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。     

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.     

Failure assessment of the first stage high‐pressure turbine blades in an aero‐engine turbine

In this paper, microscopic analysis and fatigue experiment were conducted to detect the damage degree of turbine blades after a 600 h service and determine the reliable service time. First, several service blades were cut into slices on different cross sections and microscopically examined. It is found that the γ′ phase particles are slightly coarsened and the γ′ phase parameters change with temperature and stress distribution. Then, fatigue test was conducted on service blades simulating the real working condition. The test result shows that the blades after a 600 h service would serve for 3596 h more until failure during actual flight. The ultimate fracture is mainly caused by the interaction of fatigue, creep and oxidation. Besides, the γ′ phase parameters change obviously compared with service blade without fatigue test. It indicates that the γ′ phase parameters could be used to evaluate the microdamage of service blades, which has great significance for service reliability of the turbine machinery.     

Failure of a low pressure turbine rotor blade of an aeroengine

During a test run of an aeroengine, a low-pressure turbine rotor blade had failed. The turbine blades were made of Ni-base superalloy of CM 247 LC grade and fabricated by DS investment casting. The blades were coated with platinum aluminide. Investigation revealed that the blade had failed by fatigue. It was concluded that the coating on the blade had developed cracks due to excessive bending/vibration, which in turn propagated by fatigue leading to the failure.     

Design of a fibrous composite preform for wind turbine rotor blades

The present work addresses the different factors and challenges one must cope with in the design process of a composite preform used for the load-carrying main laminate of a wind turbine rotor blade. The design process is split up into different key elements, each of which are presented and discussed separately. The key elements are all interconnected, which complicate the design process and involves an iterative procedure. The aim is to provide an overview of the process that governs the design of composite preforms for wind turbine blades. The survey can be used as an information source on composite preform manufacturing. Basic knowledge on wind turbine blade technology and composites is assumed.     

Acoustic emission detection of fatigue cracks in wind turbine blades based on blind deconvolution separation

The occurrence and expansion of fatigue cracks in large wind turbine blades may lead to catastrophic blade failure. Each fatigue phase of a material has been associated with a typical set of acoustic emission (AE) signal frequency components, providing a logical base for establishing a clear connection between AE signals and the fatigue condition of a material. The relevance of efforts to relate recorded AE signals to a material's mechanical behaviour relies heavily on accurate AE signal processing. The main objective of the present study is to establish a direct correlation between the fatigue condition of a material and recorded AE signals. We introduce the blind deconvolution separation (BDS) approach because the result of AE monitoring is usually a convoluted mixture of signals from multiple sources. The method is implemented on data acquired from a fatigue test rig employing a wind turbine blade with an artificial transverse crack seeded in the surface at the base of the blade. Two different sets of fatigue loading were conducted. The convoluted signals are collected from the AE acquisition system, and the weak crack feature is extracted and analysed based on the BDS algorithm. The study reveals that the application of BDS‐based AE signal analysis is an appropriate approach for distinguishing and interpreting the different fatigue damage states of a wind turbine blade. The novel methodology proposed for fatigue crack identification will allow for improved predictive maintenance strategies for the glass‐epoxy blades of wind turbines. The experimental results clearly demonstrate that the AE signals generated by a fatigue crack on a wind turbine blade can be synchronously separated and identified. Characterizing and assessing fatigue conditions by AE monitoring based on BDS can prevent catastrophic failure and the development of secondary defects, as well as reduce unscheduled downtime and costs. The possibility of using AE monitoring to assess the fatigue condition of fibre composite blades is also considered.     

燃气轮机转子系统典型振动特性试验研究

搭建气体轴承支撑的微型燃气轮机发电机试验装置,试验呈现微型燃气轮机发电机气体轴承-转子系统升速过程典型区域振动特征,并基于试验数据关联分析振动参数与燃气轮机运行参数、气体轴承的关键参数之间的耦合关系,结果表明:压气机出口压力波动对转子轴向振动影响较大;微型燃气轮机转子径向振动受点火压力波动、主燃料燃烧压力波动以及压气机...     

Investigation of the failure of the L-0 blades

A last stage (L-0) turbine blades failure was experienced at the 110 MW geothermal unit after 1 year of operation period. This unit has two tandem-compound intermediate/low-pressure turbines (turbine A and turbine B) with 23 in./3600 rpm last-stage blades. There were flexible blades continuously coupled 360 degrees around the row by loose cover segment at the tip and loose sleeve and lug at the mid-span (pre-twist design). The failed blades were in the L-0 row of the LP turbine B connected to the generator. The visual examination indicated that the group of 12 L-0 blades of rotor B on the generator side was bent and another group of 5 blades at 140 degrees from the first damaged group was also bent. The cover segments were spread out from the damaged blades and had cracks. Laboratory evaluation of the cracking in the cover segments indicates the failure mechanism to be high cycle fatigue (HCF), initiating at the cover segment holes outer fillet radius. The L-0 blades failure investigation was carried out. The investigation included a metallographic analysis of the cracked cover segments and bent blades, Finite Element Method (FEM) stress and natural frequency analysis (of blades/cover segments), fracture mechanics and crack propagation analysis. This paper provides an overview of the L-0 blades failure investigation, which led to the identification of the blades vibrations within the range 250–588 Hz induced due to unstable flow excitation (stall flutter) as the primary contribution to the observed failure.     

Developments of cast superalloys and technology for gas turbine blades in BIAM

Since 1960's many important subjects relating to cast turbine blades including alloy developments, directional solidification (DS) and single crystal (SC) technique and casting technology for blades have been performed with great successes in Beijing Institute of Aeronautical Materials (BIAM) in order to meet the requirements for developing new aero-engines in China.Abbreviations CC conventional cast - DS directional solidification - FC fine grain cast - SC single crystal     

汽轮机自带冠叶片碰撞减振的研究现状与发展

自带冠叶片冠间接触碰撞减振结构具有减振、方便安装与检修、制造精度要求低等优点,已广泛用于汽轮机设计制造并在多台汽轮机上安全运行多年,但目前对这种结构的减振机理和减振效果的研究却很不全面。结合国内外碰撞振动理论的研究成果,从自带冠叶片的碰撞振动特性、动力学模型、数值方法和实验研究等方面来介绍该领域的研究现状,着重阐述对该领域相关发展方向的一些看法,最后展望该领域以后需深入研究的几个关键问题。     

Cyclic strength of turbine blades made of cast nickel-based alloys

We study the cyclic strength and durability of service-exposed turbine blades made of IN-738, ZMI-3U, and éP539LM nickel alloys, some of them with a protective coating, upon a long operating time in gas turbine compressor sets. The blades of IN-738 alloy are found to have the highest cyclic strength. The cyclic strength of uncoated IN-738 blades is about 10% higher than that of coated blades. __________ Translated from Problemy Prochnosti, No. 2, pp. 5–14, March–April, 2007.     

空心涡轮叶片凝胶注模陶瓷浆料的设计与制备

为获得较低的黏度、较好流动性以及高固相含量的陶瓷浆料,采用同轴圆筒旋转黏度计,测试了不同配方双峰级配电熔刚玉粉体浆料的表观黏度,研究了粉体粒径、颗粒形貌以及级配比例对浆料流动性和固相含量的影响规律.研究表明:粗细颗粒的大粒径比、规则球形、宽粒度分布有利于制备低黏度高固相含量的陶瓷浆料.成功制备了表观黏度仅为0.411 Pa·s、固相含量为63%的陶瓷浆料,制备的陶瓷铸型在1 300℃下的强度大于18 MPa,烧成收缩率小于1%.     

Failure of a premix feeder line on a land-based gas turbine

A premix feeder line on a land-based gas turbine was found to be leaking, and the source of the leakage was traced back to a crack in a pipe-to-fitting weld. The weld joined a coupling made from the X6CrNiMoTi17-12-2 austenitic stainless steel to a type 316L austenitic stainless steel reducer. A root-cause assessment was conducted to determine the cause of the crack. Evidence of fatigue and corrosive attack was found. Various factors that influence the susceptibility to corrosion and cracking, such as heat tints, geometry of the weld, and surface finish of the component, are discussed. Recommendations are made for corrective actions and failure prevention.     

Failure analysis of a second stage blade in a gas turbine engine

The failure of a second stage blade in a gas turbine was investigated by metallurgical and mechanical examinations of the failed blade. The blade was made of a nickel-base alloy Inconel 738LC. The turbine engine has been in service for about 73,500 h before the blade failure at 5:50 PM on 14 August 2004. Due to the blade failure, the turbine engine was damaged severely. The investigation was started with a thorough visual inspection of the turbine and the blades surfaces, followed by the fractography of the fracture surfaces, microstructural investigations, chemical analysis and hardness measurement.

The observation showed that a serious pitting was occurred on the blade surfaces and there were evidences of fatigue marks in the fracture surface. The microstructural changes were not critical. It was found that the crack initiated by the hot corrosion from the leading edge and propagated by fatigue and finally, as a result of the reduction in cross-section area, fracture was completed.

An analytical calculation parallel to the finite element method was utilized to determine the static stresses due to huge centrifugal force. The dynamic characteristics of the turbine blade were evaluated by the finite element modal and harmonic analyses. Finally according to the log sheet records and by using a Campbell diagram there was a good agreement between the failure signs and FEM results which showed the broken blade has been resonated by the third vibrational mode occasionally before the failure occurred.     

The effect of crystallographic orientation on the natural vibration spectrum and fatigue limit of turbine rotor blades made of monocrystalline materials

Based on 3D models of rotor blades made of monocrystalline materils, the influence of crystallographic orientation of material axes on the formation of natural frequency spectrum and mode shapes of the blades has been clarified. A computational-experimental method is proposed for the evaluation of fatigue limit of monocrystalline blades, which significantly reduces the test scope while improving the reliability of test results. __________ Translated from Problemy Prochnosti, No. 5, pp. 15–27, September–October, 2008.     

Life assessment for a gas turbine blade under creep conditions based on continuum fracture mechanics

Based on the semi-analytic finite element method and relationships of the continuum fracture mechanics, a numerical investigation on the creep and extension of the continuum fracture zone in a gas turbine blade is performed. The value of life prior to the formation of a crack-like defect and applicability limits of the relationships of continuum fracture mechanics are determined. __________ Translated from Problemy Prochnosti, No. 4, pp. 87–93, July–August, 2006.     

舰用中冷回热燃气轮机装置动态性能分析

中冷回热循环（ICR）燃气轮机因其优越的全工况性能正日益受到船舶和工业领域的关注。通过分析ICR燃气轮机的变工况特性，采用模块化建模法仿真，对ICR燃气轮机进行动态性能分析，并与简单循环燃气轮机仿真结果进行比较。结果表明，换热器的热惯性对机组的动态性能影响较大，时间常数愈大，达到新平衡所需时问愈长；ICR燃气轮机不仅在设计工况点的效率和功率都有明显提高，而且在低工况下仍有良好的经济性，动力涡轮采用进口导叶面积可调可进一步改善ICR燃气轮机装置的部分工况性能。     

The effect of material behaviour on the analysis of single crystal turbine blades: Part II – Component analysis

This paper describes the analysis of a turbine blade component using a slip system model developed for modern single‐crystal superalloys. Structural elasto‐viscoplastic calculations are carried out for the component. The emphasis throughout is on the effect of micromechanisms of deformation, accounted for in the material model, on the predicted overall behaviour of the component. With the recent proliferation in detailed material models that are available, it is prudent to take a step back and investigate the implications of such models for component analysis and design. This effect is manifested through the determination of a stabilised and redistributed stress state throughout the component. While some components are creep‐limited in design, many are fatigue‐limited and it is stabilised stresses which control the cyclic life of these components. The accuracy of the material model, incorporating various micromechanisms as a function of stress and temperature, can significantly effect these stabilised stresses. The effect of the crystallographic orientation on blade behaviour is illustrated and the implications of shakedown simulations for fatigue lifing of turbine blades are discussed.     

Structural reliability analysis and uncertainties‐based collaborative design and optimization of turbine blades using surrogate model

In power and energy systems, both the aerodynamic performance and the structure reliability of turbine equipment are affected by utilized blades. In general, the design process of blade is high dimensional and nonlinear. Different coupled disciplines are also involved during this process. Moreover, unavoidable uncertainties are transported and accumulated between these coupled disciplines, which may cause turbine equipment to be unsafe. In this study, a saddlepoint approximation reliability analysis method is introduced and combined with collaborative optimization method to address the above challenge. During the above reliability analysis and design optimization process, surrogate models are utilized to alleviate the computational burden for uncertainties‐based multidisciplinary design and optimization problems. Smooth response surfaces of the performance of turbine blades are constructed instead of expensively time‐consuming simulations. A turbine blade design problem is solved here to validate the effectiveness and show the utilization of the given approach.