返回舱动稳定特性风洞试验的影响参数

再入飞行器需要大阻力减速而采取钝锥外形,这种气动布局外形的飞行器动稳定风洞试验结果易受到质心位置、尾迹干扰和极限环运动等因素的影响。通过风洞试验研究了不同质心位置、不同支撑方式下尾迹干扰对返回舱配平角和动稳定性的影响,以及不同稳定模态下,试验方法对试验结果的影响。指出了在动稳定风洞试验中必须精确模拟返回舱质心位置,在大攻角状态下采取弯支杆支撑方式减少尾迹干扰,并针对极限环运动,采取轴承一滑块大振幅自由振动试验,才能得到正确的返回舱动稳定特性。     

数字化车间异构设备数据源集成关键技术研究与应用

通过对异构设备工业网络环境下的统一数据接口技术、制造现场异构数据统一存储访问技术以及制造数据源可视化应用进行研究,结合金属件热加工车间异构设备的特点和具体需求,开展了C/S和B/S模式相结合的网络架构设计、数据源通道架构设计以及数据源实时性及有效性设计.对超塑成形设备、TAV气体扩散炉、热成形设备、热扭转设备、热校形设...     

VGA视频信号测量方法

本文论述了VGA视频信号一些重要参数的测量方法,提供了测试VGA视频信号的可操作手段.利用这些测量方法能够很方便地对VGA视频信号进行分析,有助于查找问题.     

动态异面压缩下铝蜂窝平均坍塌应力分析与试验验证

为研究铝蜂窝在动态异面压缩下的平均塑性坍塌应力，在铝蜂窝准静态压缩的理论研究基础上，考虑铝蜂窝应变率效应对材料力学性能的影响，采用Cowper Symonds模型，以基本折叠单元为研究对象，采用等效周长方法求取应变率，给出了两个动态异面压缩下铝蜂窝平均塑性坍塌应力的理论计算公式。落锤冲击试验结果与仿真结果显示，Tresca屈服准则下的动态平均塑性坍塌应力与试验及仿真结果的相关系数均在98%以上，验证了理论推导的正确性。本文给出的理论计算公式对研究动态冲击下铝蜂窝的异面压缩性能具有一定的工程指导意义。     

Evaluation of tensile properties of a compositemetal joint with a novel metal insert design by experimental and numerical methods

Composite-metal joints with a metal insert are one kind of connecting structure.In this paper,tensile experimental tests were carried out to investigate tensile properties of a composite metal joint with a novel metal insert design.Finite element models of the joint were established,and strain distribution and tensile strength were analyzed.The numerical results are in good agree ment with the experimental results.Results show that the joint failure is dominated by shear properties of the resin layer.Increasing the resin layer thickness in a certain range will improve the tensile strength of the joint,while increasing the radius of the fillet on the ending side of the metal insert will decrease the joint strength.Increasing the resin layer plasticity will improve the joint strength.The effect of the embedded depth of the metal insert can be ignored.     

一种用于高分辨扇扫成像的MIMO阵列

为了提高扇扫成像系统的方位分辨率,设计了一种具有高方位分辨率的多输入多输出(MIMO)阵列。首先,建立了同时适用于窄带和宽带信号的MIMO阵列与虚拟阵列之间的等效模型。在分析匹配滤波输出成分的基础上,证明了当发射信号具有良好相关特性时,MIMO阵列的匹配滤波输出可等效为单输入多输出(SIMO)阵列上经过脉冲压缩后的回波。接着,根据这一等效关系,获得了与MIMO阵列等效的虚拟阵列中虚拟发射阵元与虚拟接收阵元坐标解析解。最后,在约束阵列物理尺寸为固定值的前提下,利用该解析解设计出一种由2个发射阵元和一条接收均匀线阵列(ULA)组成的MIMO阵列。理论推导和仿真结果表明:所设计的MIMO阵列可以在恒定的物理尺寸和虚拟阵列为均匀直线阵的前提下,获得优于其他MIMO阵列和SIMO阵列的方位分辨率。     

Active flutter suppression of a multiple-actuated-wing wind tunnel model

In this study, a multi-input/multi-output（MIMO） time-delay feedback controller is designed to actively suppress the flutter instability of a multiple-actuated-wing（MAW） wind tunnel model in the low subsonic flow regime. The unsteady aerodynamic forces of the MAW model are computed based on the doublet-lattice method（DLM）. As the first attempt, the conventional linear quadratic-Gaussian（LQG） controller is designed to actively suppress the flutter of the MAW model. However, because of the time delay in the control loop, the wind tunnel tests illustrate that the LQG-controlled MAW model has no guaranteed stability margins. To compensate the time delay, hence, a time-delay filter, approximated via the first-order Pade approximation, is added to the LQG controller. Based on the time-delay feedback controller, a new digital control system is constructed by using a fixed-point and embedded digital signal processor（DSP） of high performance. Then, a number of wind tunnel tests are implemented based on the digital control system.The experimental results show that the present time-delay feedback controller can expand the flutter boundary of the MAW model and suppress the flutter instability of the open-loop aeroelastic system effectively.     

燃用重整气和煤油的燃烧室燃烧流场数值研究

为考察不同气液燃料对燃烧室性能的影响以及双燃料燃烧室设计时重整气显焓的影响,采用Fluent软件对双燃料燃烧室的燃烧流场进行了数值研究,并将重整气和煤油流场的计算结果进行了对比分析。数值模拟采用了Realizable k-ε湍流模型、PDF燃烧模型、离散相模型和SIMPLE算法。结果表明:燃烧室燃用不同气液燃料时,燃烧室内的回流区结构尺寸大体相同。当重整气和煤油的焓值相同时,重整气燃烧室内的最大轴向回流速度约为煤油燃烧室的5倍,温度降低约300K火焰变短,出口截面温度分布系数降低7.5%出口径向温度分布更均匀。进行气液燃料流量换算时,应考虑重整气显焓,否则会导致重整气燃烧室内的最大轴向回流速度增大约12%火焰拉长,燃烧室出口温度分布系数增大。     

基于变步长CFD/RBD方法的旋转弹轨迹仿真

采用变步长方法实现非定常Navier-Stokes方程和刚体六自由度运动方程的耦合求解,并对美国ARL旋转弹试验模型的飞行轨迹进行了仿真。旋转弹自由飞行过程中受到空气阻力作用,转速下降,气动力变化趋缓。因此轨迹仿真时先选取较小的时间步长,随着转速的下降逐渐增大步长,这样可以减少计算时间。刚体六自由度运动方程的数值求解采用变步长Adams预估校正法。将定步长和变步长两种方法应用于旋转弹实验模型轨迹仿真,并将计算得到的旋转弹空间位置、姿态角与试验结果进行了对比,结果显示:方法能较精确地仿真旋转弹飞行轨迹。在相同初始步长条件下,变步长方法较定步长方法计算时间减半;在相同计算时间条件下,变步长方法较定步长方法精度更高。     

Interaction of single-pulse laser energy with bow shock in hypersonic flow

Pressure sensing and schlieren imaging with high resolution and sensitivity are applied to the study of the interaction of single-pulse laser energy with bow shock at Mach 5. An Nd:YAG laser operated at 1.06 lm, 100 mJ pulse energy is used to break down the hypersonic flow in a shock tunnel. Three-dimensional Navier–Stokes equations are solved with an upwind scheme to simulate the interaction. The pressure at the stagnation point on the blunt body is measured and calculated to examine the pressure variation during the interaction. Schlieren imaging is used in conjunction with the calculated density gradients to examine the process of the interaction. The results show that the experimental pressure at the stagnation point on the blunt body and schlieren imaging fit well with the simulation. The pressure at the stagnation point on the blunt body will increase when the transmission shock approaches the blunt body and decrease with the formation of the rarefied wave. Bow shock is deformed during the interaction. Quasi-stationary waves are formed by high rate laser energy deposition to control the bow shock. The pressure and temperature at the stagnation point on the blunt body and the wave drag are reduced to 50%, 75% and 81% respectively according to the simulation. Schlieren imaging has provided important information for the investigation of the mechanism of the interaction.