汽轮机低压叶片断裂原因分析

针对国产300MW汽轮机低压缸扭叶片发生断裂失效事故进行研究分析;通过对扭叶片有限元计算、叶片振型模态实测,分析该叶片各阶自振频率,其计算结果和模态实测值基本吻合,为事故分析提供理论依据;对叶片材质元素成分测试,并着重对叶片实际运行工况及承受的各种可能的激振力分析,探求导致该级扭叶片疲劳断裂的真实原因,为同类型机组的安全、可靠运行提供一种借鉴作用和分析方法.     

汽轮机通流部分优化设计

本文主要对高效新叶型的开发、子午通道优化技术、弯扭联合成型技术和新型汽封的应用等汽轮机通流部分性能的改进与优化措施方面进行了回顾与总结,并对汽轮机多目标优化现状进行分析,在汽轮机效率的提高方面进行了一定展望。     

循环对称算法及其在汽轮机叶盘系统振动分析中的应用

用三维实体单元来离散汽轮机整圈叶片和轮盘,并针对由此带来的庞大自由度的问题,根据结构的循环对称特性,引入循环对称算法,通过对一个扇形子结构进行计算,成功地完成了对整个结构的动力特性分析.在理论分析的基础上,本文用FORTRAN语言编制了适用于循环对称结构的振动特性分析有限元程序,以及相应的前后处理程序,并进行了算例验证,证明由循环对称算法得到的结果与整体算法得到的结果完好吻合,同时极大地减少了计算时间.作为所述方法的工程应用,分析了某汽轮机第6级整圈扭叶片-轮盘系统的振动特性.     

浅谈弯扭叶片的作用机理及实践应用

目前,弯扭叶片在工程实践中得到了广泛的应用,使透平机械的效率得到了大幅度的提高。文章对弯扭叶片的作用机理进行了阐述,并对其在工程实践中的应用进行了介绍。     

风力机复合材料柔性叶片的颤振分析

将风力机叶片简化为薄壁复合材料封闭截面弯扭耦合变形梁,基于Hamilton原理并结合变分渐进法（VAM）,建立风力机叶片的气动弹性力学模型。结构模型包括材料各向异性,截面翘曲,离心载荷,科里奥利加速度,以及预锥角和预扭转角的影响。气动载荷采用叶素动量理论和准定常气动力理论进行描述。将位移按广义坐标进行模态展开,采用Galerkin法导出系统的质量、刚度和阻尼矩阵,采用特征值技术进行叶片颤振性能的数值求解。针对周向反对称刚度配置（CAS）叶片进行数值近似计算,揭示了入流比、预扭转角和纤维铺层角等参数对风力机叶片颤振性能的影响。     

轧机主传动系统扭振盲测点测量模型的研究

为解决轧机主传动系统实际测试中不可测点处物理参数测取的难题，构造了一类连续轴段质量扭振分析模型，并推导出轴段上盲测点处的扭振参数计算公式。通过把实测点的测试数据代入盲测点计算公式，可计算盲测点的振动参数。轧机实际现场扭矩测试和数据分析处理结果验证了理论推导的正确性。这为轧机现场监测中一些不易布置传感器关键点处的物理量测取提供了理论依据和技术支持，通过编制程序可以实现轧机在线系统监测和故障分析，从而确保轧机正常平稳运行。     

简支超静定梯形斜梁桥变形的分析计算及其参数研究

本文用斜梁挠曲扭转微分方程，导出了简支超静定单梯形斜梁在常见荷载下的变形计算公式，并就其弯曲扭刚度比Ｋ，斜交角Φ，荷载型式及平面型式等参数对变形特性的影响进行了分析讨论，可供设计部门参考。     

磁粉探伤在汽轮机叶片质量检测中的应用

我们知道汽轮机动叶片形状复杂,动叶片在精加工后的表面如果存在表面裂纹、折叠、夹杂、缩孔等缺陷将对汽轮机运行带来严重的影响。所以需要对汽轮机叶片的工作状况进行剖析,给出了叶片质量的荧光磁粉探伤检验措施,并且对一些伪磁痕现象进行查找并且消除,为汽轮机叶片的质量检查提供借鉴。     

水环真空泵叶片安放角的计算

水环真空泵的诸参数对其性能有重要的影响。从水环真空泵的原理出发，通过水环流动善的分析，导出了叶片安放角的计算公式，并由试验结果得到了验证     

传动轴抗扭刚度的研究分析

本文根据电涡流比拟理论测试带键槽轴抗扭刚度和花键轴抗扭刚度的测试结果,分析比较了目前工程界沿用的几个 J_n 计算公式和实际应用精度,提出了它们抗扭刚度的经验公式,其精度在不超过实测值的5%范围内。     

Increasing flow efficiency of high-pressure and low-pressure steam turbine stages from numerical optimization of 3D blading

3D blading of a high-pressure and low-pressure steam turbine stage is optimized using Nelder–Mead method of deformed polyhedron. Values of the minimized objective function, i.e. stage losses with the exit energy are found from 3D viscous compressible flow computations, including turbulence effects. Among the optimized parameters are stator and rotor blade numbers and stagger angles, rotor blade twist angle, stator blade sweep and lean, both straight and compound. The blade sections (profiles) are assumed not to change during the optimization. There are constraints imposed on the design parameters, including the mass flow rate and stage reaction. Optimization gives designs with new 3D blade stacking lines, and with increased efficiencies, compared with the original design.     

In Situ Detection of Turbine Blade Vibration and Prevention

Turbine blades are the most critical components in any power plant. Failure in even one rogue blade out of hundreds of blades fixed on the rotor leads to colossal damage to the machine. Statistics have shown that low-pressure turbine blades in steam power plants are generally more susceptible to failure compared to high- or intermediate-pressure blades. The mechanism of failures is different in each case and is generally very complex. As a result, a large number of blade failures are not fully understood. Two primary forces acting on the blades are the steady centrifugal force due to rotation and the fluctuating steam bending force. In view of no direct access to monitor the health of the blades through vibration or other means, indirect method using non-contacting probes have been attempted and some are in use in special cases. Largely these methods are expensive and intrusive in nature. They involve placing of sensors in the narrow space inside the turbine casing, routing special signal cables with sealing arrangement and involves difficulties in analyzing shot duration signals from each rotating blades. Unless a diagnostic technique is made simple to implement and whose reliability is proven, power plants will not find it attractive to invest on upgrade for safe operation of the machine. This article is about an innovative method of detecting the presence of blade vibration in operating turbine through vibration signal analysis and prevention through process control. The method is based on vibration analysis of the turbine casing. The casing vibration includes signals associated with the blades of different stages called as blade passing frequency (BPF). When the rotating blades vibrate, the analysis of changes in the BPF is a novel way of diagnosing blade vibrations. Signals captured from operating plants have been analyzed and blade vibrations have been detected and verified with Campbell diagram. Laboratory experiments were carried out on a rotating fan to demonstrate robustness of the diagnostics tool for turbine blades.     

Vibration analysis for failure detection in low pressure steam turbine blades in nuclear power plant

This paper presents an investigation of the failure of a low-pressure steam turbine blade in a pressurized water reactor (PWR) nuclear power plant. The dynamical behaviour of the blade is analyzed theoretically and experimentally. A three-dimensional finite element model is used to predict the blade resonances in the operational speed range. Natural frequencies and mode shapes of the blade at static condition are obtained, then natural frequencies of the blade at different rotational speeds are calculated with consideration of centrifugal force and steam flow forces. A Campbell diagram is plotted to predict the likely operational conditions that may cause resonant vibration of the blade. Vibration tests are conducted to determine the vibration characteristic of the blade. It is found that the 2nd natural frequency of the blade is very close to the 9th rotor speed harmonic. The experimental natural frequencies are in good agreement with the finite element predicted values. Fretting wear is observed at the concave root surfaces of the blade trailing edge caused by resonant vibration. The fracture surface of the cracked blade shows typical fatigue patterns. The fretting wear characteristics in the crack initiation regions are observed.Stress distribution of the blade at the 9th harmonic frequency is analyzed using an elastic-plastic finite element model. Fretting fatigue experiments indicate that the fatigue life of the blade is greatly reduced due to fretting wear. The results of the investigation show that the failure of the blade is attributed to a combination of high cycle fatigue (HCF) and fretting wear.     

大型非线性转子-密封-轴承系统的不平衡响应与稳定性

对实际大型汽轮机转子-密封-轴承系统建立了具有超大规模维数的非线性动力学模型,该模型考虑了密封的非线性激振力、可倾瓦轴承的弹性支承力、转子的阻尼力、不平衡质量力和重力.采用Newmark方法对其进行数值求解,模拟出转子升速过程中汽流激振现象的典型特征和发生汽流激振的失稳转速,并且得到系统参数对转子不平衡响应和稳定性的影响规律.结果表明:适当的增大转子的阻尼、密封的半径间隙和密封流体轴向流速可提高转子发生汽流激振的失稳转速,这为在设计和运行中提高实际大型汽轮机转子-密封-轴承系统的稳定性提供了参考依据.     

变面积电涡流传感器带冠叶片振动测量

为实现对各种带冠叶片的振动的非接触式测量,提出一种基于变面积型电涡流传感器的带冠叶片振动测量技术。当转子叶片进行高速旋转时,叶片扫过电涡流传感器,会使感应面积发生变化,后接高速数据采集分析处理系统,将面积变化信号进行处理,从而获得带冠叶片振动参数。在某型汽轮机末级带冠叶片上进行振动试验,试验结果表明变面积型电涡流传感器测振技术可以在转子高速旋转的情况下,准确测量带冠叶片振动情况,得到振动的幅值和频率,可以应用在实际带冠叶片的振动测量中,为转子叶片健康状况评估提供依据。     

混流式水轮机转轮叶片流激振动分析

结合小变形弹性理论和不可压缩粘性流体的最大功率耗散原理构造流体-叶片系统的功率泛函,通过广义变分原理建立了混流式水轮机转轮叶片在非定常湍流场中考虑流体-结构相互作用(FSI)的有限元模型,计算叶片在FSI情况下的流激振动。数值计算采用分离迭代格式,流动用大涡模拟(LES),叶片振动用直接积分法。试验模型以某型水轮机为原型设计制作,在一片叶片的正面和负面上分别装有5只Kulite的压力传感器,在另一片叶片上装有3只微加速度传感器。计算得到的叶片自振频率、频谱曲线以及加速度时程与试验实测结果是吻合的。     

Fatigue life assessment of a low pressure steam turbine blade during transient resonant conditions using a probabilistic approach

This paper presents a sequential approach used in fatigue life prediction of a low pressure steam turbine blade during resonance conditions encountered during a turbine start-up by incorporating probabilistic principles. Material fatigue properties are determined through experimental testing of used blade material X22CrMoV12-1 along with statistical modelling using regression analysis to interpret the stress-life diagram. A finite element model of a free-standing LP blade is developed using the principle of sub-structuring which enables the vibration characteristics and transient stress response of the blade to be determined for variations in blade damping. Random curve fitting routines are performed on the fatigue and FEM stress data to ensure that the selection of the random variables used in fatigue life calculations is stochastic in nature. The random vectors are selected from a multivariate normal distribution. The use of confidence intervals in the probabilistic fatigue life model works effectively in being able to account for uncertainty in the material fatigue strength parameters and varying stress in the blade root. The predicted fatigue life of the blade is shown to be in good agreement with discrete life modelling results.     

风力机叶片挥舞摆振气弹失稳分析

为避免风机叶片在强风作用下发生破坏,需对其采取停机保护措施。该文研究叶片处于非旋转状态时的挥舞摆振气弹失稳现象发生的条件。基于风力机叶片简化模型,采用迭代法求解叶片的自振频率及振型,建立了非旋转叶片挥舞摆振气弹效应响应的振型叠加法,该方法可以便捷地进行叶片多工况气动弹性响应分析。计算了在不同风速不同攻角条件下叶片的挥舞摆振气弹效应响应,得到了叶片挥舞摆振响应随风速和风攻角的变化规律以及不稳定风攻角的分布特征。结果表明:在某些风攻角下,风机叶片挥舞摆振失稳现象在风速较低的情况就有可能发生,其响应幅值与结构阻尼联系紧密。另外,挥舞摆振失稳会大大增加作用于叶片上的风荷载,并进一步造成叶片结构的损伤破坏。     

多级离心泵流场优化及验证

流体激励力是离心泵主要振源之一。通过对离心泵流场进行优化,可有效降低泵组流体激励力,减小离心泵振动。以多级离心泵的减振降噪为研究目的,运用CFD仿真技术从切割叶轮及改变蜗壳形状两个方面对流场进行优化。通过对比优化前后压力脉动以及流场激励力变化,说明优化情况。最后考虑加工工艺要求,选择切割叶轮的优化方法,并通过机脚振动响应的变化间接验证改善效果。结果表明：切割叶轮与改变隔舌形状对离心泵叶频及其倍频下的压力脉动与流体激励力都有减小,切割叶轮后机脚响应降低了4 dB。     

基于时频滤波的汽轮机半速涡动故障成分提取

汽轮机油膜涡动是滑动轴承失稳而产生的自激振动,其振动频率主要表征为转子转频的一半或略小。当油膜涡动频率等于转子一阶临界转速时会导致振动加剧,进而对汽轮机的稳定运行产生严重影响。Gabor变换是一种可逆的联合时频分布方法,其逆变换具有时域信号重构的能力。基于Gabor变换对850 MW汽轮机振动信号进行时频分析,显示反映轴系不稳定的半速涡动成分,进一步对该成分进行时频带通滤波,并基于Gabor逆变换予以时间重构,获取半速涡动成分的峰峰值量化指标,为汽轮机轴承油膜涡动故障提供诊断依据。