Finite Element Approach for Failure Analysis of a Gas Turbine Blade

Journal of Failure Analysis and Prevention - In the present work, a case study on the gas turbine blade is undertaken for failure analysis through finite element approach. The analysis is carried...     

燃料气换热器管束鼓包开裂分析

某燃料气换热器在运行过程中发现其换热管束出现多处鼓包开裂现象,为查明鼓包开裂原因,对换热管束进行了宏观和微观检验、化学成分分析、金相检验和扫描电镜分析。结果表明:换热管内存在压力波动、换热管壁厚不均匀、壳程介质H2S含量较高以及换热管材料中存在,夹杂物都是导致其鼓包开裂的原因;换热管壁厚较薄处容易形成应力集中,使该处硫化氢腐蚀严重,壁厚进一步减薄,当壁厚减薄达到一定值时,在管内压力波动作用下形成鼓包,随着腐蚀的加剧和压力波动的继续作用,最终导致换热管于鼓包处产生裂纹,进而发生泄漏。     

Failure Investigation of a Gas Turbine Inlet Weatherhood

Analytical and experimental methods have been used to investigate fatigue failures in the weatherhood protecting the air inlet to an offshore gas turbine power generation unit. A simple method for modelling transverse vibration of the leading edge is described, and the results are compared with experimental measurements made on a prototype installation. Calculation of the stresses induced at the critical locations, where cracking has been observed, suggests the failure should be attributed to aerodynamic excitation of the leading edge.     

某酸性气田集输管线三通管件裂纹失效分析

某酸性气田集输管线16Mn钢三通管件服役1a(年)后出现裂纹,通过宏观分析、化学成分分析,硬度测试、金相检验、腐蚀产物分析以及扫描电镜断口分析等方法,对三通管件的开裂原因进行了分析。结果表明:三通管件开裂为硫化物应力腐蚀开裂,材料硬度偏高和存在上贝氏体组织是造成管件发生硫化物应力腐蚀开裂的主要原因。建议严格控制三通管件原材料复验以及产品质量检验,同时定期对气田在役三通管件等关键部位进行无损检测,包括探伤、硬度检测等,预防类似事件的再次发生。     

Failure Analysis of Nozzle Guide Vane of a Low Pressure Turbine in an Aero Gas Turbine Engine

Failure of low pressure turbine nozzle guide vane (NGV) in an aero gas turbine engine is analyzed to determine its root cause. Forensic and metallurgical investigations are carried out on the NGV failed as well as the failed components of the downstream modules. Failure in the cooling system in the NGV due to crack in the sealing plate was found to be the cause of NGV getting burnt. This failure has caused extensive damages in low pressure turbine modules. Remedial measures are also suggested to prevent such failures.     

Multidisciplinary Design Optimization Procedure for Improved Design of a Cooled Gas Turbine Blade

A multidisciplinary optimization procedure for gas turbine blade design has been developed and demonstrated on a generic 3-D blade. The blade is cooled both internally and externally (film cooling). Aerodynamic and heat transfer design criteria are integrated along with various constraints on the blade geometry. The blade is divided into numerous spanwise sections and each section is represented by a Bezier-Bernstein polynomial. A comprehensive solver for 3-D Navier-Stokes equations is used for the viscous flow calculations. The finite element method is used to obtain the blade interior temperatures. The average blade temperature and maximum blade temperature at each spanwise section are minimized, with aerodynamic and geometric constraints on the blade geometry. The constrained multiobjective optimization problem is solved using the Kreisselmeier-Steinhauser function approach. The results for a generic turbine blade design problem show significant improvements after optimization.     

Failure Analysis of High-Pressure Compressor Blade in an Aero Gas Turbine Engine

Failure of high-pressure compressor rotor blade in an aero gas turbine engine is analyzed to determine its root cause. Forensic and metallurgical investigations are carried out on the blade and failed parts. The failure of the platform ladder is found to the first in the chain of events that led to the compressor blade failure. The mode of failure in the blade is found to be fatigue and has originated from the damaged region on the leading edge caused by dislodgement of platform ladder. The failure has caused extensive damages in high-pressure compressor module and also in downstream turbine blades as a secondary effect.     

齿轮开裂失效分析

采用断口分析、化学成分分析、低倍检验、金相检验和硬度测试等方法对某批经渗碳、淬火热处理及磨齿加工后放置一段时间发生开裂的齿轮的失效原因进行分析。结果表明：齿轮渗碳层碳化物级别过高,加上淬火后齿轮齿部应力集中,磨齿时又产生磨削裂纹,齿轮在放置期间由于应力导致裂纹扩展而开裂。     

二极管裂纹失效分析

大功率和短波激光二极管在810nm波长时,其最大输出功率为100mW.它要求在实际工作条件下达到高可靠指标(MTTF应超过5000h).为了保证高可靠性,该二极管内采用了长空腔和金刚石子支架.但是,在试生产期间,经过温度循环之后,一些样品发生了光电失效.失效样品的破坏性物理分析(DPA)显示,二极管芯片上的裂纹把芯片分成两部分.因此,空腔受到芯片裂纹的破坏而导致失效,为了查找二极管芯片产生裂纹的工序和原因,我们重复了激光二极管原来的组装工序,对每个工序中的样品做了检验,并观测到:     

燃汽轮机发电机铸造风扇开裂分析

某意大利进口的燃汽轮机发电机铸造风扇在国内安装使用2 a后发生早期开裂事故。从低倍组织、断口形貌、显微组织和力学性能等方面对风扇开裂原因进行了分析,并利用有限元软件对风扇的小环应力分布进行了计算。结果表明:该风扇开裂的性质为低应力累积损伤所致的疲劳开裂,开裂的主要原因是风扇裂纹源部位存在较多的裂纹、显微疏松孔洞等补焊缺陷以及在补焊后未能进行适当的热处理。     

Failure Analysis and Repair of a Catastrophically Damaged Gas Turbine Compressor Disk Using SEM Technique and CFD Analysis

During a major overhaul of an 85?MW gas turbine unit in Iran-Rey power plant, 39 cracks were detected with different lengths and locations on the compressor disk of stage 11. All of the cracks initiated from the dovetail regions. Preliminary visual inspections and further micro-fractography using the scanning electron microscope demonstrated that the fretting fatigue phenomenon was the main cause of failure. Four repair methods were suggested to restart the unit. The first one was to remove all of the cracks from the disk by machining, or the so-called blending. The second, third, and fourth ways were to remove the entire rotor blades of stage 11, to remove the entire rotor and stator blades of the stage 11 simultaneously, and to remove those rotor blades of stage 11 corresponding to the damaged dovetails, respectively. Although the first way of solution was initially carried out on the damaged disk, the first author offered that restarting the unit with the blended disk is not reliable enough because of the presence of a large number of repair points on the disk. Using the numerical investigations based on the computational fluid dynamics, it was found that only the second suggestion (i.e., removing the entire rotor blades of the stage 11) might be applicable. Ultimately, the entire stage 11 rotor blades were removed from the blended disk, and the gas turbine unit was successfully restarted without encountering abnormal operation. Although the performed process resulted in approximately 20% output power loss compared with the unit's power before the blades' removal, the unit was quickly restored to be ready to restart, and the electric power could be generated during the period of peak consumption.     

钛合金螺母开裂原因分析

钛合金螺母在使用过程中发生了开裂,采用化学成分分析、金相分析、微观观察等方法对开裂螺母进行了分析。结果表明螺母的开裂是由于应力腐蚀造成的,并提出改进措施。     

Failure Analysis of Ethylene Cracking Tube

Radiant tubes of an ethane furnace at a petrochemical plant fabricated from an austenitic heat resistant steel casting (HP grade) failed along longitudinal direction after a fraction of anticipated service life. To study the cause of failure, microstructures of as-received and used tubes were investigated by optical and scanning electron microscopy and the microchemical composition of tubes and precipitated carbide were determined by energy dispersive X-ray (EDS). Also, the morphology of deposited coke particles was determined by SEM/EDS. Finally to measure the extent of carbon penetration, hardness testing was performed on the inner and outer surface of tube. The experimental results show that the improper coking and decoking cycles remove the protective oxide layer (Cr₂O₃) that forms on the exposed surfaces and that, with this layer removed, the coke could easily deposit on inner, non-protected surface. The carbon diffusion into the metal was accelerated with deposited coke and caused microstructural degradation and drastically reduced the ductility of material at high temperatures.     

Analysis of Low-Pressure Turbine Nozzle Guide Vane Failure in an Aero Gas Turbine Engine: A Computational Approach

Journal of Failure Analysis and Prevention - Failure of low-pressure turbine nozzle guide vane (NGV) in an aero gas turbine engine is analyzed using computational approach. Breakage in the cooling...     

某燃气轮机压气机叶尖间隙的分析

设计合理的燃气轮机的叶尖间隙,一直是业内人士非常关注的问题.针对中国某改进型燃气轮机的压气机,在综合考虑材料热膨胀的影响、离心载荷作用下的径向应变、叶片轮盘和机匣的材料代用、轴承的游隙、以及弹性支撑等影响因素共同作用的前提下,通过对机组稳态和过渡态运行工况的叶尖间隙计算,最后给出了改进型压气机动/静转子间的安装间隙.     

Failure Prevention of Gas Turbine Blades Through Pack Aluminization

Pack aluminization of low-pressure turbine blade of an aero gas turbine engine has been carried out following a well-defined systematic procedure. The process parameters are first optimized on dummy blades, and optimized process is followed for the actual blades for evaluation and testing. Visual and binocular examination followed by metallurgical evaluation has been carried out to validate the process and to establish the adequacy and correctness of the coating. The coated blades are then evaluated through component-level test and engine-level test followed by field evaluation trials for performance and durability. The results of engine-level tests and inspection post-accelerated mission test cycles ensure that the blades with aluminide coating can withstand severe engine operating cycles without any damage or failure which otherwise would have experienced. The failure-free operation for an equivalent TBO life and post-AMT condition of blades are an indication of enhanced life of aluminide blades and prevention of failure of the turbine blades through pack aluminization.     

弹壳开裂失效分析

对某型H68黄铜弹壳进行检查时发现大量弹壳存在裂纹。通过对弹壳进行宏观和微观观察、能谱分析、金相检验和残余应力测定等,分析了弹壳开裂的原因。结果表明:弹壳的开裂性质为应力腐蚀开裂,其原因是由于收口位置存在一定的残余拉应力,且该位置的晶粒尺寸较大,在外界介质的协同作用下产生了应力腐蚀裂纹。