Download or read book Vibration Analysis of Grouped Turbine Blades written by Laurence Floyd Wagner and published by . This book was released on 1993 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbomachine Blade Vibration written by J. S. Rao and published by New Age International. This book was released on 1991 with total page 466 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue Failures Of Blades Is One Of The Most Vexing Problems Of Turbomachine Manufacturers, Ever Since The Steam Turbine Became The Main Stay For Power Generating Equipment And Gas Turbines Are Increasingly Used In The Air Transport. The Problem Is Very Complex, Involving The Excitation Due To Aerodynamic Stage Interaction; Damping Due To Material Deformation, Friction At Slip Surfaces And Aerodynamic Damping; Vibration Of An Asymmetric Aerofoil Tapered Along Its Length And Mounted On A Rotating Disc At A Stagger Angle. The Problem Is Also Governed By Heat Transfer Analysis And Thermal Stresses.His Book Deals With A Basic Understanding Of Free Vibratory Behaviour Of Turbine Blades- Free Standing, Packetted, And Bladed-Discs. The Analysis Is Based On Continuous And Discrete Models Using Energy Principles And Finite Element Techniques. A Clear Understanding Of The Interference Phenomenon In A Thin Cambered Airfoil Stage In Subsonic Flow Is Presented To Determine The Nonsteady Excitation Forces Acting On The Blades. A Comprehensive Treatment On The Blade Damping Phenomenon That Occurs In Turbines Is Given. The Nonlinear Damping Models Account For Material Damping And Friction Damping As A Function Of Rotational Speed For Each Mode. Resonant Response Calculation Procedures For The Steadily Running As Well As Accelerating Blades Are Given.Cumulative Damage Calculations Are Then Outlined For Fatigue Life Estimation Of Turbomachine Blades. The Book Also Deals With Heat Transfer Analysis And Thermal Stress Calculations Which Help In A Comprehensive Understanding Of The Blade Problems.

Download or read book Vibration Analysis of Rotating Turbine Blades written by P. Trompette and published by . This book was released on 1974 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presented at the ASME Winter Annual Meeting, New York, N.Y., Nov. 17-22, 1974.

Download or read book Vibration Analysis of Turbine Blades Shell Structures with Isoparametric Finite Elements written by Mak, S. W. and published by Longueuil, Que[bec] : United Aircraft of Canada. This book was released on 1974 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Free Vibration Analysis of Twisted Non rotating Turbine Blades written by Curt R. Bilby and published by . This book was released on 1984 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanics and Vibration Modeling of Vertical axis Wind turbine Blades and Analysis of Systems with Parametric Excitation written by Fatemeh Afzali and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wind turbines are one of the fastest-growing energy sources. Based on their axis of rotation they fall into two basic categories: horizontal-axis wind turbines (HAWTs) and vertical-axis wind turbines (VAWTs). Darrieus VAWTs exploit aerodynamic lift. This study entails the vibration analysis of large vertical-axis Darrieus wind turbine blades. Very large wind turbines are becoming more abundant due to their ability to harvest greater wind power. VAWTs are less common than HAWTs for large wind applications, but have some favorable characteristics, for example in offshore applications, and so further development of large VAWTs is anticipated. However, VAWTs are known to have vibration issues. VAWT blade vibration is the focus of this work.The straight-bladed H-rotor/Giromill is the simplest type of VAWT. We first derive the equations of motion of a H-rotor blade modeled as a uniform straight elastic Euler-Bernoulli beam under transverse bending and twist deformation. The reduced-order model suggests the existence of periodic damping, periodic stiffness, and direct excitation generated by a cyclic aeroelastic load. The model also indicates spin softening, which could be detrimental as the turbines become large. Periodic damping and stiffness are examples of parametric excitation and are likely to carry over to other types of VAWT blades. Systems with parametric excitation have been studied with various methods. Floquet theory has been classically used to study the stability characteristics of linear systems with periodic coefficients, and has been commonly applied to Mathieu's equation, which represents a vibration system with periodic stiffness. We apply the Floquet theory combined with the harmonic-balance method to a linear vibration system with a periodic damping coefficient. Based on this theory, the approximated solution includes an exponential part, with an unknown exponent, and a periodic part. Our analysis investigates the initial conditions response, the boundaries of instability, and the characteristics of free response solution of the system. The coexistence phenomenon, in which some of the transition curves overlap so that the instability wedges disappear, is recovered in this approach, and is examined closely.An additional case of the parametric excitation is the combination of parametric damping and parametric stiffness. The Floquet-based analysis shows that the combined parametric excitation reshapes the stability characteristics, compared to the system with only parametric damping or stiffness and disrupts the coexistence which is observed in the parametric damping case.The aeroelastic forces encountered by the wind turbines can cause self-excitation in blades, the mechanism of which can be loosely modeled with van-der-Pol-type nonlinearity. We seek to understand the combined effect of parametric excitation and van der Pol nonlinearity, as both can induce instabilities and oscillations. The oscillator is studied under nonresonant conditions and secondary resonances, with and without external excitation. We analyze the system using the method of multiple scales and numerical solutions. For the case without external excitation, the analysis reveals nonresonant phase drift (quasi-periodic responses), and subharmonic resonance with possible phase drift or phase locking (periodic responses). Hard excitation is treated for nonresonant conditions and secondary resonances, and similar phenomena are uncovered.Some Darrieus VAWTs consist of curved blades. We lastly study the modal analysis of curved Darrieus wind-turbine blades and obtain the mode shapes and modal frequencies. The governing equations are derived using the fundamental deformation mechanics, and thin beam approximations are employed to express the strain and kinetic energies. The assumed-modes method is applied to the energies, and the Euler-Lagrange equation is used to discretize the equations of motion. Implementing these equations, mode shapes are calculated and mapped back onto the curved beam for visualization. This analysis is conducted for pinned-pinned and hinged-hinged blades. The results are compared with Finite element analysis using Abaqus and with the literature.

Download or read book Vibration Analysis of Cracked Turbine and Compressor Blades written by Wiesław M. Ostachowicz and published by . This book was released on 1990 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The object of the paper is to present a method of vibration analysis of cracked turbine and compressor blades. A transverse crack in a blade introduces local flexibility, which changes dynamic characteristics of a structure. The assumption of the open and closed crack leads to a model with point finite elements which are introduced to the crack model. The blade is modelled by spatial finite elements. The method described in the paper can be used for the study of the effects of crack locations and sizes on the vibrational behavior of the structure. The analysis is provided along with an algorithm and an example of calculations. The authors have compared the calculation results of the beam model with a crack (regardless of friction in the crack) with the investigation results of paper [2] and have succeeded in obtaining a high compatibility of the results. However, the comparison of the results relevant to the model taking into account friction in the crack was impossible due to unavailability of similar papers in literature.

Download or read book The Shock and Vibration Digest written by and published by . This book was released on 1983 with total page 600 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Structural Analysis of Composite Wind Turbine Blades written by Dimitris I Chortis and published by Springer. This book was released on 2015-08-07 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book concerns the development of novel finite elements for the structural analysis of composite beams and blades. The introduction of material damping is also an important aspect of composite structures and it is presented here in terms of their static and dynamic behavior. The book thoroughly presents a new shear beam finite element, which entails new blade section mechanics, capable of predicting structural blade coupling due to composite coupling and/or internal section geometry. Theoretical background is further expanded towards the inclusion of nonlinear structural blade models and damping mechanics for composite structures. The models effectively include geometrically nonlinear terms due to large displacements and rotations, improve the modeling accuracy of very large flexible blades, and enable the modeling of rotational stiffening and buckling, as well as, nonlinear structural coupling. Validation simulations on specimen level study the geometric nonlinearities effect on the modal frequencies and damping values of composite strips of various angle-ply laminations under either tensile or buckling loading. A series of correlation cases between numerical predictions and experimental measurements give credence to the developed nonlinear beam finite element models and underline the essential role of new nonlinear damping and stiffness terms.

Download or read book The Shock and Vibration Digest written by and published by . This book was released on 1996 with total page 624 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fatigue Life Estimation of Turbine Blades Due to Transient Thermal Vibratory and Centrifugal Stresses written by Deepak Dhar and published by . This book was released on 1994 with total page 498 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Vibration Based Condition Monitoring of Wind Turbines written by Tomasz Barszcz and published by Springer. This book was released on 2018-12-04 with total page 233 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes in detail different types of vibration signals and the signal processing methods, including signal resampling and signal envelope, used for condition monitoring of drivetrains. A special emphasis is placed on wind turbines and on the fact that they work in highly varying operational conditions. The core of the book is devoted to cutting-edge methods used to validate and process vibration data in these conditions. Key case studies, where advanced signal processing methods are used to detect failures of gearboxes and bearings of wind turbines, are described and discussed in detail. Vibration sensors, SCADA (Supervisory Control and Data Acquisition), portable data analyzers and online condition monitoring systems, are also covered. This book offers a timely guide to both researchers and professionals working with wind turbines (but also other machines), and to graduate students willing to extend their knowledge in the field of vibration analysis.

Download or read book Dynamics With Friction Modeling Analysis And Experiment Part I written by Ardeshir Guran and published by World Scientific. This book was released on 1996-08-23 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt: The dynamics of dissipative mechanical and structural systems is being investigated at various institutions and laboratories worldwide with ever-increasing sophistication of modeling, analysis and experiments. This book offers a collection of contributions from these research centers that represent the state-of-the-art in the study of friction oscillators. It provides the reader with the fruits of a team effort by leaders in this fascinating field.The topics covered include friction modeling, self-excited friction oscillators, homogeneous frictional systems, unsteady lubricated friction, instantaneous contact geometry, impact damping, friction-induced instability and nonlinear dynamics of stick-slip systems, among other topics.This book gives a comprehensive picture of dynamics of dissipative mechanical and structural systems. It also gives an up-to-date account of the present state of the field. It will be of interest to engineers, rheologists, material scientists, applied mathematicians, physicists and historians of science and technology.

Download or read book Vibration Analysis and Optimisation of a Wind Turbine Blade written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Vibration of Grouped Turbine Buckets a Finite Element Technique written by Albert Craig Stickler and published by . This book was released on 1971 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbine Blade Vibration Analysis written by Dokku Srinivasa Rao and published by . This book was released on 2018-09-26 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Feasibility of Vibration based Damage Detection for Pinned Turbine Blades written by Leon Brits and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbine blades are subjected to various damage mechanisms with fatigue as the primary contributor. During operation, damage accumulates in the form of crack initiation and propagation. This may lead to catastrophic failure, which is cause for concern in terms of availability and safety of the turbine. To optimize the maintenance schedule and to provide operational exibility of the turbine, the state of health of the blades is monitored. This is usually accomplished through non-destructive testing (NDT) during outages. Conventional NDT techniques for in-situ inspection of turbine blade and disk assemblies is di cult and often ine ective, due to limited access to areas of concern, as well as the complex geometries of blade roots. O -site inspection can be costly if the blades are still assembled in the turbine disk since the process of removing and reinstalling these blades is critical and labour-intensive, increasing the turbine downtime and overall costs. These problems could potentially be overcome by employing inspection techniques that o er the prospect of assessing obstructed areas through monitoring the global dynamic characteristics of the structure, which provide relatively easily interpretable data. With global inspection methods, a degree of measurement sensitivity is forfeited but the potential to detect more severe damage, without prior knowledge of the precise damage area location, exists. In this dissertation, the feasibility of a vibration-based structural damage identi cation technique that could be usable in support of conventional NDT to detect cracks in pinned turbine blades during o -line in-situ inspection, is evaluated. The investigation was limited to considering uninstalled single blades only, and thus o -site inspection of this component is regarded above the turbine disk assembly. This is clearly a simpli ed case and does not address the critical case from a practical perspective of having a large number of blades mounted onto a disk with pins, which is really the circumstance under which the technique could become useful. This study must thus be considered as a rst step towards addressing the real practical problem. In this simpli ed problem, the following questions are answered: Is it possible to detect damage in an unconstrained and isolated blade using vibration response, and if so, can di erent damage scenarios be identi ed? The proposed vibration-based damage detection method entails a multi-class support vector machine classi cation procedure in which the natural frequencies are employed as the discriminatory feature for damage detection and identi cation of di erent single-location damage scenarios. The natural frequencies were acquired from accurate experimental modal analysis of freely supported individual pinned turbine blades through impact testing. To con rm and predict the expected behaviour of the blades, a healthy numerical model was built and validated whereafter defects and damage were introduced. This includes geometrical variability at the root, observed in the procured blades, and the anticipated worstcase single-location damage at the most probable locations near or on the root, obtained from literature and discussions with experts in the industry. Arti cial damage, i.e. a uniform 1mm notch, was introduced in the root at the upper pinhole on the leading edge pressure side; and just above the root at the aerofoil base on the trailing- and the leading edge. To establish the discriminative quality of the modal property natural frequency, it was necessary to determine its sensitivity to geometrical variability and damage. It was also required to establish the damage-speci c behaviour or damage trend in the experimental data of i Executive Summary Feasibility of Vibration-based Damage Detection for Pinned Turbine Blades these damage scenarios to conclude their distinctiveness. This analysis was extended to outlining the feature quality by exploring the separability of class clusters for the healthy and damage scenario(s). The feasibility of the proposed method is assessed using experimental data through simple hypothesis testing regarding the detection and identi cation of both geometrical variability in healthy blades, and damage. It was found that healthy blades are very similar, as geometrical variability cannot be detected. This is because the distributions of natural frequencies fall within a range about a mean value in an ambiguous cluster. In contrast to this, the damage scenarios were found to be distinct, and thus discernible from the healthy blades. These classes formed discrete clusters, each with a similar distribution than the healthy blades. The conclusion of the feasibility study serves as proof of concept.