Nonlinear Flap-Wise Vibration Characteristics ofWind Turbine Blades Based onMulti-Scale AnalysisMethod

This work presents a novel approach to achieve nonlinear vibration response based on the Hamilton principle.We chose the 5-MW reference wind turbine which was established by the National Renewable Energy Laboratory(NREL),to research the effects of the nonlinear flap-wise vibration characteristics.The turbine wheel is simplified by treating the blade of a wind turbine as an Euler-Bernoulli beam,and the nonlinear flap-wise vibration characteristics of the wind turbine blades are discussed based on the simplification first.Then,the blade’s large-deflection flap-wise vibration governing equation is established by considering the nonlinear term involving the centrifugal force.Lastly,it is truncated by the Galerkin method and analyzed semi-analytically using the multi-scale analysis method,and numerical simulations are carried out to compare the simulation results of finite elements with the numerical simulation results using Campbell diagram analysis of blade vibration.The results indicated that the rotational speed of the impeller has a significant impact on blade vibration.When the wheel speed of 12.1 rpm and excitation amplitude of 1.23 the maximum displacement amplitude of the blade has increased from 0.72 to 3.16.From the amplitude-frequency curve,it can be seen that the multi-peak characteristic of blade amplitude frequency is under centrifugal nonlinearity.Closed phase trajectories in blade nonlinear vibration,exhibiting periodic motion characteristics,are found through phase diagrams and Poincare section diagrams.

Present Status and Prospect of High-Frequency Electro-hydraulic Vibration Control Technology

Electro-hydraulic vibration equipment(EHVE)is widely used in vibration environment simulation tests,such as vehicles,weapons,ships,aerospace,nuclear industries and seismic waves replication,etc.,due to its large output power,displacement and thrust,as well as good workload adaptation and multi-controllable parameters.Based on the domestic and overseas development of high-frequency EHVE,dividing them into servo-valve controlled vibration equipment and rotary-valve controlled vibration equipment.The research status and progress of high-frequency electro-hydraulic vibration control technology(EHVCT)are discussed,from the perspective of vibration waveform control and vibration controller.The problems of current electro-hydraulic vibration system bandwidth and waveform distortion control,stability control,offset control and complex vibration waveform generation in high-frequency vibration conditions are pointed out.Combining the existing rotary-valve controlled high-frequency electro-hydraulic vibration method,a new twin-valve independently controlled high-frequency electro-hydraulic vibration method is proposed to break through the limitations of current electro-hydraulic vibration technology in terms of system frequency bandwidth and waveform distortion.The new method can realize independent adjustment and control of vibration waveform frequency,amplitude and offset under high-frequency vibration conditions,and provide a new idea for accurate simulation of high-frequency vibration waveform.

Vertical vibration control using nonlinear energy sink with inertial amplifier

To reduce additional mass, this work proposes a nonlinear energy sink(NES)with an inertial amplifier(NES-IA) to control the vertical vibration of the objects under harmonic and shock excitations. Moreover, this paper constructs pure nonlinear stiffness without neglecting the gravity effect of the oscillator. Both analytical and numerical methods are used to evaluate the performance of the NES-IA. The research findings indicate that even if the actual mass is 1% of the main oscillator, the NES-IA with proper inertia angles and mass distribution ratios can still effectively attenuate the steady-state and transient responses of the main oscillator. Nonlinear stiffness and damping also have important effects. Due to strongly nonlinear factors, the coupled system may exhibit higher branch responses under harmonic excitation. In shock excitation environment, the NES-IA with a large dynamic mass can trigger energy capture of both main resonance and high-frequency resonance. Furthermore, the comparison with the traditional NES also confirms the advantages of the NES-IA in overcoming mass dependence.

Time-dependent Vibration Frequency Reliability Analysis of Blade Vibration of Compressor Wheel of Turbocharger for Vehicle Application

Blade vibration failure is one of the main failure modes of compressor wheel of turbocharger for vehicle application.The existing models for evaluating the reliability of blade vibration of compressor wheel are static,and can not reflect the relationship between the reliability of compressor wheel with blade vibration failure mode and the life parameter.For the blade vibration failure mode of compressor wheel of turbocharger,the reliability evaluation method is studied.Taking a compressor wheel of turbocharger for vehicle application as an example,the blade vibration characteristics and how they change with the operating parameters of turbocharger are analyzed.The failure criterion for blade vibration mode of compressor wheel is built with the Campbell diagram,and taking the effect of the dispersity of blade natural vibration frequency and randomness of turbocharger operating speed into account,time-dependent reliability models of compressor wheel with blade vibration failure mode are derived,which embody the parameters of blade natural vibration frequency,turbocharger operating speed,the blade number of compressor wheel,life index and minimum number of resonance,etc.Finally,the rule governing the reliability and failure rate of compressor wheel and the method for determining the reliable life of compressor with blade vibration is presented.A method is proposed to evaluate the reliability of compressor wheel with blade vibration failure mode time-dependently.

Vibration reliability analysis for aeroengine compressor blade based on support vector machine response surface method

To ameliorate reliability analysis efficiency for aeroengine components, such as compressor blade, support vector machine response surface method(SRSM) is proposed. SRSM integrates the advantages of support vector machine(SVM) and traditional response surface method(RSM), and utilizes experimental samples to construct a suitable response surface function(RSF) to replace the complicated and abstract finite element model. Moreover, the randomness of material parameters, structural dimension and operating condition are considered during extracting data so that the response surface function is more agreeable to the practical model. The results indicate that based on the same experimental data, SRSM has come closer than RSM reliability to approximating Monte Carlo method(MCM); while SRSM(17.296 s) needs far less running time than MCM(10958 s) and RSM(9840 s). Therefore,under the same simulation conditions, SRSM has the largest analysis efficiency, and can be considered a feasible and valid method to analyze structural reliability.

A Comparative Study of Bayes Classifiers for Blade Fault Diagnosis in Wind Turbines through Vibration Signals

Renewable energy sources are considered much in energy fields because of thecontemporary energy calamities. Among the important alternatives being considered, windenergy is a durable competitor because of its dependability due to the development of theinnovations, comparative cost effectiveness and great framework. To yield wind energymore proficiently, the structure of wind turbines has turned out to be substantially bigger,creating conservation and renovation works troublesome. Due to various ecologicalconditions, wind turbine blades are subjected to vibration and it leads to failure. If thefailure is not diagnosed early, it will lead to catastrophic damage to the framework. In orderto increase safety observations, to reduce down time, to bring down the recurrence ofunexpected breakdowns and related enormous maintenance, logistic expenditures and tocontribute steady power generation, the wind turbine blade must be monitored now andthen to assure that they are in good condition. In this paper, a three bladed wind turbinewas preferred and using vibration source, the condition of a wind turbine blade is examined.The faults like blade crack, erosion, hub-blade loose connection, pitch angle twist and bladebend faults were considered and these faults are classified using Bayes Net (BN),Discriminative Multinomial Naïve Bayes (DMNB), Naïve Bayes (NB), Simple NaïveBayes (SNB), and Updateable Naïve Bayes (UNB) classifiers. These classifiers arecompared and better classifier is suggested for condition monitoring of wind turbine blades.

Vibration-Based Analysis for Detecting Turbocharger Blade Defect on High-Power Diesel Generator

This study is concerned with 12-MW capacity turbochargers on diesel power generators. These are generators equipped with 18 cylinders. Our previous studies [1] showed that the processing of vibration signature collected from a power generator is very complex, insomuch the dominant vibration remains the one originating from explosion frequency in the diesel generator cylinders, with a fairly high number of cylinders. This vibration drowns out all other possible vibrations, which can expose defects. The study at hand is focused on turbochargers with 20,940 rpm, while the rotation speed in the diesel engine is 600 rpm only. With the turbocharger rotating at very high speed, it results in severe mechanical constraints on the rotor shaft in the turbocharger and its related organs (turbine blades). The wear of turbine blades can result in breakdowns in the turbocharger. This article is an attempt to early detect defaults in turbine blades based on vibration signature that can be experimentally determined. We noted in our investigations that a diesel engine and its turbochargers do not bear the same mechanic loads. While the diesel engine is the seat of violent shocks brought about by explosions in cylinders, the turbochargers are driven by the action of exhaust gas from explosions, without being affected by explosion shocks. The study found that explosion frequency in the diesel engine cylinders, which disrupted the vibration signals in the diesel engine and alternator, did not impact on the vibration signals in the turbocharger. We experimentally determined, following several campaigns of measurements, a vibration signature on the turbochargers under study, which corresponds to a defect in turbine blades.

Vibration Characteristics of Mistuned Bladed Disks

The finite element models of blade, disk and bladed disk are built up by finite element software ANSYS. The natural frequencies of the single blade, the whole bladed disk and the bladed disk with only one sector by cyclic symmetry boundary have been calculated. Then, based on the results above, a structure dynamic model of multiple degree-of-freedom (MDOF) systems is established to simulate the bladed-disk assembly. Solve the motion equation by using the Runge-Kutta Method (Gill Method). The dynamic response of the MDOF system is achieved. As for the given mistuning patterns, the vibration responses of bladed disks are calculated. The results have been compared and analyzed, and the optimum pattern is selected.

Vibration Modal Analysis of Compressor Blade based on ANSYS

Compressor is an important part of aero engine. In the environment of high temperature and high pressure,compressor blade will suffer from several physical and chemical processes,such as centrifugal force,aerodynamic force vibration and oxidation. These processes will lead compressor blade to fatigue fracture,and at the same time,make negative effects on the engine' s overall performance. Based on the software ANSYS15. 0,we made strength analysis and modal analysis of compressor blade in this paper. As a result,we got its natural frequencies,relevant modal parameters and vibration mode cloud pictures. After analyzing the influence that centrifugal force made on modal parameters,we predicted the expected damage of the blade. Eventually the analysis results will provide the basis for overall performance evaluation,structural crack detection,fatigue life estimation and strength calculation of aircraft engine compressor.

Dynamic Response Analysis of A 5 MW NREL Wind Turbine Blade under Flap-Wise and Edge-Wise Vibrations

A wind turbine is subjected to a regime of varying loads.For example,each rotor revolution causes a complete gravity stress reversal in the low-speed shaft,and there are varying stresses from the out-of-plane loading cycle due to fluctuating wind load.Consequently,wind turbine blade design is governed by fatigue rather than ultimate load considerations.Previous studies have adopted many different beam theories,using different techniques and codes,to model the National Renewable Energy Laboratory(NREL)5MWoffshore wind turbine blade.There are differences,from study to study,in the free vibration results and the dynamic response.The contribution of this study is to apply the code written by the authors to the different beam theories used with the aim of comparing the different beam theories presented in the literature and that developed by the authors.This paper reports the investigation of the effects of deformation parameters on the dynamic characteristics of the NREL 5 MW offshore wind turbine blades predicted by the different beam theories.The investigation of free vibrations is a fundamental step in the analysis of structural dynamics,and this study compares different computational structural methods and investigates their effect on the predicted dynamic response.The modal characteristics of every model examined have been combined with strip theory to determine the dynamic response of the blade.

Experimental and Numerical Investigation of Non-synchronous Blade Vibration Excitation in a Transonic Axial Compressor

The complex flow phenomenon of rotating instability(RI) and its induced non-synchronous vibration(NSV) have become a significant challenge as they continuously increase aerodynamic load.This study aims to provide an understanding of the non-synchronous blade vibration phenomenon caused by the rotating instability of a transonic axial compressor rotor.In this case,blade vibrations and non-synchronous excitation are captured by strain gauges and unsteady wall pressure transducer sensors.Unsteady numerical simulations for a full-annulus configuration are used to obtain the non-synchronous flow excitation.The results show that the first-stage rotor blade exhibits an NSV close to the first bending mode;NSV is accompanied by a sharp increase in pressure pulsation;amplitude can reach 20%,and unsteady aerodynamic frequency will lock in a structural mode frequency when the blade vibrates in a large-amplitude motion.The predicted NSV frequency aligns well with the experimental results.The dominant mode of circumferential instability flow structure is approximately 47% of the number blades,and the cell size occupies 2-3 pitches in the circumferential direction.The full-annulus unsteady simulations demonstrate that the streamwise oscillation of the shedding and reattachment vortex structure is the main cause of NSV owing to the strong interaction between the tip leakage and separation vortices near the suction surface.

Cavitation Detection in Variable Speed Pump by Analyzing the Acoustic and Vibration Spectrums

Cavitation in pumps must be detected and prevented. The present work is an attempt to use the simultaneous measurements of vibration and sound for variable speed pump to detect cavitation. It is an attempt to declare the relationship between the vibration and sound for the same discharge of 780 L/h and NPSHA of 0.754 at variable speeds of 1476 rpm, 1644 rpm, 1932 rpm, 2190 rpm, 2466 rpm, and 2682 rpm. Results showed that: the occurrence of cavitation depends on the rotational speed, and the sound signals in both no cavitation and cavitation conditions appear in random manner. While, surveying the vibration and sound spectrums at the second, third, and fourth blade passing frequencies reveals no indications or phenomenon associated with the cavitation at variable speeds. It is recommended to survey the vibration spectra at the rotational and blade passing frequencies simultaneously as a detection unique method of cavitation.

基于包络分析的汽轮机叶片振动监测信号处理方法

以汽轮机末级叶片为研究对象,使用末级叶片径向围带上方的传感器采集叶片振动信号,针对信号波动较大,难以确定每支叶片通过传感器位置时刻的问题,采用时域信号的处理方法来确定触发时刻。对信号使用两层Hampel滤波器来消除信号的野点;对处理完的数据进行重采样,消除小范围的波动量;使用平滑滤波来处理数据,使得信号在局部具有单调性;求取信号的包络线,将包络线乘以系数作为信号的触发门限。相对于频域滤波方法,该方法较好地保持了信号的形状,能够精确地识别叶片通过传感器的时刻,对于波动大的信号尤其适用。

基于流固耦合的压气机转子叶片非同步振动分析

压气机转子叶片非同步振动是近年来发现的一类新气动弹性问题,表现为叶片振动频率与转频不同步且具有锁频现象,严重影响航空发动机的可靠性和运行安全,目前对其产生机理并不完全清楚.为了深入研究压气机内不稳定流动与叶片非同步振动之间的耦合机制,基于时间推进的方法建立了多级压气机转子叶片全环的双向流固耦合模型,数值研究了刚性叶片与非同步振动柔性叶片的非定常流场、气流激励频率和结构响应特征,揭示了压气机转子叶片非同步振动的流固耦合机制.结果表明:近失速工况下,转子叶尖吸力面径向分离涡的周期性脱落及再附过程是导致叶尖压力剧烈波动的主要原因,其3倍谐波激励频率与转子一阶弯曲固有频率接近,提供了叶片非同步振动的初始气流激励源.叶片非同步振动发生时,位移响应表现为等幅值的极限环特征,振动以一阶弯曲模态主导,径向分离涡产生的非整数倍气流激励频率及其谐波频率最终锁定为叶片一阶弯曲固有频率,非同步振动的运动胁迫使得相邻通道叶尖流场周向趋于一致.研究成果及对叶片非同步振动流固耦合机制的认识可为压气机内部不稳定流动诱发的叶片振动失效分析提供有益参考.

航发叶片类零件振动回转抛磨的磨损行为分析

振动抛磨已应用于航空发动机叶片抛光,该工艺仍存在加工效率低、均匀一致性差的问题。针对这些问题,基于离散元法和滚磨光整加工理论,提出了航空发动机叶片类零件振动回转抛磨工艺方案。采用EDEM模拟分析了工件表面磨损深度随时间的变化规律,并探究了工件埋入深度、滚筒大小(直径、长度)对加工效果的影响。结果表明:相对于传统的振动抛磨,振动回转抛磨能改变工件在颗粒介质流场中的空间位置,有利于提高工件表面加工一致性;当工件在回转过程中的空间位置沿径向变化较小时,即工件位于滚筒轴心位置,工件的加工效果较好;通过改变滚筒大小,可以改善工件的加工效果,综合考虑工件表面加工效率及均匀一致性,根据仿真结果选取滚筒大小最佳参数范围:滚筒直径:(90~100)mm,滚筒长度:(80~100)mm。

转子叶盘结构减振方法研究

转子叶盘结构在高速和超高速的运行状况下,可能因为失稳而剧烈振动,进而引发严重的安全事故。增大叶盘结构阻尼是减轻其振动的有效方法之一。国内外学者针对叶盘结构,开展了大量的研究,为了充分了解叶盘结构减振方法的研究进展,推动相关问题的深入研究,提出了将叶盘结构减振分为干摩擦、内摩擦和其他能量转换方式。对叶盘结构减振方法的相关研究进展进行了总结,并展望了叶盘结构减振的未来研究方向。

基于数字图像处理技术的叶片结构模型构建

为了研究图像法代替传统标准四层振筛法建立烟叶叶片结构特征面积阈值模型,离线扫描了每片舒展的烟叶图像,经B分量指标阈值、腐蚀膨胀闭运算后剔除背景并提取了完整的烟叶图像,通过8-邻域提取法计算了每片烟叶像素面积并进行排序,每间隔1个点遍历像素面积区间所有点,与实际大片、中片、小片、碎片率进行对比,选择不同面积阈值下预测误差最小的像素面积值即为大片、中片、小片、碎片率组成的面积特征阈值模型,并对模型进行了外部验证和重复性检测。结果表明,叶片结构组成为[+∞,50880]、(50880,17230]、(17230,2380]、(2380,0]的面积特征区间模型,通过外部验证与标准四层振筛对比,大片、中片、小片、碎片率误差分别为1.09%、0.64%、0.47%、1.07%;图像法重复性检测的大片、中片、小片、碎片率标准偏差分别为0.88%、0.84%、0.19%、0.26%。由此可知,图像法建立的叶片结构模型稳定性较好并且能够很好地预测烟叶的大片、中片、小片、碎片率。

5种规格金刚石圆锯片的行波振动分析及优化

为降低金刚石圆锯片在石材切割时产生的锯切噪声,选取常规锯片、打孔锯片、切缝锯片以及在基体上开鼻型径向槽、开孔与夹层的5种典型金刚石圆锯片,利用Workbench软件对其模态、行波振动进行分析,研究其对行波振动的影响。结果表明:直径为180和230 mm的常规锯片出现行波共振,产生强烈噪声;直径为105、115和350 mm的常规锯片不出现行波共振。直径为180和230 mm的切缝锯片δ值偏大,有效避开了行波共振;直径为115和350 mm的切缝锯片δ值偏小,其降噪效果差;而直径为105 mm的夹层锯片δ值偏大,降噪效果好。5种直径锯片采用开鼻形径向槽、雨滴孔和阻尼夹层的设计方案,其δ值分别为8.13%、7.21%、6.01%、6.39%和7.00%,可进一步避开行波共振,其降噪效果更好。

基于单高速相机3D-DIC的涡轮叶片全场振动测量

采用成本较低、结构紧凑且使用便捷的单高速相机三维数字图像相关方法(single-camera high-speed three-dimensional digital image correlation,简称SCHS 3D-DIC)对涡轮叶片的振动特性进行试验研究。首先,介绍了测量装置和原理,以悬臂铝板为对象开展验证试验,结果证明了该测量系统的准确性与有效性;其次,开展了叶片的全场振动特性测量,得到了其三维形貌、模态特性、全场位移与应变分布,获得了叶片在振动载荷作用下的高应变区域位置及应变分布特点。研究表明,SCHS 3D-DIC方法相比常规双高速相机3D-DIC方法具有更高的视场利用率,适合于细长型的涡轮叶片的振动测量试验。

Solid particle size characterization by a high-frequency collision response in pneumatic particulate flow

A novel triaxial vibration method is developed for the real-time characterization of the solid particle size distribution(PsD)in pneumatic particulate flow,which is critical for chemical industry.In this work,the particle-wall collision and friction behaviours were analysed by the time-domain statistical and timefrequency joint methods to narrow the high-frequency response range by the initial experiment of free fall for a single particle,interparticle,and multiple particles.Subsequently,verification experiments of PSD characterization in pneumatic flow were performed.First,the quantitative triaxial energy response model that considers the particle size,shape,and mass factors were established.Second,a good agreement of the particle number identification was found between the triaxial vibration energy and mean particle size of 150-550μm.Moreover,the performance with the best accuracy was focused on a range of 42-43 kHz in the x-axis and z-axis and 36.8-38.8 kHz in the y-axis.Finally,the individual particle energy was inversely analysed by the triaxial vibration response within the optimized frequency bands,and the PSD was characterized in real-time by a low error rate,that is,5.2% from the XZ-axis direction of sand(42-43 kHz)and 5.6% from the XYZ-axis of glass(30.9-33.9 kHz,46.2-47.2 kHz,38.3-41.3 kHz for each axis response).Therefore,this research complements the existing approaches for PsD characterization in particulate multiphase flow.