车用空调薄形冷凝器风扇的开发

通用采用宽幅前向叶片和将叶片弯曲率增大４０％，以及对叶片后缘进行锯齿形处理，不仅使风扇厚度减少了２０％，而且使风扇噪音比原来的风扇总计降低了７％。     

风力机叶片三维模型颤振问题

颤振对风力机叶片有巨大破坏力,作为一种典型的气动弹性稳定性问题,在现代风力机的叶片设计中越来越受到重视。建立叶片三维叶型模型和整机振动结构模型,利用振型叠加法计算不同振动模态下的特征频率、阻尼比和振型,得出不同叶片结构参数与颤振的关系。结果表明,叶片型面质心和扭转中心的距离、拍打方向弯曲刚度和挥舞方向弯曲刚度对颤振发生有较大影响。     

基于模态测试及有限元法的叶片失谐参数识别

针对现有叶片失谐参数选择及识别方法存在的不足,提出一种基于模态测试与有限元法相结合的叶片失谐参数识别方法。以某压气机一级叶片为研究对象,通过模态测试获得叶片一阶弯曲固有频率。对叶片弹性模量引入扰动参数,采用弹性模量改变模拟叶片失谐。基于有限元法识别出与叶片模态测试一阶弯曲固有频率对应的失谐扰动参数与失谐弹性模量,采用拟合计算获得各叶片失谐参数。结果表明:叶片失谐弹性模量与一阶弯曲无量纲固有频率测试值之间为近似线性关系;该方法识别速度较快且准确度高,可广泛应用于航空发动机、燃气轮机、汽轮机叶片的失谐参数识别。     

两自由度弯扭耦合涡轮机械叶片动力学分析

针对涡轮旋转机械的叶片所处的高温、高压及复杂多场环境,建立其弯曲和扭转两自由度耦合的截面模型,研究了来流速度对振幅的影响。利用平均法和能量法原理,得到了系统在发生临界颤振时的幅频关系以及在能量输入输出情况下系统的稳定性关系,避免了颤振发生引起的气动弹性设计失效问题,从而对叶片的优化设计提供理论依据。     

磁悬浮分子泵的振动抑制

2000L磁悬浮分子泵研制中,遇到复杂振动问题:转子弯曲模态共振;陀螺效应造成动力学失稳;叶轮叶片导致转子颤振;成因复杂的机电耦合模态振动.它们同时出现,严重影响转子稳定性,给振动抑制带来困难,需进行精细的控制器设计.控制器中,对不同振动采用不同方法抑制:陀螺效应依靠交叉反馈控制;弯曲共振、分子泵叶轮叶片颤振及机电耦合模态振动,依靠各种不同的控制器传递函数相位整形方法.试验验证了方法的有效性,分子泵平稳升速到24000 r/min,样机达到了设计真空性能指标.     

小流量下周向弯曲叶片间隙噪声实验研究

对带有周向前弯8.3°和周向后弯8.3°叶片的低压轴流风机,采用近远场动态压力测量技术,实验研究了小流量工况下叶顶泄漏流诱发的间隙噪声近远场声学特性,及周向弯曲叶片对间隙噪声的影响。结果表明:随流量的降低,周向弯曲叶片改变了泄漏流的强弱和迁移速度;在近远场功率谱的整个频域内,存在着由泄漏流诱发的间隙噪声,其具有宽频频率特性,这种低频特性随流量降低幅值逐渐增强,并向更低频段转移,周向前弯叶片向低频段迁移速度最慢;周向弯曲叶片对声学指向性的影响不同,周向前弯叶轮的声压级各个方向变化差异较大,而周向后弯叶轮变化较均匀。     

浅谈轴向双定位叶片综合测具的应用

文章介绍了根据定位、测量原理、公差分配原理,研究和设计的一种新型式的双向定位检测无余量叶片的测具结构。该测具采用了双向两点的轴向定位形式,体现了双向轴向点分担定位公差的理念,采用了空间连接的形式,满足了对叶片的5个叶身截面的型面测量(包括叶身扭转的状态)以及叶片上、下缘板的12个通道点测量功能。同时还要保证所有的定位机构、压紧机构满足叶片的扭转功能。这种情况的测具定位机构要注意它的稳定性及布局合理性;压紧机构要考虑操作方便、叶片与定位面贴合度要好。这样叶片在测量中能得到稳定数据,满足工艺对叶片测量的需求。     

振荡压气机叶栅叶片表面非定常响应以及气弹稳定性分析

发展并验证了一种适用于叶轮机内部非定常跨音流动诱导的叶片气弹问题的高效、准确的数值模拟方法。采用有限体积的多块结构化网格形式,多重网格方法加速收敛,隐式的双时间步时间推进,Spalart-Allmaras（S-A）湍流模型求解非定常雷诺平均Navier-Stokes方程。通过气动弹性标准算例10,叶片在高亚音和跨音流动下做弯曲振动,分析了流动状态、折合频率以及叶片间相位角对叶片表面非定常气动力响应以及叶栅气弹稳定性的影响。分析结果表明激波在此跨音振荡压气机叶栅中起失稳作用,叶片间相位角对气弹稳定性的影响在高折合频率下被加强。     

复合材料在大型风电叶片上的应用与发展

“30.60”双碳目标的提出,风电行业迎来新的发展机遇。随着中国风电进入平价时代,风电机组通过不断增加单机容量来降低度电成本,由此也对风电叶片长度提出了不断增加的要求。风电叶片面临着“大型化、轻量化与低成本”的矛盾,新材料和新工艺是推动叶片走向风电平价时代的重要手段。本文评述了风电叶片行业的发展与趋势,指出影响叶片性能和成本的关键原材料,系统性地分析了增强纤维、夹芯材料、基体树脂和结构胶4种材料在叶片上的应用现状和发展趋势;探讨了高质量和绿色环保条件下叶片大型化对工艺发展的新要求,新工艺中的预浸料和拉挤技术是未来大叶片应用发展的主要趋势。最后,文章对新材料和新工艺在叶片上的创新应用提出了一些思考与建议,为平价时代风电叶片的大型化发展提供了重要参考。     

某型发动机风扇叶片的损伤预测与振动分析

为了延长某型发动机风扇叶片的使用寿命,其关键在于如何准确地预测产生疲劳损伤的位置以及发动机工作时可能存在的共振状态,并针对性地采取相应措施。针对这一难点,应用Ansys软件建立叶片模型,并由模态分析测试验证其合理性,在此基础上建立叶片轮盘系统模型,对系统进行静力分析和有预应力的模态分析,成功地预测了叶片产生疲劳损伤的具体位置及系统共振时的形式、临界转速及频率。结果表明:叶片轮盘系统在不同离心转速载荷下等效应力分布方式相近,无明显变化规律,且叶片产生疲劳损伤的位置均为与叶高方向垂直的耳环处,及耳环与橼板的转接处;叶片轮盘系统不可能出现高频激振力引起的共振,可能会发生低频激振力引起的共振情况,且其形式为1阶弯曲振动,转速为8 425.51 r/min,频率为567.29 Hz。     

工业燃气轮机涡轮叶片用铸造高温合金研究及应用进展

工业燃气轮机具有热效率高、污染低等突出优点,成为未来发电机组与大型水面舰船动力的首选设备。铸造高温合金是工业燃气轮机涡轮叶片等热端部件的关键材料,其性能和制备水平在一定程度上决定了先进燃气轮机的功率、效率、寿命等性能。本文重点综述了工业燃气轮机及其涡轮叶片用铸造高温合金材料的研究及应用现状,并对工业燃气轮机涡轮叶片用铸造高温合金及涡轮叶片制造技术的发展趋势进行了展望。未来,先进定向凝固,“材料基因工程”等技术将逐渐应用到工业燃气轮机涡轮叶片用铸造高温合金的研制中;此外,先进工业燃气轮机上定向/单晶高温合金的应用将越来越广泛。     

Static and dynamic analysis of wind turbine blades using the finite element method

Analysis of forces and stresses of horizontal axis propellers and turbines has been the subject of increased interest in recent years because of the need to develop adequate analytical tools for the design and evaluation of-wind turbine rotors. Most of the structural failures of wind turbines occur in the blade root section. Hence, a three-dimensional analytical model to compute the deflection, stresses and eigenvalues in the rotor blades is proposed using bending triangular plate finite elements. Both membrane and bending stiffness are considered in deriving the element stiffness matrix. The consistent mass matrix is used in generating the overall mass matrix. Lift and drag forces created in steady wind conditions are analysed as normal and tangential forces on the blade sections at certain angles of attack. These forces are applied as boundary loads to the computer program to analyse statically and dynamically rotor blades of symmetrical aerofoil NACA 0015 series. Constant chord, tapered and twisted blades were analysed at rated and survival wind speeds. The validity of the computer program used was verified by applying it to a standard cantilever box beam using the beam theory. The results showed that maximum stresses occurred at the root of the blades for all configurations in the spanwise direction and that a tapered blade, in addition to saving material weight, diminished the stresses obtained. The twisting of the blade leads to an increase in stiffness and a decrease in the stresses.     

激光增材制造单晶高温合金研究进展

镍基单晶高温合金具有良好的高温强度、抗氧化和抗腐蚀性能、抗蠕变性能和组织稳定性,被广泛应用于制造航空发动机和燃气轮机叶片。由于其工作条件复杂恶劣,采用有效手段修复单晶叶片可以大大提高其使用寿命。综述了激光增材制造技术制备单晶高温合金的研究现状,介绍了激光增材制造技术制备单晶合金的理论基础,以及控制其单晶凝固组织的困难和不足,着重综述了激光增材制造技术控制单晶高温合金凝固制造的方法,主要包括通过激光参数调控温度梯度及凝固速率,以及通过基体晶体取向控制晶粒外延生长。最后,展望了该领域未来的主要研究方向和发展前景。     

Erosion failure mechanisms in turbine stage with twisted rotor blade

Blades of steam turbine are very important elements in power plant turbo aggregates. If blades of turbine fail, this will provoke further failures and high economical losses. Therefore, it is crucial to perform detailed research on reasons for failure of turbine blades to increase the reliability of turbine systems. The present paper deals with numerical simulation and research of erosion over blades in a low pressure stage of K-1000-6/1500 steam turbine working in a Nuclear Power Plant. Attention is paid to the effect of the amount of moisture in the stage; to the impact of droplets' diameter, their mass flow rate and forces acting on blade surfaces, to their aerodynamic behavior and influence on the energy conversion efficiency.Specific trajectories of water particles, reasons for the occurrence of erosion wear and erosion of certain parts of the streamlined surfaces are established and discussed. An approach to obtain incidence time to erosion effects appearance is formulated and implemented in the code. Research methodology and obtained results are applicable to determine specifics of erosion effects over streamed complex surfaces; replace expensive measurements campaigns; introduce approaches to decrease wetness in the last stages of condensation turbines and prolong the reliability of blades operated in wet steam conditions.     

The wear,deterioration and transformation phenomena of abradable coating BN–SiAl–bounding organic element,caused by the friction between the blades and the turbine casing

In modern design of gas turbines, the use of abradable materials for the coating seal of engines is widespread. Indeed, in order to increase efficiency of gas turbines, clearances between rotating blades and the casing should be as small as possible. Therefore, the blades scrape this BN–SiAl seal to form a minimum gap. The aim of this work is to investigate the behaviour of a particular abradable material, the BN–SiAl–bounding organic element, during interreaction with the blades under experimental conditions of operating the rotor blade. For this purpose, we use a Sulzer Metco abradability test. Tests are made with different incursion speeds of blade within the coating seal as well as linear blade velocities. The obtained results are shown in the form of graphs describing how the transfer of coating wear occurs and the different effects are observed on the coating surface.     

Mixed-flow vertical tubular hydraulic turbine: determination of proper design duty point

A new vertical single-regulated mixed-flow turbine with conical guide apparatus and without spiral casing is presented in this paper. Runner blades are fixed to the hub and runner band and resemble to the Francis type runner of extremely high specific speed. Due to lack of information and guidelines for the design of a new turbine, a theoretical model was developed in order to determinate the design duty point, i.e. to determine the optimum narrow operation range of the turbine. It is not necessary to know the kinematic conditions at the runner inlet, but only general information on the geometry of turbine flow-passage, meridional contour of the runner and blading, the number of blades and the turbine speed of rotation. The model is based on the integral tangential lift coefficient, which is the average value over the entire runner blading. The results are calculated for the lift coefficient 0.5 and 0.6, for the flow coefficient range from 0.2 to 0.36, for the number of the blades between 5 and 13, and are finally presented in the Cordier diagram (specific speed vs. specific diameter). Calculated results of the turbine optimum operation in Cordier diagram correspond very well to the adequate area of Kaplan turbines with medium and low specific speed and extends into the area of Francis turbines with high specific speed. Presented model clearly highlights the parameters that affect specific load of the runner blade row and therefore the optimum turbine operation (discharge—turbine head). The presented method is not limited to a specific reaction type of the hydraulic turbine. The method can therefore be applied to a wide range from mixed-flow (radial-axial) turbines to the axial turbines. Applicability of the method may be considered as a tool in the first stage of the turbine design i.e. when designing the meridional geometry and selecting the number of blades according to calculated operating point. Geometric and energy parameters are generally defined to an extent that these parameters are considered in detailed design using turbulent viscous flow CFD solver.     

Failure of last-stage turbine blades in a geothermal power plant

This paper presents an investigation into causes of failure of geothermal steam turbine blades. Several L-0 blades of geothermal steam turbines of 110 MW capacity suffered failures, causing forced outages of the turbines. To assess the causes of failure, the natural frequencies of the blades installed on the rotor were measured in the laboratory. The measured frequencies were compared with the natural frequencies calculated through a finite-element analysis (FEA) of the blade. The FEA was also used to calculate the vibratory stresses on the blade numerically. Also, the investigation analyzed the operational data and the history of the blade failures on several rotors of different units from the same system. The results of previous repairs were reviewed, and metallurgical investigations were conducted to identify the mechanical and metallurgical modes of failure. The results of the investigation showed that the fracture of two blades was attributed to installation and manufacturing errors and aggravated by general deterioration of the blades. The deterioration was caused by the erosion and corrosion process that resulted from moisture condensation in the steam.     

Welding repair by linear friction in titanium alloys

Abstract

Gas turbines for aeroengines are generally manufactured by attaching individual blades into slots in the disk. However, an alternative design consists in producing bladed disks, where disk and blades are a single piece. Previous studies have shown that linear friction welding is a technology which fits well for this application. On the other hand, bladed disks can experience in service damages and therefore affordable repair technology must be available. The present paper presents the microstructural and mechanical evaluation of double and triple welds produced to simulate replacements of damaged blades. The results show that, even though the successive welds induce a small strength decrease, both tensile and fatigue failures always initiated far away of the weld zone.     

Composite materials for wind energy applications: micromechanical modeling and future directions

The strength and reliability of wind turbine blades depend on the properties, mechanical behavior and strengths of the material components (glass or carbon fibers and polymer matrix), and the interaction between them under loading. In this paper, ideas, methods and concepts of micromechanical modelling of materials for wind turbine blades are briefly reviewed. Using the variety of the modeling methods reviewed here, one can predict the strength, stiffness and lifetime of the materials, optimize their microstructures with view on the better usability for wind turbines, or compare the applicability of different groups of the materials to the application in wind turbine blades. Some examples of the analysis of the microstructural effects on the strength and fatigue life of composites are shown.     

Abrasion predictions for Francis turbines based on liquid–solid two-phase fluid simulations

The runner blades and guide vanes of Francis turbines are worn by sediment in the flow. However, there are few studies about abrasion of the runner blade and guide vane for normal turbine operating conditions. This study investigated the relation between the wear rates on the surfaces of the runner blade and guide vane and the sediment concentration, and analyzed the distribution of the wear rates for normal turbine operating condition. An Eulerian–Lagrangian Computational Fluid Dynamics (CFD) procedure was used to simulate steady liquid–solid two-phase flow for various operating conditions. The Finnie model was then used to predict the abrasion. The conditions leading to abrasion in the inner flow passage components of a Francis turbine are clarified through analysis of the abrasion conditions for the runner blades and guide vanes. Field tests and simulations show that the relative wear rate on the runner blades and guide vanes increases with increasing sediment concentration, and the maximum wear on the runner blades occurs in a small opening region with the maximum increasing as the head increases. The maximum wear on the guide vanes occurs at the maximum output and the relative wear rate on the runner blades is much greater than that on the guide vanes. There is no good data, so the relative wear rates on the runner blades and the guide vanes can only be obtained numerically. Thus actual wear rates cannot be given and are beyond the scope of this paper. This paper shows the abrasion characteristics on the runner blades and guide vanes with sediment flow and provides reference data for predicting the abrasion conditions in the flow passage components of a Francis turbine.