、绝对畸变低的特点，针对这些特点，在四反射镜初始结构的基础上，分析了镜头探测能力和相对孔径的关系，明确了镜头设计指标，利用非球面反射镜强大的像差校正能力，优化设计得到了全反射4反星敏感器镜头。镜头焦距170mm，轴向长度50mm，镜头F数2，等效入瞳直径51.2mm，圆视场±2.25°。镜头工作波段可由膜系决定，无色差，空间频率35lp/mm处传递函数优于0.6，畸变优于0.01%，弥散斑直径优于13μm，系统15μm范围内能量集中度优于80%，渐晕系数小于0.95，该镜头可用于亚像素精度的飞船姿态轨道控制系统，为星敏感器导航光学系统设计提供了参考。     

扩压式双S隐身进气道设计和流场分析

采用扩压式双S隐身进气道能够提高飞行器的隐身特性和综合性能。针对保形短程、高隐身、大偏距的亚音速隐身无人机进气道,以保形入口、中间控制面和出口截面为约束并结合多项式对中心线和面积、截面形状进行控制,实现对保形进口截面形状和弯曲形式复杂的双S隐身进气道的快速设计;在此基础上,研究中心线曲率、面积分布和中间截面形状等参数对进气道性能的影响。结果表明:双S进气道流场特性复杂,第二S弯处顶部的分离和空间二次涡引发的流场畸变的综合控制是设计的重点,通过截面参数约束并结合多项式能够对双S进气道内的流场品质进行控制;在中心线曲率、扩张角和多项式参数等配制上应该朝利于第二S弯流场稳定的方向靠近。     

飞机进气道/ 发动机台架联合试验及匹配特性研究

为了确定发动机地面装机条件下的进气畸变大小,对1种全尺寸进气道与发动机地面台架开展进发联合试验研究。试验速度条件为飞机静止状态,对应飞机迎角为0°,马赫数为0。参试进气道为2元外压式超声速进气道,参试发动机为大推力双转子带加力涡轮风扇发动机。采用地面台架联合试车的方法,获得了不同进气道条件下的进发匹配特性数据,包括在发动机不同工作转速下进气道出口流场的稳态总压特性、动态畸变特性等参数,并与进气道缩比模型风洞试验结果进行了对比分析。结果表明:全尺寸进气道的出口畸变随发动机空气流量增加而增大,与风洞试验结果一致,但防护网对于畸变的影响效果相反。     

一种瞬时大带宽DRFM系统的信道化设计

为实现宽带雷达回波信号的模拟生成,通常采用基于信道化技术的射频存储(DRFM)系统。在信道化DRFM系统中,不合理的信道划分方案和多相滤波器设计会导致频谱混叠、频谱分量缺失和幅度失真。文章提出了一种相邻信道频谱有50%交叠的信道划分方法,并对信道化滤波器组进行了优化设计。在此基础上,给出了一种瞬时大带宽DRFM系统的实现方案。仿真结果表明,文章提出的设计方案可以实现Nyquist采样带宽内雷达信号的射频存储和模拟转发,且具有较小的幅度失真,可以满足瞬时大带宽雷达回波信号的模拟需求。     

A refined design method for precoolers with consideration of multi-parameter variations based on low-dimensional analysis

The precooler is a distinctive component of precooled air-breathing engines but constitutes a challenge to conventional thermal design methods. The latter are based upon assumptions that often reveal to be limited for precooler design. In this paper, a refined design method considering the variations of fluid thermophysical properties, flow area and thermal parameters distortion,was proposed to remediate their limitations. Firstly, the precooler was discretized into a fixed number of sub-microtu...     

Adaptive feedback control of stability in an axial compressor with circumferential inlet distortion

The adaptive feedback control of stability with circumferential inlet distortion has been experimentally investigated in a low-speed, axial compressor. The flat-baffles with different span heights are used to simulate different distorted inflow cases. Compared with auto-correlation and root-mean-square analysis, cross-correlation analysis used to predict early stall warning does not depend on the distortion position. Hence, the cross-correlation coefficient was used to monitor the stable status of the compressor and provide the feedback signal in the active control strategy when suffering from different distortions. Based on the stall margin improvement of tip air injection obtained under different distorted inflow cases and the sensitivity analysis of cross-correlation coefficients to injected momentum ratios, tip air injection was adopted as the actuator for adaptive feedback control. The digital signal processing controller was designed and applied to achieve adaptive feedback control in distorted inflow conditions. The results show that the adaptive feedback control of air injection nearly achieves the same stall margin improvement as steady air injection under different distortion intensities with a reduced injection mass flow. Thus, the proposed adaptive feedback control method is ideal for the engine operation with circumferential distorted inflow, which frequently occurs in flight.     

插板进气畸变与压气机的耦合数值模拟

为了探索进气道/发动机一体化设计方法,发展了一种压气机与进气畸变耦合计算的方法.首先从压气机基准流场雷诺平均Navier-Stokes(RANS)仿真结果中提取压气机叶片对气流的作用力,建立压气机全通道体积力模型.再将压气机体积力模型加入到流体计算软件CFX中,实现插板进气畸变与压气机的耦合计算.与实验结果对比表明:压气机体积力模型能有效模拟压气机与上游畸变流场的耦合作用,相比传统的全通道RANS计算能减少近2个数量级的计算网格数.