现代汽轮机叶片型面制造技术

介绍当今世界汽轮机叶片型面制造最新设备——NX系列五坐标数控型面机床及其工艺特点，概述数控程序设计软件RCS的应用，针对本公司产品，通过实践，总结叶片型面制造经验。此加工方式是国内今后汽轮机叶片制造的发展趋势。     

汽轮机叶片虚拟制造仿真研究

文章通过VERICUT平台,定制开发汽轮机叶片虚拟仿真控制系统,实现汽轮机叶片虚拟制造仿真.该仿真控制系统可提高汽轮机叶片数控加工程序的安全性、产品质量、制造系统的工作效率和数字化车间基础数据的准确性.     

300MW钛合金动叶片型面加工工艺分析

根据300MW机组低压次末级钛合金动叶片的特点,利用Master CAM、Pro/E和RCS联合造型,并针对五坐标机床特点,利用RCSSOFTWARE编制出合理高效的数控加工程序。     

汽轮机叶片的建模及插补算法研究

为提高汽轮机的工作效率,汽轮机叶片的表面通常是设计成扭曲的变截面曲面,叶片形状十分复杂,因此,汽轮机叶片的精确几何造型对保证叶片加工质量十分重要。进行汽轮机叶片数学建模和数控插补算法研究,根据图纸数据对汽轮机叶片进行基于NURBS曲线和曲面的反求计算,建立了汽轮机叶片的精确数学模型。针对叶片高速高精度数控加工的要求,以叶片数学模型为基础,建立叶片截面的NURBS曲线组,利用MATLAB编程仿真,验证了采用不同插补算法进行叶片数控加工的适应性。     

汽轮机叶片数控加工刀位轨迹的计算

为了提高汽轮机叶片数控加工的质量和效率,用2×3次非均匀有理B样条方法,建立复杂叶片的数学模型,实现了叶片的数字化表示。针对叶片横截面曲率变化大的特点,采用等参数和等弦高相结合的方法计算走刀步长,利用等残留高度法确定行距,仿真实例表明,生成的刀具轨迹能提高叶片加工精度和加工效率。     

叶片型面数控砂带磨削的后置处理

论述了叶片型面五坐标联动计算机数控砂带磨削的软件插补和恒速控制方法,推导了刀位数据到机床五坐标的几何转换关系和刀具与工件碰撞的判别式,并指这种机床结构中的工件转动坐标既是插补过程中的联动坐标,又是工艺过程中的铺助坐标。为减少插补误差、满足加工精度要求,引入粗插补和精插补的概念。文中结合扭叶片加工示例进行了分析。     

数控加工在叶片叶身型面加工中的应用

叶片叶身型面是叶片零件的主要特征表面。叶身型面加工，难度大、工作量大、在整个叶片生产过程中，占有重要的地位。本文通过叙述数控加工在叶片叶身型面加工中的应用，探讨如何充分发挥数控机床的作用，以及分析叶片数控加工机床选用应考虑的原则。     

棕树型叶片汽道型线的数控加工

叶片是汽轮机的主要部件之一,尤其它的汽道部分决定了汽轮机的发电功率,直接影响到汽轮机产品的质量,也直接影响叶片的工作效果,进而直接影响整机的工作性能,叶片汽道型线部分是复杂空间三坐标数据点,加工精度要求很高,加工难度很大.本文通过对叶片的造型及数控编程,使大家对叶片类零件的数控加工过程有一个整体的了解.     

二三维一体化中叶片型线自动化处理的基本原理及其实现方法

对采用VL、UG/Open进行基于AutoCAD、UG的应用程序二次开发进行了研究,提出了叶片型线自动化处理的基本原理及其实现方法。该方法为进一步叶片参数化建模、CMM三坐标测量机的检测分析及数控加工奠定了基础,对于开发复杂的参数化设计系统具有一定的参考价值。     

基于Pro/E的汽轮机叶片造型及数控编程研究

以典型的CAD/CAM软件Pro/Engineer Widefire2.0中文版为基础,用曲面混合的参数化建模方法建立了汽轮机叶片的三维实体模型,并用B样条曲线对其进行了光顺处理;在CAD模型的基础上,分析了叶片的加工工艺流程,并用软件的CAM功能对叶片进行了数控加工仿真,生成了Nc代码.     

船用燃气轮机变几何动力涡轮大攻角流动特性的三维数值模拟

采用三维数值模拟技术，研究了可调导叶转动导致变几何动力涡轮气动性能变化的流场机理。结果表明，在较小的转角范围内，采用大转折角设计的可调导叶使涡轮处于大攻角运行。在大正攻角或大负攻角下可调导叶级动叶栅流道内的三维分离流场结构及其产生机理有很大差异，而且大正攻角造成的吸力面分离流动更使整个涡轮的效率显著地下降。通过系统的机理分析，提出可调导叶宜采用较小转折角的后部加载叶型，而变几何动力涡轮可调导叶级动叶栅要采用较大负冲角的气动设计原则。     

基于离散数据的汽轮机叶片荒加工的研究

汽轮机叶片毛坯在铸造过程中变形严重,导致粗加工时余量分布极不均匀,提出了一种新的毛坯荒加工算法.该算法能直接从测量数据中生成荒加工刀位轨迹.首先将待加工曲面按照参数线进行网格划分成曲面片,然后采用投影的方法确定每个网格内的曲面片是否为可加工,并将这些可加工网格内的曲面片连接,从而获得荒加工区域.本算法剔除一般粗加工中无用的走刀路径,大大提高了复杂曲面类毛坯数控加工的效率.此算法避免了根据测量的离散数据点进行自由曲面造型,并通过曲面求交来获得荒加工区域.该算法已经应用于某汽轮机叶片的荒加工仿真,结果表明,该算法不仅效率高,而且结果非常理想.     

官地电站水轮机导叶漏水量试验研究

鉴于导叶漏水量是评定中高水头大型水轮机制造、安装和检修质量的重要指标之一,结合官地电站实际情况,利用计算机数据采集系统,分别采用斜井法和通气孔法对官地电站#2水轮机机组导叶漏水量进行测试。两种方法测试结果均表明,官地电站#2水轮机机组导叶漏水量满足国家标准要求。     

Effect of Bowed/Leaned Vane on the Unsteady Aerodynamic Excitation in Transonic Turbine

To investigate the effect of bowed/leaned vane configurations on the aerodynamic performance and aerodynamic excitation in transonic high-pressure turbine, the full three-dimensional viscous unsteady numerical simulation was performed by solving N-S equations based on SAS SST method.The influence of bowed/leaned vanes on turbine efficiency and efficiency fluctuation was investigated. The action of vane modelling to the overall aerodynamic fluctuation level and the amplitude of each vane passing frequency were analyzed. By comparing instantaneous pressure fluctuation contours in the blade passage with space-time maps, the link of the pressure fluctuation on blade surface with flow distortions was achieved, which can reveal the mechanism of the impact of the vane modelling. As the results suggest, the turbine efficiency is promoted with positively leaned and bowed vane modelling, and the fluctuation of stage turbine efficiency is repressed, which contributes to the smooth running of the turbine stage. The blade aerodynamic excitation on the rotor blade is characterized by the motion of vane trailing edge shock system, and the vane configurations can reduce the fluctuation level on the rotor blade surface effectively. For the positively leaned vane configuration, the aerodynamic excitations at the root and tip region are affected by the impact of the amplitude of the first harmonic, whereas they are reduced with the decrease of the amplitude of the second and higher harmonics at midspan. For the positively bowed vane, aerodynamic excitation is repressed by reducing the amplitude of the third harmonic at the root region, and the first harmonic at the tip region, and the amplitude of each harmonic is reduced at the middle region.     

计及功率与导叶开度非线性特性的混流式水轮机改进模型

针对现有理想水轮机模型和解析非线性水轮机模型不能反映混流式水轮机组功率与导叶开度间的非线性特性问题,建立了计及功率与开度非线性特性的混流式水轮机改进模型。该模型基于水轮机解析非线性模型,加入了功率与开度非线性关系模块,分析比较了功率与开度的不同拟合方法,推荐采用三次多项式拟合方法更适用于功率与开度拟合,并通过机组频率扰动试验、功率升降试验、一次调频试验和电网故障扰动试验仿真及实测结果表明,与理想水轮机模型和解析非线性水轮机模型相比,计及功率与开度非线性特性的水轮机改进模型精度更高。     

叶片开度对贯流式水轮机飞逸过程的影响

为有效降低水轮机飞逸过程中机组的振动问题,通过水轮机试验模型改变导叶开度和桨叶开度对水轮机过渡过程进行研究,分析了多个监测点的压力、频率流量等工作参数的变化情况。结果表明,由于转速和流量的增加,水轮机在导叶开度60°和桨叶开度4°运行时振动最为强烈,水轮机在低频时振动剧烈。由于受到导叶和桨叶动静影响,转轮出口振动强烈。导叶和桨叶慢速关闭能够降低压力脉动、轴向力、尾水管的真空度,但慢速关闭会增加负水锤,促进水轮机的破坏。使用遗传算法,通过加入权因子和罚因子,能够将水轮机多目标约束研究问题转化为单目标无约束研究问题,优化的导叶关闭规律对飞逸过程中出现的转速上升和压力上升有缓解作用,能够有效降低各点的振动。     

Performance of a 3 kW wind turbine generator with variable pitch control system

A prototype 3 kW horizontal upwind type wind turbine generator of 4 m in diameter has been designed and examined under real wind conditions. The machine was designed based on the concept that even small wind turbines should have a variable pitch control system just as large wind turbines, especially in Japan where typhoons occur at least once a year. A characteristic of the machine is the use of a worm and gear system with a stepping motor installed in the center of the hub, and the rotational main shaft. The machine is constructed with no mechanical breaking system so as to avoid damage from strong winds. In a storm, the wind turbine is slowed down by adjusting the pitch angle and the maximum electrical load. Usually the machine is controlled at several stages depending on the rotational speed of the blades. Two control methods have been applied: the variable pitch angle, and regulation of the generator field current. The characteristics of the generator under each rotational speed and field current are first investigated in the laboratory. This paper describes the performances of the wind turbine in terms of the functions of wind turbine rotational speed, generated outputs, and its stability for wind speed changes. The expected performances of the machine have been confirmed under real wind conditions and compared with numerical simulation results. The wind turbine showed a power coefficient of 0.257 under the average wind speed of 7.3 m/s.     

Numerical simulation on effect of pressure distribution of wind turbine blade with a tip vane

It is important to study the pressure distribution on the blade and in the adjacent area while searching the power augmentation theory with adding a tip vane to the wind turbine. This paper shows the CFD simulation relationship of the pressure distribution on the rotor blade and in the adjacent area, after calculating the pressure of the different chordwise and spanwise point on the blade with the tip vane-V(8.8×8) and without the tip vane under tip speed ratio λ 4.5. Combining the isobaric section figure in certain location, it can be seen that the tip vane improve the pressure difference between pressure and suction surface. The most influenced zone is found and these can further display the power augmentation theory of the wind turbine using the tip vane. The simulation calculation was based on N-S equations. 3-D, steady, implicit solver was chosen. Turbulence model was k-ω SST. Discretization scheme is SECOND ORDER UPWIND. Pressure-velocity coupling was a typical SIMPLE scheme. In the whole grid system, two-divided grid formation was adopted, that is, inner region and outer region. Inner region including rectangular solid blade and neighboring, outer region is semi-cylinder. There were together 720,000 nodes with tetra-prism unstructured mesh.     

双级贯流式超低比转速水轮机数值模拟优化

通过数值模拟等手段开发了一种双级贯流式超低比转速水轮机,利用循环冷却水出口的富余能量推动水轮机转动带动风扇旋转制冷,以达到节能目的。以富余流量0.823 m3/s的水轮机为例,以Fluent软件为平台进行计算分析,对双级贯流式超低比转速水轮机的叶片、导叶形式及其安放位置进行了优化,并采用Navier-Stokes方程、SIMPLEC算法对水轮机进行全三维湍流数值模拟,获得了水轮机内部流动细节,预估了水轮机的性能。计算结果表明,优化后的叶片及导叶表现出较高的效率。     

超低水头轴流式水轮机CFD优化及流动特性研究

结合某水电站改造要求,研发了一种设计水头为2.75 m的超低水头轴流式水轮机并对其性能进行优化,以达到有效利用低水头水力资源的目的。基于不可压缩连续方程及雷诺时均Navier-Stokes方程,采用Spalart-Allmaras湍流模型和SIMPLEC算法对轴流式水轮机进行三维全流场数值模拟,分别分析了轴流式转轮叶片翼型、轮毂比、导叶开度及安放角对水轮机性能的影响,并对最优模型进行实测验证。结果表明,在满足设计水头为2.75 m的情况下,选用配置叶片B、轮毂比为0.30、叶片相对安放角为-2°的水轮机,当导叶相对开度为0°时,装置水力损失最小,最高效率达83.7%,且数值模拟计算所得出力与实测结果误差小于099%,表明基于CFD的数值模拟对超低水头轴流式水轮机的性能预测精度较高。