涡轮静叶表面全气膜冷却效率实验研究

采用放大的涡轮静叶模型,利用大尺度低速线性叶栅风洞进行实验,测量了涡轮导向叶片表面完全气膜覆盖情况下气膜冷却特性。风洞实验段由三个叶片组成,中间叶片为实验叶片,由有机玻璃制成。叶片表面共有54排孔,前缘8排,压力面21排,吸力面25排。对叶片前腔和后腔表面的换热情况分别进行实验,主要研究了不同主流雷诺数及不同质流比对气膜冷却效率的影响。研究结果表明：气膜对前腔壁面冷却效果总体上优于后腔壁面,在叶片不同区域气膜冷却效率随质流比和主流雷诺数的变化规律有所不同。     

涡轮导向器叶片喉道面积值的三坐标测量

讲述涡轮导向器叶片组件喉道面积值作为航空发动机设计和生产中的重要参数,如何加以严格的控制。其中以某涡扇发动机高压涡轮导向器叶片组件为例,对用三坐标测量涡轮导向器叶片组件喉道面积的优越性、测量原理、测量方法及测量过程的控制进行详细阐述。     

双目立体显微测量的研究

双目立体视觉是计算机视觉的一个重要分支,即由构成一定角度的两台摄象机拍摄同一幅画面,通过计算空间点在两幅图像中的视差,获得该点的三维坐标值.提出将双目立体计算机视觉技术应用于光学立体显微镜上,可对一些微小物体进行观测和测量,并获取深度信息,建立三维图象,从而用简便、经济的手段进行微小物体的三坐标测量.     

基于单目视觉系统的三维重建方法

以单相机采集的单幅彩色图像为基础,提出了基于单目视觉系统的表面三维形貌重建方法.该方法采用课题组针对该问题设计的多色LED环形结构光源,通过标定光源内各色LED的安装高度、入射角度、分布密度,使采集到的彩色图像包含入射光的位置信息.基于视觉系统中提取的入射光信息、图像色彩信息、相机成像模型和图像的灰度信息,建立了三维重建模型,提出了面向微小器件的表面三维重建方法.该方法解决了传统SFS法反向重建表面形貌的不确定性和慢收敛性问题.实验研究结果表明:采用本文所提方法重建圆形垫圈和六角棱柱型螺母,其重建相对误差分别为-2.2%和-4.43%,证实了采用单相机结合环形光源重建微小物体的表面三维形貌是有效的.     

建立叶片气膜孔工件坐标系的方法研究

建立叶片气膜孔工件坐标系是测量气膜孔直径和坐标位置的基础,它一直是几何量检测技术领域的难题,本文简要介绍了一种方便快捷的叶片气膜孔工件坐标系的建立方法,对解决叶片气膜孔测量难题具有一定参考价值.     

极线约束法在微波天线三维视觉测量点匹配中的应用

在三维视觉测量中,通常需从2幅或多幅图像中获取物体的三维信息.必须找出与同一物点相对应的多幅图像中的对应像点,这一过程叫图像点匹配.图像点匹配技术是三维视觉测量技术走向自动化的关键技术之一.论文叙述了图像点匹配的极线约束法原理及针对实际问题的解决方案.本文给出了极线约束法在微波天线三维视觉测量图像点匹配中应用的实验结果,表明该方法可行,具有实用价值.     

基于相位法的三维面型测量及曲面重建技术

文中采用相位法对三维面型测量和曲面重建技术进行了探讨,实现了三维信息获取和曲面重建的方法。该方法是用非相干光源投射的虚拟光栅和 CCD 摄像机构成的视觉系统对物体进行一次扫描获取物体表面的三维测量数据,这些数据经过处理后转换成*.ibl 文件,借助于 Pro/Engineer 软件重建三维物体表面。该方法快速、简便,适合于实时测量、加工,同时可实现测量、处理、加工的一体化,从而为反求工程的发展提供了一个很好的新方法。最后给出了实验,实验结果证明了方法的可行性和有效性。     

基于阈值增量的动态眩光测量方法

通过分析阈值增量的评价标准得到影响其变化的基础分量为亮度信息和位置信息,提出了一种基于阈值增量的动态眩光测量方法,建立了实验测量系统.该系统利用图像采集器获取环境图像信息,通过图像亮度标定与双目摄像机的视觉特性分别获取图像亮度信息和三维坐标信息,实现对单帧图像阈值增量的计算,最后依据系统运算时间估算出系统的检测频率,并...     

基于RGB-D值的三维图像重建系统研究

针对目前视频画面角度固定、缺乏深度和人机互动的问题,本文利用Microsoft Kinect体感摄像机可以同时获得彩色图像和深度图像的特点,搭建了基于多台Kinect的三维图像重建系统,实现了在DepthOfField10.1环境中可以手动旋转,看到不同视角的三维图像.本系统首先通过校准得到相机标定参数,然后将获取的彩色图像和深度图像进行自身数据融合生成一组三维点云数据,同时通过坐标转换将三维数据在世界坐标系中表示,再将多组点云数据进行融合重建,在进行重建的过程中运用纹理贴图技术进行渲染,得到3D图像.由此得到的立体图像可以通过旋转看到各个角度的三维图像,具有很强的立体感.通过对系统的初步实验验证了本系统的可行性.实验结果表明:本系统可以实现手动旋转三维图像,获取不同角度的三维画面,增强人机互动.     

基于面结构光的叶片三维重构技术研究

为提高叶片三维检测速度与相位解码过程中的准确性等,通过选择投射解码准确率高的格雷码编码策略的结构光,同时避免叶片表面涂显影剂与粘贴标定点的方法,进行基于面结构光的叶片三维重建技术研究。通过选择合理的实验设备,设计机械结构,搭建一种基于面结构光的三维视觉检测实验系统。对三维视觉检测实验系统的标定方法与重构算法进行理论研究,利用三维视觉检测实验系统完成叶片某一位置的三维重构实验,并获得叶片的离散点云数据;试验结果进一步论证所设计系统的可行性,可为后续叶片三维视觉检测实验系统的研究提供基础。     

An equivalent model for mechanical analysis of single crystal cooled blade with film cooling holes using crystal plasticity

Modern cooled turbine blades made of single crystal superalloy contain lots of film cooling holes. It is difficult to simulate the mechanical behavior of the blade as so many holes. Developing precise equivalent model is an effective method to solve this problem. In this work, an equivalent model based on crystallographic theory has been presented to deal with film cooling holes. A unit cell model with film cooling hole and an equivalent model without cooling hole are established to determine the equivalent parameters first. And then the flat specimen made of single crystal with 14 holes is designed to verify the feasibility of the equivalent method. The tensile test and finite element simulation are carried out to study the load-displacement curve of specimen. The experimental results and fracture surface of specimens show that the equivalent method based on local failure is reasonable. The method is a useful way to analyze the mechanical behavior of cooled blade with film cooling holes and to avoid the fracture of the cooled blade.     

Surface Degradation and Cracking in Combustion Turbine Blade Cooling Passages

The depth of internal oxidation and nitridation from the surface of the 16 cooling holes in a first-stage turbine blade was measured by optical microscopy after 32,000 hours of service. Maximum depth of penetration was 15.5 mils (0.4 mm) at the trailing edge hole. An effort was made to predict hole surface metal temperatures based on these measurements using the Arrhenius relationship between time and temperature with depth of oxidation assumed to be parabolic with time. Good correlations were obtained between the finite element analysis results and the predictions. In the thickest part of the airfoil, where metal temperature is minimum, intergranular cracks up to 1.2.6 mils (0.32 mm∥ in depth were found at the surface of the cooling holes. Measurable attack was only one to two mils (0.025-0.050 mm). Based on an approximate elastic-relaxation-local inelastic stress analysis, it was calculated that inelastic local strains of over one percent occur at the points of cracking. No cracking was observed in the hotter holes, but cracking did occur in a trailing edge tip cooling hole when weld repair of the tip squealer was attempted indicating that embrittlement had occurred from the environmental attack.     

Investigation on crystallographic behaviors of nickel‐base single crystal alloy cooling holes with different spanwise injection angles

Film cooling as an important thermal protection technology is widely used in aviation and ground gas turbine blades. But film cooling holes reduce the strength of blade seriously, which have become a key region of crack nucleation. In this paper, the plastic behaviors of nickel‐base single crystal alloy turbine cooling holes in spanwise injection angles range from 0° to 40° are investigated on basis of crystallographic constitutive theory. The results show that there are both higher stress regions and lower stress regions around multi‐column cooling holes, where suffer stress interference. The maximum Mises stress occurs at the hole in the center column. The places where the maximum resolved shear stresses occurs change with load and spanwise injection angle. The maximum Mises stress around holes with injection angle of 0° is lowest. With the injection angle increases, the maximum Mises stress increases until injection angles up to 30°. In all the slip systems, the resolved shear stress of hexahedral slip system is most sensitive to the changing of spanwise injection angle and load.     

Analysis of surface quality of multi-film cooling holes in nickel-based single crystal superalloy

The effect of the surface quality of multi-film cooling holes processed by laser drilling (LD) and electrical discharge machining (EDM) on the mechanical properties of blades have been studied. The physical features of the cooling holes, including the diameter, conicity and shape of the holes, are measured by optical microscopy, demonstrating that the EDM process is not as accurate as the LD process. Meanwhile, metallurgical characteristics, including the recast layer, heat affected zone and micro-cracking within the surface layer, are analysed by scanning electron microscopy, demonstrating that the radial crack generated in the LD process is more dangerous than the circumferential cracks generated in the EDM process. Using finite element analysis (FEA), the single crystal superalloy specimens with multi-film holes are simulated based on the crystal plasticity theory, showing that a significant increase of the stress gradient is observed in a real hole model than in an ideal circular hole model, which means that a shape simplification in the blade design will reduce the reliability of the blade. Based on the findings above, the influence of the surface quality of holes is investigated to obtain the possible damages to nickel single crystal turbine blades.     

Aerothermal shape optimization for a double row of discrete film cooling holes on the suction surface of a turbine vane

A multiple-objective optimization is implemented for a double row of staggered film holes on the suction surface of a turbine vane. The optimization aims to maximize the film cooling performance, which is assessed using the cooling effectiveness, while minimizing the corresponding aerodynamic loss, which is measured with a mass-averaged total pressure coefficient. Three geometric variables defining the hole shape are optimized: the conical expansion angle, compound angle and length to diameter ratio of the non-diffused portion of the hole. The optimization employs a non-dominated sorting genetic algorithm coupled with an artificial neural network to generate the Pareto front. Reynolds-averaged Navier–Stokes simulations are employed to construct the neural network and investigate the aerodynamic and thermal optimum solutions. The optimum designs exhibit improved performance in comparison to the reference design. The optimization methodology allowed investigation into the impact of varying the geometric variables on the cooling effectiveness and the aerodynamic loss.     

基于线结构光的叶片型面特征检测方法研究

叶片是燃气轮机和航空发动机的核心部件,随着我国两机行业的高速发展,对于叶片在研发、生产和维修等方面全生命周期检测的要求不断提高。光学测量是目前叶片三维形貌高效检测的新手段,但是在测量精度等方面相比传统三坐标测量机仍存在一定局限。该文提出一种基于线结构光的叶片型面特征检测方法,设计开发一套四自由度检测平台,针对基于标定物的平台位姿校准和数据采集方法开展研究,并以某气轮机导向叶片为检测对象进行实验测试。测试数据与精密三坐标测量机实测数据的对比结果表明:型面型线轮廓度偏差在±0.02 mm以内,截面主要特征参数偏差均在±0.018 mm以内,该文面向叶片型面实际检测需求的方法可行。     

5号汽轮机叶片断裂原因分析

对某热电厂5号汽轮机的断裂叶片进行了宏观形貌、化学成分、金相组织以及扫描电镜形貌和元素成分能谱分析。结果表明,叶片失效性质为腐蚀疲劳断裂;叶片拉筋孔处的点蚀坑是裂纹源;造成叶片发生点蚀的原因是蒸汽中含有的氯、硫等介质。     

Local investigation of the optical properties of subwavelength rectangular holes with a focused beam of electrons

The optical properties of rectangular subwavelength holes in a gold film are investigated using the light generated when a focused beam of electrons impinges on the sample close to the hole. Using this technique, multi-spectral maps of the holes are obtained with a resolution beyond the optical diffraction limit. The results show the influence of hole shape on the spectrum of locally scattered light. Rectangular holes of varying shape and size are investigated, and the spatial distribution of the polarization of the observed light is measured. The influence of neighbouring holes is investigated by measuring small clusters of holes.     

镍基单晶合金涡轮叶片开裂原因

某发动机高压涡轮叶片为镍基单晶合金叶片,在室温下进行振动疲劳试验后发现叶片开裂,通过宏观观察、金相检验和扫描电镜分析等方法对叶片开裂的原因进行了分析.结果表明:进气边叶根和榫头伸根的开裂形式均为疲劳开裂;进气边叶根气膜孔内壁存在多处小缺口及榫头伸根亚表面存在疏松缺陷,这些缺陷部位容易形成裂纹源,促进了裂纹的萌生,裂纹扩...     

发动机叶片型面测量坐标系建立方法研究

发动机叶片的复杂外形结构和加工误差给叶片形位尺寸的精确高效测量带来很大困难.利用三坐标测量机对叶片的型面参数进行测量时,对于变形较大无法利用设计基准完成测量的截面,通过建立辅助测量坐标系的方法实现扫描.本文分析了建立辅助测量坐标系的原理,并提出一种利用四点拟合快速建立辅助坐标系的算法,将变形大的实测曲线与理论叶型进行迭...