GHH风机动叶片飞裂的原因和预防

GHH风机动叶片飞裂，造成很大的经济损失。调查中发现动叶片的材料作了改动和发现，一、二、三级动叶片出现冲蚀磨损。本题的成分、实物性能、组织、断口分析证明材料改动不是失效的主要原因。进一步的叶型测定和叶片强度校核结果证明，动叶片的冲蚀磨损是失效的主要原因。根据本风机的股役环境，提出可行的预防措施，受到使用部门的重视和赞许。     

转子突加不平衡响应试验及数值研究

叶片飞脱引起的转子不平衡瞬态响应是备受关注的重要问题之一。为研究某小型发动机叶片飞脱后的不平衡响应,在高速旋转试验台上进行叶片飞脱试验,测量转子的位移数据,并用高速相机记录叶片飞脱过程。运用传递矩阵法建立了单盘双支承转子系统的运动方程,用Newmark-β法积分求解,模拟了转子在双叶片顺序飞脱下的不平衡响应。试验和计算结果表明,叶片飞脱后的转子振动存在剧烈振荡、慢速涡动和平稳振动三个阶段。     

261P-7型增压器涡轮叶片裂纹及飞裂故障分析

我厂生产的261P增压器能较广泛与各型柴油机配套使用,多年来束发生过涡轮叶片断裂事故,叶片材料为GH130。78年在配试广州及宁波的6G300ZC柴油机(额定400转/分,加增压功率1200马力)过程中,分别发生了涡轮叶片飞裂及裂纹故障,故障机台数为广州厂2台,宁波厂1台,分别编号为1号、2号、3号,故障情况见图1。叶片开裂及飞裂的部位均是一致的,裂纹均是由排气边起始向内延伸,图2、3。a=17.5～20毫米,b=9～11毫米。     

基于流固耦合的混流式水轮机转轮应力分析

混流式水轮机转轮在正常运行时,会因为水利因素导致转轮叶片发生疲劳断裂或者出现裂纹,为了让机组在合适的工况和频域区间运行,避免因为应力或是振动等问题发生叶片失效。基于流固耦合理论,采用顺序耦合法,通过建立转轮模型、CFD分析、流固耦合应力分析以及振型仿真等操作,分析额定工况和飞逸工况下的运行规律。     

极限载荷作用下风力机叶片跨尺度分析

跨尺度分析是风力机叶片力学性能研究的重要方法,首先对风力机叶片在极限载荷作用下进行有限元分析;然后结合最大正应力准则及桥联模型将叶片的宏观响应传递到细观模型,对叶片进行细观失效分析;最后依据Tsai-Wu失效准则和层合板理论将细观材料强度转换为宏观层合板强度,对叶片进行宏观失效分析。仿真与理论的结果表明：根据该方法可以判断风力机叶片在不同尺度下是否出现失效以及出现的失效形式;同时可以完成跨尺度的材料强度预测,对风力机叶片的失效预测具有重要的工程价值。     

汽轮机叶片裂断原因与防范措施

汽轮机的动叶片是受蒸汽推动力和转子高速转动产生离心力的通流部件,其本身几何形状和安装方式存在着固有的振动频率,在设计、制造、运行中动应力、离心力超标或产生共振疲劳,将会导致叶片裂断。另外,进入汽轮机的蒸汽必须保持足够的过热度和参数的准确,若蒸汽带水或从抽汽口返水进入汽轮机,将使推力急剧增大,转子后移,造成推力瓦烧损及动静碰摩,叶片受伤而裂断。     

汽轮机低压扭叶片强度和振动的可靠性分析

针对汽轮机和整个电站的安全工作问题,对汽轮机动叶片进行了安全可靠性分析,以某汽轮机低压扭叶片为例,研究了其强度振动可靠性。首先确定了叶片材料、转速以及蒸汽流量等随机变量的分布类型,同时采用了确定性有限元分析法、二阶多项式响应面法和Monte-Carlo模拟法相结合的方法,确定了低压扭叶片静强度、动强度及振动的可靠度;同时,研究了随机变量对强度和振动的概率敏感性。研究结果表明:静强度、动强度及振动可靠度分别为R=1.0,R=0.98,R=1.0,当同时考虑强度和振动失效模式时,叶片强度振动设计的可靠度R=0.98,未能达到99.73%的要求(±3σ准则);材料密度分散性对强度和振动影响最为明显,须对材料密度分散性进行严格控制。     

汽轮机低压转子2Cr13不锈钢叶片断裂分析

通过断口宏观形态分析、扫描电镜(SEM)微观观察、能谱(EDS)分析和显微组织分析以及常规力学性能测试,对电站汽轮机低压转子2Cr13不锈钢叶片断裂失效模式和失效原因进行了全面的分析,并对开裂机制进行了深入探讨.结果表明:该汽轮机低压转子2Cr13不锈钢叶片的失效模式为腐蚀疲劳破坏,叶片材质较差的内部因素和腐蚀疲劳的工况条件共同作用造成了叶片的断裂失效.     

催化裂化轴流压缩机叶片疲劳断裂原因分析

介绍了某催化裂化轴流压缩机叶片断裂的情况,并通过对可能导致叶片疲劳失效的几个因素进行分析,得出叶片断裂失效的原因是叶片共振。     

汽轮机叶片可靠性的统计分析

介绍了汽轮机叶片可靠性的基本概念和评价指标,单个叶片、整级叶片的失效判据和失效模型,以及叶片寿命数据的统计分析方法.给出了汽轮机典型叶片可靠性分析和预测实例.     

Investigation of blade failure in a gas turbine

A gas turbine abruptly tripped to a stop during its daily morning start-up period. Out of a total of 81 blades in the first row only one blade was broken at its root. Prior to this accident, there were three blade failure accidents in the same plant during the last 10 years. First, the fracture surface of the troubled blade was investigated. Stress analysis of the blade showed that the maximum stress occurred due to the pressure profiles developed during operation. Modal analysis for one blade and the assembly of blades was performed and Campbell diagram and Interference diagram were drawn to check the dynamic characteristics of the blades. The vibration of the turbine was measured using accelerometers during the operation condition. The result shows that the fatigue fracture of the blade was originated during transient events internal to the combustion chamber which was close to the resonance condition of the assembled blades.     

Failure analysis of gas turbine generator cooling fan for 14° and 19° — blades angle of attack

In gas turbine power plants, a fan is used as a cooling system to dissipate generated heat in coils (copper conductors) and generator electric circuits at the end sides of its rotor. In some cases, fracture of blades causes short circuit between rotor and stator and consequently generator explosion and made lot of financial problems. The fracture of cooling fan blades has been occurred five times at the turbine side of the generator in our case of study, just 100 hr after resuming operation after overhaul. Using numerical analysis as well as laboratory investigation — includes visual inspections, metallography and SEM — can help better finding failure problems that cause blade failures. A series of numerical analysis was performed to diagnose the cause of failure possibility. CFD analysis is used to study the airflow distribution in order to observe probable separation phenomenon and pressure forces that they are imposed to fan blades due to operation. A finite element method was utilized to determine the stresses and dynamic characteristics of the fan blade (natural frequencies, stresses and vibrations).     

基于失效分析法与FTA法的叶片安全性研究

近年来我国沿海钻井平台使用的不同型号的燃气轮机曾发生叶片断裂事故,造成严重损失。为了更好解决燃气轮机叶片断裂的分析、预防与维护等问题,在应用裂纹分析技术及断口分析技术进行叶片失效分析的基础上,建立燃气轮机叶片故障树,运用故障树定性分析原理,对叶片进行故障根本原因推理,结合失效分析与故障原因分析所得的结论,提出了针对性的预防维护建议。将此方案成功应用于工程实践,对于燃气轮机叶片的安全可靠运行提供良好的保障。     

航空发动机叶片刚柔耦合动力学分析

航空发动机叶片是航空发动机重要零件之一,常常因共振而导致断裂失效。传统航空发动机叶片的振动特性分析普遍基于零次近似耦合动力学模型,该模型忽略了动力刚化项,得到的结果具有一定局限性。为了更加准确地分析高速转动的航空发动机叶片的振动特性,对叶片刚柔耦合动力学问题进行了研究。将叶片简化为柔性薄板,考虑面外变形和面内变形,并计入了面外变形引起的面内变形,即变形耦合项。采用假设模态法描述叶片的变形,运用拉格朗日动力学方程建立了做三维空间大位移运动的柔性叶片一次近似耦合动力学方程。同时采用多体系统动力学软件MSC.ADAMS对旋转叶片的动力学性态进行了研究,并将所得的叶片动力学理论模型结果和ADAMS的结果进行了比较。结果显示一次近似耦合模型理论结果与实际结果相符,而ADAMS和零次近似耦合模型在叶片高转速时仿真结果存在缺陷。基于所得的叶片一次近似耦合模型,对叶片振动频率、“频率转向”和“振型转换”问题进行了分析,验证了所提出的方法的可行性。     

叶片疲劳应力幅的断口特征形貌判断

归纳总结了叶片疲劳断口的特征形貌。宏观疲劳断口的特征形貌主要有宏观疲劳源或疲劳源区的疲劳沟线、疲劳扩展距离、疲劳断口的粗糙度,微观疲劳断口的待征形貌主要有微观疲劳条带间隔、二次疲劳裂纹和韧窝形貌等。然后讨论了通过疲劳断口特征形貌的定性分析或定量分析诊断疲劳应力幅大小的可能性和值得注意的问题。     

某离心压缩机首级叶轮叶片断裂事故分析与改进研究

本文研究了某离心压缩机首级叶轮叶片断裂事故。分析了该叶片发生断裂的原因,发现该事故主要是由于叶轮固有频率与进口导叶尾迹频率接近发生共振引起的。在此分析基础上,提出了以下改进措施：一方面通过增加叶片厚度来改变叶轮固有频率,以避开进口导叶尾迹频率;另一方面,同时通过叶片进口处沿轴向切除14.4mm,以减小进口导叶尾流激振力。到目前为止,改进后的叶轮现场运行情况良好。     

Modal characteristics according to the tip shape and assembly condition of the turbine blade

To determine the reliability of a 5 MW gas turbine engine blade in high cycle fatigue (HFC) fracture being developed by Doosan Heavy Industries & Construction Co., Ltd., resonance characteristics are verified based on the turbine blade tip shape and assembly condition. In this study, the modal characteristics of compressor and turbine blades are investigated, and a Campbell diagram is established. During the preliminary study, modal analysis and holographic modal test of the first-, fifth-, and tenth-stage compressor blades were performed. Based on the preliminary study result, the natural frequency and Campbell diagram analysis for the turbine blades were performed. This research compared and verified the modal characteristic and resonance stability according to the tip shape and assembly condition of the blade to prevent any HCF fracture. In conclusion, the resonance stability of the shrouded blade is far superior to that of the squealer blade. Suitable assembly conditions must be applied.     

Modal characteristics and fatigue strength of compressor blades

High-cycle fatigue (HCF) has been identified as one of the primary causes of gas turbine engine failure. The modal characteristics and endurance strength of a 5 MW gas turbine engine blade developed by Doosan Heavy Industries & Construction Co., Ltd. in HCF fracture were verified through analysis and tests to determine the reliability of the compressor blade. A compressor blade design procedure that considers HCF life was performed in the following order: airfoil and blade profile design, modal analysis, stress distribution test, stress endurance limit test, and fatigue life verification. This study analyzed the Campbell diagram and estimated resonance risk on the basis of the natural frequency analysis and modal test of the compressor blade to guarantee safe and operational reliability. In addition, the maximum stress point of the compressor blade was determined through stress distribution analysis and test. The bonding point of the strain gage was determined by using fatigue test. Stress endurance limit test was performed based on the results of these tests. This research compared and verified the modal characteristics and endurance strengths of the compressor blades to prevent HCF fracture, which is among the major causes of gas turbine engine damage. A fatigue life design procedure of compressor blades was established. The 5 MW class gas turbine compressor blade is well designed in terms of resonance stability and fatigue endurance limit.     

Wear of the blade diamond tools in truing vitreous bond grinding wheels: Part I. Wear measurement and results

The wear of stationary blade diamond tools used to generate a precise and intricate form on the vitreous bond grinding wheel is presented. Two types of blade tools made of rod and particle diamond were used. A method to measure the wear of the blade diamond tool in the μm-scale range using the size difference of two parts ground before and after truing was introduced. Two sets of experiments with four truing feeds and four tool traverse speeds across the grinding wheel were conducted on the rod and particle blade diamond tools, respectively. Experimental results showed the wear rate of blade diamond tools was improved at higher truing feeds and traverse speeds due to the brittle fracture of the abrasive and vitreous bond.     

定向凝固合金叶片的裂纹与再结晶研究

对定向凝固合金叶片的裂纹进行分析，在断口观察与金相组织分析的基础上，对叶片的失效模式与失效原因进行研究，并提出预防该类故障发生的措施。研究结果表明，定向凝固合金叶片的裂纹是由于叶片表面的再结晶而导致的。叶片表面的再结晶在叶片使用之前就已存在，是由于固溶热处理前叶片的表面存在塑性变形，在固溶热处理过程中形成的。