控制力矩陀螺轴承组件摩擦力矩特性研究

控制力矩陀螺轴承组件是空间飞行器姿态控制系统的核心部件，其轴承的性能直接影响着空间飞行器姿态控制系统的控制精度和使用寿命，甚至危及空间飞行器安全.对于控制力矩陀螺轴承组件，轴承摩擦力矩大小及其波动性是轴承的关键性能指标，针对空间飞行器控制力矩陀螺轴承组件，在滚动轴承摩擦学和动力学基础上，建立六自由度控制力矩陀螺轴承组件非线性动力学微分方程组，并采用预估 校正的GSTIFF(Gear stiff)变步长积分算法进行求解，对其在有/无重力的工作环境、公 自转工况、轴承预紧力以及保持架兜孔间隙对轴承摩擦力矩幅值及其波动性的影响进行分析.分析结果表明：预紧力对轴承组件摩擦力矩影响显著，预紧力过大或过小都不利于降低摩擦力矩及其波动性，对于本文分析的轴承组件最佳预紧力为50~55N；保持架稳定性受重力影响显著，无重力时自转工况下保持架较稳定；过小的兜孔间隙会使摩擦力矩增大，过大的兜孔间隙会使摩擦力矩波动性增大，存在最优兜孔间隙使得摩擦力矩及其波动性都较小，针对本文分析型号的轴承组件，间隙比应控制在0.6~0.8之间.     

低轨天基信息定向分发区域分割编码控制方法

为提高低轨指向性信息分发链路的频谱利用效率，从天基分发平台与地面用户的相对位置关系入手，建立了分发指向、编码增益与信道传输容量的量化关系。在此基础上，提出一种低轨天基信息定向分发区域分割编码控制方法，该方法针对不同信息分发区域，采用最小均方误差(MMSE)作为区域分割准则选择编码方式，既提升了信道传输效率也便于工程实现。最后，本文通过仿真分析了方法的效能和性能影响因素，并与现有自适应编码方法进行了对比，验证了本方法的有效性和可靠性。     

Flow mechanism between purge flow and mainstream in different turbine rim seal configurations

The rim seal is used to prevent mainstream ingestion to the gap between the vane of a turbine and its blade. In this article, the dolphin lip with a hook configuration and a large seal cavity with hook structures are designed based on the high-pressure turbine datum single shark lip rim seal configuration. The sealing effect and parameters of the flow field are measured by an experiment method and a numerical simulation is used to explain the mechanism. For three configurations, the effect of the leakage slot vortex on the efficiency of the seal and the influence of leakage vortex, generated by the interaction between purge flow and mainstream flow, are discussed in depth. The result shows that the reverse vortex formed by the dolphin lip rim seal with hook structure will increase the sealing efficiency. The seal configuration with a large cavity improves sealing efficiency to a greater extent than the datum structure. At different purge flow rates and with unequal seal structures, the purge flow produces three types of leakage vortices in the passage. Besides, the seal configuration with dolphin lip produces a Kelvin-Helmholtz instability at the interface of the purge and the mainstream flows at a low purge flow rate to induce new leakage vortex branches in the passage of the blade.     

Aerodynamic performance enhancement for flapping airfoils by co-flow jet

Introducing active flow control into the design of flapping wing is an effective way to enhance its aerodynamic performance. In this paper, a novel active flow control technology called Co-Flow Jet (CFJ) is applied to flapping airfoils. The effect of CFJ on aerodynamic performance of flapping airfoils at low Reynolds number is numerically investigated using Unsteady Reynolds Averaged Navier-Stokes (URANS) simulation with Spalart-Allmaras (SA) turbulence model. Numerical methods are validated by a NACA6415-based CFJ airfoil case and a S809 pitching airfoil case. Then NACA6415 baseline airfoil and NACA6415-based CFJ airfoil with jet-off and jet-on are simulated in flapping motion, with Reynolds number 70,000 and reduced frequency 0.2. As a result, CFJ airfoils with jet-on generally have better lift and thrust characteristics than baseline airfoils and jet-off airfoil when C_μ is greater than 0.04, which results from the CFJ effect of reducing flow separation by injecting high-energy fluid into boundary layer. Besides, typical kinematic and geometric parameters, including the reduced frequency and the positions of the suction and injection slot, are systematically studied to figure out their influence on aerodynamic performance of the CFJ airfoil. And a variable C_μ jet control strategy is proposed to further improve effective propulsive efficiency. Compared with using constant C_μ, an increase of effective propulsive efficiency by 22.6% has been achieved by using prescribed variable C_μ for NACA6415-based CFJ airfoil at frequency 0.2. This study may provide some guidance to performance enhancement for Flapping wing Micro Air Vehicles (FMAV).     

基于改进粒子群优化模糊控制的MPPT算法研究

在光照强度和温度变化时,常规的最大功率点跟踪(MPPT)算法难以快速准确地跟踪光伏系统最大功率点。针对此问题,设计了一种改进粒子群优化算法(PSO)的模糊控制器。首先,依据常规MPPT特性,设计了一种带调整因子的模糊控制算法以快速收敛到最大功率点；然后,采用参数自适应PSO对设计的模糊控制器调整因子进行动态优化。仿真结果表明:所设计的参数自适应PSO优化模糊控制器能快速准确地跟踪最大功率点,保证了MPPT的动态响应速度和稳态精度,提高了光伏系统的工作效率。     

涡轮导向叶片综合冷却效率实验研究

为了研究流动参数对涡轮导向叶片综合冷却效率的影响,采用红外热像仪对叶片表面的温度分布进行了测量,得到了叶片的综合冷却效率随流量比、温比、主流进口雷诺数和湍流度的变化规律。实验过程中,次流与主流的流量比分别为0.15,0.18,0.20,0.22和0.24;主次流温比分别为1.4,1.7,1.93和2.2;主流进口雷诺数分别为1.0×10~5,1.1×10~5,1.2×10~5,1.3×10~5和1.4×10~5;主流进口湍流度分别为0.506%,8.156%,14.92%。结果表明,综合冷却效率在前缘处最低,沿流向逐渐升高;增大流量比会显著提高叶片的综合冷却效率,在温比为1.93时,流量比由0.15增大至0.24,综合冷却效率平均增加29.3%;温比和主流进口湍流度的增大均不利于综合冷却效率的提升,流量比为0.20时,温比由1.4增大至2.2,综合冷却效率平均下降46.5%,湍流度由0.506%增大至14.92%,综合冷却效率平均降低15.5%;主流进口雷诺数对叶片综合冷却效率的影响很小。     

机匣处理作用下高负荷轴流压气机转/静子匹配设计研究

为了探索机匣处理作用下转/静子的轴向匹配方法以进一步提高压气机级的失速裕度,研究了静子的叶型安装角及"弯"、"掠"规律对压气机性能的影响,针对机匣处理与优化静子的组合结构进行了非定常数值模拟,阐述了该结构的扩稳机理以及压气机新的失速机制。研究结果表明,在机匣处理作用下,静子成为压气机失速的触发因素,通过对静子叶型安装角及"弯"、"掠"规律的优化均可进一步提高压气机级的失速裕度,其中改变静子"弯"型对压气机级失速裕度的改善最大。组合应用机匣处理与尖部反弯根部正弯静子后,压气机效率基本不变,失速裕度提升了80.2%,较单独使用机匣处理提升30.9%。在该组合结构作用下,压气机的失速由静子触发,静子叶根吸力面在激波作用下发生附面层分离,且与轮毂表面附面层相互作用形成角区涡,接近失速边界时,静子叶根形成"前缘溢流,尾缘反流"现象,造成静子通道的大范围堵塞,诱发压气机失速。压气机级的扩稳应充分考虑机匣处理的影响,对静子进行优化设计。     

耦合热、动载荷的超超临界汽轮机迷宫密封动力特性

密封汽流激振严重影响超超临界汽轮机的安全运行,采用DEFINE_CG_MOTION和DEFINE_PROFILE控制宏建立转子的涡动方程,通过Workbench流固耦合方法计算热、动载荷下密封齿形变,根据快速傅里叶变化得到机组运行时的密封动力特性,并对转子稳定性进行分析。结果表明:蒸汽可导致密封齿膨胀变形,温度对密封齿长度变化影响可达1%~1.5%,压力和离心作用对其影响较小。热、动载荷使迷宫密封直接刚度减小,直接阻尼先增加后减小,交叉刚度先减小后增加,动力系数的最大变化为原来的2倍。35~55 Hz内转子稳定裕度急剧下降,转子对密封汽流激振更敏感。热、动载荷引起的压力波动集中在低频范围,密封周向压力波动可增高18.5 kPa。密封高压区的压力波幅剧增是汽流激振显著的主要原因。      

Distributed intelligent self-organized mission planning of multi-UAV for dynamic targets cooperative search-attack

This article studies the cooperative search-attack mission problem with dynamic targets and threats, and presents a Distributed Intelligent Self-Organized Mission Planning (DISOMP) algorithm for multiple Unmanned Aerial Vehicles (multi-UAV). The DISOMP algorithm can be divided into four modules: a search module designed based on the distributed Ant Colony Optimization (ACO) algorithm, an attack module designed based on the Parallel Approach (PA) scheme, a threat avoidance module designed based on the Dubins Curve (DC) and a communication module designed for information exchange among the multi-UAV system and the dynamic environment. A series of simulations of multi-UAV searching and attacking the moving targets are carried out, in which the search-attack mission completeness, execution efficiency and system suitability of the DISOMP algorithm are analyzed. The simulation results exhibit that the DISOMP algorithm based on online distributed down-top strategy is characterized by good flexibility, scalability and adaptability, in the dynamic targets searching and attacking problem.