隔离段内激波串受稳态和脉动背压影响的数值研究

本文基于非稳态雷诺平均的Navier-Stokes方程,探究在来流 条件下隔离段内激波串在稳态背压、脉动背压与隔离段自激振荡共振状态下的振荡特性。结果表明：隔离段激波串的自激振荡频率受稳态背压大小的影响,激波串在9倍和10倍来流静压的稳态背压条件下会产生频率分别为506Hz和454 Hz的自激振荡,且激波串前缘位置呈周期振荡。 在脉动背压条件下,激波串运动受脉动背压和自激振荡的共同作用,产生多个主导频率;当脉动背压振荡频率与自激振荡频率相近时,激波串运动达到共振状态,主要体现在激波串振幅的增强,振幅大小可以达到管道长度的33.5%,而受到100Hz的低频脉动背压影响时,振幅大小为管道长度的24%;同时共振状态下隔离段内上游的压升较受100Hz低频脉动背压影响的受迫振荡状态更高;出口脉动背压的相位变化对共振状态下激波串运动振幅几乎没有影响,表明激波串的自激振荡可能存在“自适应”特征,能匹配激波串受迫振荡的相位变化。     

风扇叶片叶尖扭转特性试验研究

为研究风扇叶片叶尖扭转特性,基于叶尖定时技术,建立一种发动机运行状态动态测量叶片叶尖弹性变形角的试验方法,在压气机试车台对小涵道比双级风扇试验件一级转子叶片不同工况下叶尖扭转特性开展了试验研究。试验结果表明：叶尖弹性变形角表现为随着转速升高而变大及随着特性线向失稳区移动而变大的特点,在100%换算转速近喘点达到本次试验风扇稳定工作状态的最大值1.25°。可变进口导叶（VIGV）角度仅在喘振边界附近对叶尖弹性变形角影响较大。在90% 转速、VIGV角度为-5°喘点处,叶尖弹性变形角出现大幅振荡,经估算,1号叶片喘振前扭转振幅为0.18°,喘点处扭转振幅为1.05°,退喘后扭转振幅为0.11°,通过监测弹性变形角测量叶片振动具有可行性。     

High-speed wind tunnel test of the CAE aerodynamic validation model

For the purpose of establishing and validating aerodynamic performance predictions at transonic Mach numbers, a wind tunnel test was conducted in the High-Speed Tunnel (HST) of the German-Dutch Wind Tunnels. The test article is the aerodynamic validation model from the Chinese Aeronautical Establishment, which is a full-span scale model representation of a business jet aircraft. The wind tunnel test comprised of parallel deployments of balance, pressures, infrared thermography, and model marker measurement techniques. Dedicated investigations with a dummy support were conducted as well, in order to derive and correct for the interference that the support system imposed on the overall model loads. This enabled the establishment of a comprehensive dataset in which the steady overall model loads, the wing load distribution, the state of the wing boundary layer, and the aeroelastic wing shape were quantified for conditions up to and beyond the cruise Mach number of 0.85.     

Delaunay graph-based moving mesh method with damping functions

The fluid–structure interaction and aerodynamic shape optimization usually involve the moving or deforming boundaries, thus the dynamic mesh techniques are the key techniques to cope with such deformation. A novel dynamic mesh method was developed based on the Delaunay graph in this paper. According to the Delaunay graph, the mesh points were divided into groups. In each group, a factor ranging from 0 to 1 was calculated based on the area/volume ratio. By introducing a proper function for this factor, this method can control the mesh quality with high efficiency. Several test cases were compared with other dynamic mesh methods regarding mesh quality and CPU time, such as radial basis function method and Delaunay graph mapping method.     

连接界面变形对转子动力特性影响的力学模型

针对航空发动机在工作过程中振动量增大且伴随有一定的界面磨损问题,在结构特征分析的基础上建立了三盘转子-支承系统动力学模型,并将接触端面同轴度偏差以及平行度偏差进行参数化描述,基于Lagrange方程得到考虑界面变形的高压刚性转子系统动力学微分方程。结果表明,界面变形将使得刚性转子系统产生附加激振力,同轴度偏差引起的附加激振力幅值与转速平方成正比,仅作用在相应自由度上;平行度偏差引起的附加激振力幅值仅与系统刚度和平行度偏差量有关,与转速无关,且其在支承自由度方向上存在一定分量。      

过冷大水滴变形与破碎的影响因素

过冷大水滴（SLD）结冰过程中,影响水滴变形与破碎及其导致的效应的因素众多,多种影响因素耦合作用于水滴变形与破碎的规律还未得到清晰认识。采用数值计算的手段,模拟了SLD运动过程中的变形与破碎现象,分别研究了水滴直径、流场速度及绕流物体尺寸变化对水滴破碎与变形及其效应的影响。通过研究,提出了包含SLD的典型流场区域划分方法,得到了不同因素对水滴破碎区域面积、物面的水滴收集特性、破碎子水滴分布特性的影响规律,发现水滴直径、流场速度、翼型前缘半径与变形和破碎影响撞击特性的程度呈正相关关系。在此基础上,提出了一个综合影响参数X,线性回归分析的结果初步说明,X是表征水滴变形与破碎及其效应的合适参数。相关工作可以为SLD结冰的计算、试验以及防/除冰设计提供参考。     

Whole-process modeling of titanium disc forming for gradient distributions of temperature and deformation

Gradient distributions of temperature and deformation (GDTD) are crucial for achieving dual-performance discs of titanium alloys which is required by the service environment of aeroengine. However, heating, cooling and deforming sequence in the whole process of the titanium disc forming, which leads to difficulties for achieving GDTD due to a lot of parameters. To solve this problem, a whole-process model of the titanium disc forming for GDTD has been established. In the model, heating and cooling via heat radiation, conduction and convection, and deforming by local loading with mold chilling are all considered. Experiments on heating and cooling as well as deforming were carried out by using a furnace and the Gleeble-3500 machine. The experimental data are used to determine thermal parameters and constitutive relations of the IMI834 titanium alloy, and then to verify the reliability of the model. Then the model was used to simulate the evolution rules of temperature and deformation of the titanium disc. The results show that the heating surface, furnace temperature, billet profile and loading rate play the core role for the control of GDTD, and thus a set of parameters were determined. Therefore, this work provides a base for developing a new forming technology of the dual-performance titanium discs with the approach of local heating and local loading.     

钉孔挤压强化弹塑性计算中形变理论适用性探讨

本文为了检验形变理论在计算钉孔挤压残余应力场的可用性,对同一模型分别釆用全量法和增量法进行有限元计算,计算结果表明:在小的挤压量下,即δ≤2％(挤压量δ定义为(D_棒-D_板)/D_板×100％),两种方法均可釆用,当挤压量较大,即δ>2％时,全量法的结果与边界条件吻合得不好,而增量法符合得很好。从实验结果看,用全量法计算的残余应力计算试件的疲劳裂纹起始寿命与实验结果相差较大,而增量法计算的该寿命则与实验结果接近。工程中的挤压过程大都釆用较大的挤压量,所以,形变理论不适合计算钉孔挤压的残余应力场。     

用于导弹发射装置的平衡机

简述了导弹发射装置中弹簧式和扭杆式两种平衡机的特点及制造工艺。介绍了单发、多联装、箱式和舰用型等不同导弹发射装置中平衡机的结构布局,以及各自的特点,给出了平衡机设计的一般原则。     

超空泡水下航行体的结构动力响应特性

通过综合有关文献的理论,得到作用于超空泡水下航行体尾部的冲击载荷与航行速度的关系,然后利用有限元法研究了在不同速度条件下航行体的结构动力响应和变形特性.得到了加速度响应的主频率及其取值区间、航行体内的最大应变值及其分布位置;并给出了加速度响应主频率以及航行体内最大应变值与运动速度的关系.计算结果表明:存在2个加速度响应主频率,当航行体航速相对较低时,应采用第1个主频率作为结构设计时的参考频率,速度较高时应采用第2个主频率;计算还表明:航行体内最大应变值随着航速的增加而显著增加.结果对超空泡水下航行体的结构强度分析和结构优化设计有着指导意义.