涡轮叶片锥束体积CT检测系统软件原型

给出了检测系统软件原型的总体结构和数据流设计.研究了图像序列快速重建、高精度图像边缘检测、叶片点云模型与CAD设计模型配准、叶片壁厚检测与铸造缺陷分析等关键模块的实现方法.软件原型由C 6.0编程实现.仿真测试表明该软件可基于空心涡轮叶片的锥束体积CT扫描数据对叶片的外型轮廓偏差、壁厚和铸造缺陷进行检测分析.     

基于工业CT测量数据的空心涡轮叶片三维壁厚分析

航空发动机空心涡轮叶片的壁厚是保证叶片强度的一个非常重要的参数,需要生产阶段进行全面的检测.以涡轮叶片的锥束CT(computed tomography)图象序列和叶片CAD(computer aided design)模型为基础,给出一种基于模板的空心涡轮叶片三维法向壁厚自动分析方法.使用亚像素级边缘检测算法, 从叶片锥束CT图象序列提取叶片的高精度内、外表面点云数据,并进行空间栅格划分,以提高后续计算的效率.采用CAD驱动的模型配准方法实现叶片测量数据与CAD模型的可靠定位.依据叶片壁厚特征在叶片CAD模型上定义壁厚分析模板,通过壁厚分析模板与叶片点云数据的求交运算,得到对应区域的三维壁厚与壁厚偏差分布.使用一组仿真生成的叶片CT图象序列对三维壁厚计算精度进行验证.     

椭圆匹配法在空心涡轮叶片3D配准中的应用

在三维CT设备对空心涡轮叶片进行无损检测时会存在定位偏差问题 ,三维数字样品图像模型的配准是关键的一步。本文首先对CT切片图像提取轮廓点 ,然后借助转动惯量计算惯量椭圆并进一步对惯量椭圆匹配以获得所需的几何变换的参数 ,从而实现CT图像与理论模型之间的配准。仿真结果表明 :此方法用于空心涡轮叶片 3 D配准可取得满意效果     

基于中弧线的空心涡轮叶片壁厚计算方法研究

针对高精度复杂空心涡轮叶片壁厚测量问题,提出了一种基于中弧线的壁厚计算方法。通过对空心叶片CT切片数据的处理,建立了相应的点云数据测量模型,并与叶片CAD模型进行配准,实现了各截面数据点的提取与拟合,从而计算出了中弧线;在此基础上,运用UG二次开发平台求出了叶片各点的壁厚。实测结果表明:通过该方法能够精确计算复杂空心涡轮叶片的壁厚,提高空心叶片壁厚精度及其可靠性。     

钛铝合金涡轮转轴偏心问题的分析

对三体连接钛铝合金涡轮转轴偏心问题的产生原因、影响规律和检测方法进行了分析。三体连接钛铝合金涡轮转轴偏心问题产生的根源为铸造毛坯表面的第二次装夹,与首次加工和连接过程无关。偏心的直观现象是包容体周向壁厚不一致,会导致组件在较低的载荷下以拉脱的形式失效。采用超声测厚技术可以对钛铝合金涡轮转轴的偏心量进行无损检测。     

变壁厚涡轮冷却叶片参数化造型设计

提出了一种基于函数解析的变壁厚涡轮冷却叶片参数化设计方法。根据叶片外型线上定义的若干参数点,采用三次样条插值方法得到叶片壁面厚度分布函数,再通过计算得到冷却通道型线上离散数据点,在CAD平台下建立了变壁厚涡轮冷却叶片参数化模型。为实现涡轮冷却叶片的自动设计优化和多学科设计优化,获得更佳的叶片设计方案奠定了基础。     

轮廓度公差约束的叶片模型配准方法

针对公差非均匀分布的发动机叶片叶型检测评估问题,提出一种基于轮廓度公差约束的叶片模型配准方法。根据叶片轮廓度公差定义,给出一种基于中弧线的叶片轮廓度公差模型生成方法。建立了轮廓度公差约束的叶型截面配准数学模型,并给出了基于Nelder-Mead单纯形法的叶型截面带约束配准求解过程。采用仿真数据及实际叶片的三坐标测量数据与理论模型,对所讨论的模型配准方法进行了验证。结果表明,Nelder-Mead单纯型法可用于薄壁叶片模型的带约束配准求解;与最佳贴合配准相比,公差带约束配准方法可减少测量数据点集的超差点数目,为叶片检测评估提供更多参考。     

超超临界阀门超大壁厚壳体无损检测技术研究

针对超超临界阀门超大壁厚壳体的无损检测技术进行了探讨,主要对超声波检测、磁粉检测和渗透检测的适用范围和方法选择进行了分析,重点介绍了其中的超声波检测法,并结合大壁厚壳体的加工过程,对无损检测的检测时机做了探讨。     

基于图像的轮廓度测量与评定

针对微小型平面零件给出了一种基于图像的轮廓度测量与评定方法.包括实现轮廓度测量的理论轮廓数据建模方法、对应理论点的扩展极角定界搜索方法以及满足最小条件的最小极偏差轮廓度误差评定方法.通过实例将最小极偏差轮廓度评定方法(LDM)与传统的最小二乘轮廓度评定方法(LSM)进行了分析和比较.结果证明,对于不同实际零件,最小极偏差评定方法较最小二乘评定方法收敛于最小值的迭代次数减少了0～3次,精度优化了4%～12.6%,可以满足微型零件高精度、高效率轮廓度检测的要求.     

压气机叶片榫头轮廓数字化检测技术研究

基于三坐标测量机PC-DMIS软件测量系统和叶片UG模型,通过编制自动测量程序对叶片榫根的检测方法进行了研究,解决了使用传统投影法对榫根变公差轮廓度尺寸检测不精确和无法量化的问题和跨棒距数字化计算问题,同时采用自动化检测、批量矩阵式检测方式提高三坐标测量机在叶片检测中的效率。     

汽轮机叶片截型测量数据的自动分析

介绍了汽轮机叶片截型测量数据的分析处理方法,开发了叶片截型误差自动分析软件。对叶片截型测量数据的分析实例表明,该软件应用于叶片生产可获得满意的使用效果。     

Numerical predictions of roughness effects on the performance degradation of an axial-turbine stage

This paper describes a numerical investigation on the performance deteriorations of a low speed, single-stage axial turbine due to use of rough blades. Numerical calculations have been carried out with a commercial CFD code, CFX-Tascflow, by using a modified wall function to implement rough surfaces on the stator vane and rotor blade. To assess the stage performance variations corresponding to 5 equivalent sand-grain roughness heights from a transitionally rough regime to a fully rough regime, stage work coefficient and total to static efficiency were chosen. Numerical results showed that both work coefficient and stage efficiency reduced as roughness height increased. Higher surface roughness induced higher blade loading both on the stator and rotor which in turn resulted in higher deviation angles and corresponding work coefficient reductions. Although, deviation angle changes were small, a simple sensitivity analysis suggested that their contributions on work coefficient reductions were substantial. Higher profile loss coefficients were predicted by higher roughness heights, especially on the suction surface of the stator and rotor. Furthermore sensitivity analysis similar to the above, suggested that additional profile loss generations due to roughness were accountable for efficiency reductions.     

基于半马尔科夫决策过程的风力机状态维修优化

恶劣的工作环境、昂贵的维修成本和停机损失对风力机及其部件的维修提出挑战。以齿轮箱、叶片等风力机核心机械部件为对象,将部件退化过程离散成有限的退化状态;以长期折扣成本最低为目标,考虑风速、备件物流、停机损失等因素的影响,建立基于半马尔科夫决策过程的状态维修优化模型。分析各退化状态下的维修策略、检测间隔时间以及不同退化状态间的转移概率,并采用策略迭代算法求解模型。以某风力机齿轮箱为例,通过对等周期、非等周期检测条件下检测间隔时间和维修成本的分析,得到优化的维修决策。研究结果表明,该模型能有效描述风力机核心部件的退化过程,实现风力机维修优化。     

Surfacer二次开发在叶片锻件检测中的应用

简要介绍了逆向软件Surfacer的内外部开发模式,并利用其二次开发功能,结合叶片检测技术,研究开发了针对叶片锻件的检测系统.通过示例程序介绍了程序编写方法.经应用测试,系统可以顺利完成测量工作,界面简洁清晰,便于操作,与传统测量方法相比具有速度快、精度高等特点.该系统的应用对逆向软件在实际生产中的发展有着很大的推动作用.     

A study on an axial-type 2-D turbine blade shape for reducing the blade profile loss

Losses on the turbine consist of the mechanical loss, tip clearance loss, secondary flow loss and blade profile loss etc.,. More than 60 % of total losses on the turbine is generated by the two latter loss mechanisms. These losses are directly related with the reduction of turbine efficiency. In order to provide a new design methodology for reducing losses and increasing turbine efficiency, a two-dimensional axial-type turbine blade shape is modified by the optimization process with two-dimensional compressible flow analysis codes, which are validated by the experimental results on the VKI turbine blade. A turbine blade profile is selected at the mean radius of turbine rotor using on a heavy duty gas turbine, and optimized at the operating condition. Shape parameters, which are employed to change the blade shape, are applied as design variables in the optimization process. Aerodynamic, mechanical and geometric constraints are imposed to ensure that the optimized profile meets all engineering restrict conditions. The objective function is the pitchwise area averaged total pressure at the 30 % axial chord downstream from the trailing edge. 13 design variables are chosen for blade shape modification. A 10.8 % reduction of total pressure loss on the turbine rotor is achieved by this process, which is same as a more than 1 % total-to-total efficiency increase. The computed results are compared with those using 11 design variables, and show that optimized results depend heavily on the accuracy of blade design.     

Aerodynamic optimization of a high-expansion ratio organic radial-inflow turbine

Given that the radial-inflow turbine is a critical component of the Organic Rankine cycle system, its performance substantially influences system capacity. This paper established an optimization framework for the radial-inflow turbine is established with the combination of a computational fluid dynamics software, a non-uniform rational B-spline parameterization method, and an optimization strategy. The nozzle, meridional flow path, and blade profile of a 500 kW turbine were optimized. Results show that nozzle blade and impeller optimization leads to a 0.34 % and about 0.71 % increase in turbine efficiency, respectively. After optimization, the flow state in the turbine was good, and the flow separation almost disappeared.     

基于内流场分析的液力变矩器改型设计

为了提高液力变矩器的外特性,使其与发动机匹配良好,利用CFD软件对液力变矩器内流场进行三元流场数值计算和分析,在此基础上根据性能要求对原有变矩器作改型设计,改进了叶型进出口角、骨线形状和厚度分布等参数,以期得到分布合理的内流场,从而使改型后的变矩器具有符合要求的更优的外特性。改型后的液力变矩器具有更高的效率和与发动机匹配更优的泵轮容量系数,试验结果与计算结果非常吻合,改型设计效果良好。