无人水下航行器的发展现状与关键技术

无人水下航行器(Unmanned Underwater Vehicle,UUV)包括遥控水下航行器(Remotely Operated Vehicle,ROV)和自主水下航行器(Autonomous Underwater Vehicle,AUV),是海洋科学研究、资源开发和维护海洋权益不可或缺的重要装备,日益受到世界海洋国家的高度重视,并竞相大力发展。阐述了国外UUV的发展现状与应用情况,分析了AUV的关键技术及其发展趋势。     

单液滴羽状/液膜稀释破碎特性研究

为了获得气流中单液滴羽状/液膜稀释破碎特性,采用高速摄像机对液滴变形、破碎过程进行了捕获。实验结果表明:液滴的变形时间小于其破碎时间,且都随气动力增加呈负增长的变化趋势,其变化梯度、相同气动力下特征时间也都随液滴初始直径的增加而有所增加;液滴破碎区域面积随气动力增加呈先增加后减小再增加的变化趋势,且随液滴初始直径增加,液滴破碎区域面积也随之增加;破碎区域中子液滴质量百分数随气动力增加而增加,且随液滴初始直径增加而减小,其值变化的范围为0.48~0.66;液滴的破碎程度随气动力、液滴初始直径的增加而增加;破碎区域中子液滴细度与液滴初始细度的比值在0.18~0.23之间变化;在羽状/液膜稀释破碎阶段,多元线性回归理论可以用于建立子液滴数目、SMD的数学模型。     

旋翼桨尖涡生成及演化机理的高精度数值研究

为了细致捕捉直升机旋翼桨尖涡的生成和演化过程,建立了一个基于高精度网格和高阶通量计算格式的旋翼桨尖涡计算流体力学(CFD)求解方法。在该方法中,流场求解选取旋转坐标系下的Navier-Stokes方程为控制方程;空间离散采用迎风Roe格式,并采用低耗散的5阶WENO(Weighted Essentially Non-Osciltatory)格式进行对流通量的计算;时间推进则采用双时间法,在伪时间步上使用隐式LU-SGS(Lower-Upper Symmetric Gauss-Seidel)推进格式;应用嵌套网格方法实现桨叶网格和背景网格的数据交换。应用所建立的方法对悬停状态的旋翼桨尖涡流场进行了高精度模拟,在桨叶网格上精细地捕捉到了桨尖涡的具体生成过程,在背景网格上捕捉到了更多圈数的桨尖涡尾迹,并对桨尖涡的演化机理进行了深入研究。结果表明:建立的高精度数值方法能够有效地对旋翼桨尖涡的生成和演化过程进行细致模拟;悬停状态下旋翼桨尖气流在上下表面压力梯度的作用下经历了边界层增厚、逐渐卷起形成涡核以及最终脱离桨叶形成桨尖涡的过程。     

电网电压不平衡及谐波畸变时基波电压正负序分量分离新方法

针对传统锁相环(PLL)在电网电压不平衡及谐波畸变下利用常规软件锁相环不能准确获取相位的问题,提出了一种新的正负序分量分离新方法。利用了相序解耦谐振控制器能去除高次谐波和延时信号消除(DSC)法可滤除特定谐波的特性,将相序解耦谐振和延时信号消除法结合起来,达到更好的正负序分量分离的效果。最后,采用MATLAB/Simulink软件仿真结果证明了所提出方法的可行性和有效性。     

Aircraft nonlinear stability analysis and multidimensional stability region estimation under icing conditions

Icing is one of the crucial factors that could pose great threat to flight safety,and thus research on stability and stability region of aircraft safety under icing conditions is significant for control and flight.Nonlinear dynamical equations and models of aerodynamic coefficients of an air craft are set up in this paper to study the stability and stability region of the aircraft under an icing condition.Firstly,the equilibrium points of the iced aircraft system are calculated and analyzed based on the theory of differential equation stability.Secondly,according to the correlation theory about equilibrium points and the stability region,this paper estimates the multidimensional stability region of the aircraft,based on which the stability regions before and after icing are compared.Finally,the results are confirmed by the time history analysis.The results can give a reference for stability analysis and envelope protection of the nonlinear system of an iced aircraft.     

基于比例复数积分+重复控制的三相LC并网逆变器控制策略研究

针对传统PI控制的局限性,采用基于复数域的比例复数积分(PCI)控制与重复控制并联的新型控制策略,其中PCI控制可以在给定条件下消除交流稳态误差,重复控制能够抑制并网电流谐波,提高稳态控制精度。该新型控制策略可以较好地控制交流信号,能直接应用于三相abc坐标系,省去坐标变化环节,节约逆变器控制系统成本。最后通过MATLAB/Simulink仿真平台,建立LC型滤波器的逆变器并网模型,仿真分析证明了该控制策略的可行性。     

An experimental system for release simulation of internal stores in a supersonic wind tunnel

Aerodynamic parameters obtained from separation experiments of internal stores in a wind tunnel are significant in aircraft designs. Accurate wind tunnel tests can help to improve the release stability of the stores and in-flight safety of the aircrafts in supersonic environments.A simulative system for free drop experiments of internal stores based on a practical project is provided in this paper. The system contains a store release mechanism, a control system and an attitude measurement system. The release mechanism adopts a six-bar linkage driven by a cylinder, which ensures the release stability. The structure and initial aerodynamic parameters of the stores are also designed and adjusted. A high speed vision measurement system for high speed rolling targets is utilized to measure the pose parameters of the internal store models and an optimizing method for the coordinates of markers is presented based on a priori model. The experimental results show excellent repeatability of the system, and indicate that the position measurement precision is less than0.13 mm, and the attitude measurement precision for pitch and yaw angles is less than 0.126°, satisfying the requirements of practical wind tunnel tests. A separation experiment for the internal stores is also conducted in the FL-3 wind tunnel of China Aerodynamics Research Institute.     

进口总压不均匀性对燃气透平端壁气热特性影响的研究

为了研究非均匀进口总压引起的燃气透平内部流动特性变化对静、动叶端壁传热的影响机制,针对GE-E3透平第一级叶片在均匀、湍流边界层及航空发动机燃烧室出口实测得到的"C"型总压三种进口条件下进行了非定常数值计算。研究表明:非均匀进口总压相对均匀进口条件对静叶端壁附近流速和入口三角区传热产生了显著影响;湍流边界层总压相对均匀总压增强了前缘马蹄涡强度,从而使静、动叶端壁前缘传热系数分别增加100%和30%;"C"型总压使静叶端壁分离线下游和动叶端壁前缘局部传热系数降低;静叶内被湍流边界层总压增强的通道涡和由"C"型总压诱导产生的对转涡均会出现在动叶上下端壁附近;残余通道涡削弱了动叶端壁横向流动并使对应位置传热系数最大降低了12%,残余对转涡则增强了动叶端壁横向流动并使端壁传热系数最大增加了38%。     

阵风载荷减缓系统故障分析

阵风引起的额外载荷会引起飞机结构疲劳,降低结构使用寿命。采用非定常气动力有理函数拟合方法建立时域状态空间下的动力学系统,设计了阵风载荷减缓系统。研究了阵风载荷减缓系统3种典型故障模式(副翼偏转饱和、舵机卡死、副翼偏转延时)的力学建模方法,并对机翼在阵风减缓系统故障模式下的阵风响应进行分析。仿真结果表明,3种故障模式均不利于阵风载荷减缓系统对阵风载荷的减缓,对于一些特定情况,故障模式下的阵风载荷减缓系统不仅不能减缓阵风载荷,还会带来由副翼偏转不当引起的额外负载。     

基于线结构光的飞机蒙皮对缝阶差与间隙测量技术研究

针对飞机蒙皮对缝阶差与间隙的数字化检测问题,以线结构光视觉测量技术为基础,提出了阶差与间隙测量模型,从阶差与间隙的尺寸和位置两个方面设计测量方法。使用线结构光视觉传感器完成阶差与间隙的尺寸测量,同时利用iGPS测量系统对视觉传感器的位姿进行实时跟踪测量,从而确定阶差与间隙的测量位置。通过试验验证了算法的正确性和稳定性,能够实现非接触、高精度测量:试验结果表明:5mm内阶差的重复测量精度优于0.04mm,间隙的重复测量精度优于0.05mm。