Volume 7C: Structures and Dynamics最新文献

{"title":"Vibration Analysis From Simulated Tip Timing Sensor Signal Shape Modulation","authors":"D. Heller, I. A. Sever, C. Schwingshackl","doi":"10.1115/GT2018-75010","DOIUrl":"https://doi.org/10.1115/GT2018-75010","url":null,"abstract":"Blade Tip Timing (BTT) enables non-contact and non-intrusive measurements of the vibrational behaviour of rotating blades. The classical tip timing technology is based on arrival times when blades pass sensors mounted around the casing. Various post-processing methods have been proposed in the literature to extract the vibration behaviour of the bladed disk from arrival time data. However, the accuracy of these methods to determine vibration and modal parameters suffers from inherent under-sampling of BTT. Novel solutions are needed to extend BTT capabilities to non-linear and multi-mode vibration analysis. In this paper, an alternative approach to the signal processing of BTT sensor data is presented, focusing on the actual sensor signal shape data. The approach is based on the assumption that the vibration of blades leads to a certain modulation of the sensor output. Comparing this modulation with one from a non-vibrating condition, it is possible to extract vibration information. In this numerical study, a virtual capacitance sensor and bladed disk model is introduced to simulate the sensors with adjustable signal shape functions and to generate signal shapes from passing blades for three test cases. Data processing techniques are used to extract relevant vibration data from simulated signal shapes. It could be shown that the sensor signal shapes are modulated differently depending on the vibrational state of a passing blade. Parameters such as the blade tip dimension, sensor field characteristics, excitation, rotational speed, amplitude and frequency of vibration have a discernible effect on the sensor signal shapes.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124026346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stress Calibration Methodology of Stator Blades Using Experimental SAFE Diagram","authors":"J. Ligot, Sébastien Hoffait, Jean de Cazenove, F. Vallino, J. Golinval","doi":"10.1115/GT2018-76709","DOIUrl":"https://doi.org/10.1115/GT2018-76709","url":null,"abstract":"This paper introduces an improvement of the stress calibration methodology of stator blades to consider a nodal diameter of interest of the structure. The proposed calibration procedure and the search for optimal excitation set-up are detailed. To this purpose, the following points are addressed.\u0000 Experimental modal analyses are performed using both accelerometers and strain gages. Post-processing techniques are developed to determine the nodal diameters of the identified modes. SAFE (Singh’s Advanced Frequency Evaluation) diagrams are computed from the experimental data and compared with the diagrams obtained numerically by finite elements computations.\u0000 Multiple excitations are used to appropriate the targeted modes. A comparative study of different shaker types, of the number of excitation points and of their location is performed.\u0000 Calibration is achieved by comparing strain measurements taken on one gage installed on the engine and velocities measured using laser vibrometers. It allows reducing the impact of the instrumentation on the modal content.\u0000 The calibration factors obtained by the novel proposed procedure are compared to the ones given by the currently used methodology.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131015507","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Conceptual Flutter Analysis of Labyrinth Seals Using Analytical Models: Part I — Theoretical Support","authors":"R. Corral, A. Vega","doi":"10.1115/GT2018-75958","DOIUrl":"https://doi.org/10.1115/GT2018-75958","url":null,"abstract":"A simple non-dimensional model to describe the flutter onset of labyrinth seals is presented. The linearized equations for a control volume which represents the inter-fin seal cavity, retaining the circumferential unsteady flow perturbations created by the seal vibration, are used. Firstly, the downstream fin is assumed to be choked, whereas in a second step the model is generalized for unchocked exit conditions. An analytical expression for the non-dimensional work-per-cycle is derived. It is concluded that the stability of a two-fin seal, depends on three non-dimensional parameters, which allow explaining seal flutter behaviour in a comprehensive fashion. These parameters account for the effect of the pressure ratio, the cavity geometry, the fin clearance, the nodal diameter, the fluid swirl velocity, the vibration frequency and the torsion center location in a compact and interrelated form. A number of conclusions have been drawn by means of a thorough examination of the work-per-cycle expression, also known as the stability parameter by other authors. It was found that the physics of the problem strongly depends on the non-dimensional acoustic frequency. When the discharge time of the seal cavity is much greater than the acoustic propagation time, the damping of the system is very small and the amplitude of the response at the resonance conditions is very high. The model not only provides a unified framework for the stability criteria derived by Ehrich [1] and Abbot [2], but delivers an explicit expression for the work-per-cycle of a two-fin rotating seal. All the existing and well established engineering trends are contained in the model, despite its simplicity. Finally, the effect of swirl in the fluid is included. It is found that the swirl of the fluid in the inter-fin cavity gives rise to a correction of the resonance frequency and shifts the stability region. The non-dimensionalization of the governing equations is an essential part of the method and it groups physical effects in a very compact form. Part I of the paper details the derivation of the theoretical model and draws some preliminary conclusions. Part II of the corresponding paper analyzes in depth the implications of the model and outlines the extension to multiple cavity seals.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"92 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122749636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Study of Dynamic Phenomena Caused by Impulse Mistuning in Case of Self-Excitation","authors":"Peter Müller, A. Hartung, H. Hackenberg","doi":"10.1115/GT2018-75188","DOIUrl":"https://doi.org/10.1115/GT2018-75188","url":null,"abstract":"Further reduction of vibratory stresses of blades and vanes using an appropriate damping system is required whenever the total damping of the stage is insufficient to avoid High Cycle Fatigue during the life of the blades. An alternative to standard friction based damping systems are impulse mistuning systems — a kind of vibration impact induced non-linear energy sink. Previous publications introduced impulse mistuning systems for avoidance of HCF caused by forced synchronous vibrations of blades and vanes. This included the development of the system, analytical predictions of the effectiveness as well as experimental validation. The effectiveness of the impulse mistuning systems in the case of self-excitation (e.g. flutter) has not been investigated yet to the knowledge of the authors. In this paper, a numerical study of the dynamic phenomena taking place in lumped-parameter models with negative damping and different impulse mistuning systems is presented. One of the results shown is that energy transfer takes place, whereby the vibration initiates at one mode and after some time gets transferred into higher vibration at another mode.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134296476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigations on Transient Amplitude Amplification by Applying Intentional Mistuning","authors":"Klaus-Dieter Schlesier, L. P. Scheidt, J. Wallaschek","doi":"10.1115/GT2018-75514","DOIUrl":"https://doi.org/10.1115/GT2018-75514","url":null,"abstract":"Due to the changing demands in the energy production sector which leads to higher numbers of run ups and run downs, the importance of transient processes increase. Further information on the occurring blade vibration amplitudes during these processes could be used to explore new potential for longer lifetime and efficiency. Recent publications have shown that the amplitude of a mistuned blisk during a resonance passage can exceed the stationary response of the same system [1]. This underlines the importance of a better understanding of what happens during resonance passage. The effect is described as transient amplitude amplification of mistuned structures (TAMS). In this paper the effect will be investigated theoretically as well as in experiments. The main cause of the described effect seems to be the splitting of double eigenfrequencies due to mistuning. Therefore, the focus lies on methods to deliberately influence and seperate eigenfrequencies. First, simulations are done to predict parameter values which tend to show the TAMS effect. It is then shown how a significant transient amplitude amplification can be created on a test rig depending on the intentional mistuning. For realization an experimental setup with contactless measurement and acoustic excitation is deployed on a simplified blisk.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129471732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Damping Behavior of Acoustic Dominant Modes in an Aeroacoustic Test Rig Representing a Simplified Geometry of a High Pressure Radial Compressor","authors":"B. Barabas, D. Brillert, H. Dohmen, F. Benra","doi":"10.1115/GT2018-76629","DOIUrl":"https://doi.org/10.1115/GT2018-76629","url":null,"abstract":"Pressure ratios of modern high pressure radial compressors tend to increase along with pressure fluctuations and the excitation potential on the impellers. The vibrational interactions between side cavities, filled with high pressure fluid, and the impeller structure play an important role in designing a machine for reliable operation. However, they are not yet fully understood. Vibrations at frequencies that have been uncritical at lower pressure levels could become critical at a higher pressure level. Additionally, coupling effects between fluid and structure are becoming stronger at higher fluid densities. For a safe and reliable design, the excitation and the damping mechanism of coupled modes has to be better understood.\u0000 To understand the interaction, especially regarding the damping behavior, of coupled structure and acoustic modes, a comprehension of the behavior of the uncoupled or weakly coupled modes is required. The structural damping ratio is very small and it has been analyzed in existing literature extensively. The damping behavior of uncoupled acoustic modes, however, is not yet well investigated.\u0000 This paper focuses on the damping behavior of acoustic modes that are weakly coupled to structure modes. Measurement results gathered at the aeroacoustic test rig at the University of Duisburg-Essen are presented. The results show the influence of fluid pressure variations on the damping behavior of acoustic modes. Therefore, the response functions of some selected acoustic modes are evaluated with the Peak-to-Peak method. In general, the damping decreases with increasing fluid pressure. Furthermore, a relationship of the damping ratio, the kinematic viscosity, and the natural frequency of the acoustic modes has been detected.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"74 3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134011963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determination of Aerodynamic Damping at High Reduced Frequencies","authors":"Minghao Pan, P. Petrie-Repar, H. Mårtensson, T. Sun, Tobias Gezork","doi":"10.1115/GT2018-75294","DOIUrl":"https://doi.org/10.1115/GT2018-75294","url":null,"abstract":"In turbomachines, forced response of blades is blade vibrations due to external aerodynamic excitations and it can lead to blade failures which can have fatal or severe economic consequences. The estimation of the level of vibration due to forced response is dependent on the determination of aerodynamic damping. The most critical cases for forced response occur at high reduced frequencies. This paper investigates the determination of aerodynamic damping at high reduced frequencies. The aerodynamic damping was calculated by a linearized Navier-Stokes flow solver with exact 3D non-reflecting boundary conditions.\u0000 The method was validated using Standard Configuration 8, a two-dimensional flat plate. Good agreement with the reference data at reduced frequency 2.0 was achieved and grid converged solutions with reduced frequency up to 16.0 were obtained. It was concluded that at least 20 cells per wavelength is required. A 3D profile was also investigated: an aeroelastic turbine rig (AETR) which is a subsonic turbine case. In the AETR case, the first bending mode with reduced frequency 2.0 was studied. The 3D acoustic modes were calculated at the far-fields and the propagating amplitude was plotted as a function of circumferential mode index and radial order. This plot identified six acoustic resonance points which included two points corresponding to the first radial modes. The aerodynamic damping as a function of nodal diameter was also calculated and plotted. There were six distinct peaks which occurred in the damping curve and these peaks correspond to the six resonance points. This demonstrates for the first time that acoustic resonances due to higher order radial acoustic modes can affect the aerodynamic damping at high reduced frequencies.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"235 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132950333","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Flutter Analysis of a Flexible UHBR Fan at Different Flight Conditions","authors":"M. Schuff, J. Reisberg","doi":"10.1115/GT2018-76930","DOIUrl":"https://doi.org/10.1115/GT2018-76930","url":null,"abstract":"A flexible UHBR fan is investigated at different flight conditions with a focus on static deflections and aeroelastic stability. Operating points at varying inlet conditions, which are comparable according to the Mach similarity principle, are investigated. However, not all the aerodynamic characteristics remain identical and aerodynamic damping of mode shape vibrations is changed.\u0000 When steady deformations of the fan blades are taken into account, the deviation between different inlet conditions increases further. This is mainly due to torsional deflections, changing the effective angle of attack and causing a general shift of the compressor map.\u0000 Even though the subsequent changes in flutter predictions are not severe for most parts of the compressor map, the behavior at the boundaries is sensitive to the real flight condition.\u0000 As shown, the Mach similarity principle is not suitable for investigating aeroelastic stability throughout the whole flight envelope, especially when the static blade deformation is not neglectable. The reason for this can be found in the complex interaction between dimension-less numbers (Mach, Reynolds), sized values (pressure difference or aerodynamic loading, natural frequency) and their dependency on each other.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132577321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Representation and Analysis of Geometric Uncertainties in Rotor Blades","authors":"L. Carassale, S. Bruzzone, A. Cavicchi, M. Brunenghi","doi":"10.1115/GT2018-76385","DOIUrl":"https://doi.org/10.1115/GT2018-76385","url":null,"abstract":"Geometric uncertainties involved in the rotor blade manufacturing process are a major concern for designers. The deviation of the produced components from their nominal geometry have an impact on the Natural Frequencies (NF) that, under certain circumstances, may have negative effects on the dynamic forced response in operative conditions.\u0000 Geometric defects are usually limited by imposing dimensional tolerances based on empirical considerations, simplified approach that may lead to costly manufacturing requirements that still may not guarantee safe results.\u0000 This paper proposes a probabilistic representation of the geometric uncertainties for rotor blades and defines a procedure to evaluate their effects on the blade NFs. The deviation from nominal geometry is represented through the Principal Component Analysis (PCA) where it is expressed as a sum of characteristic geometric shapes (GUMs) modulated by mutually uncorrelated random variables (Principal Components, PC). The effect of each GUM is then linearly propagated on the blade NFs and a sensitivity matrix is finally defined.\u0000 The procedure is applied to a case-study that concerns a set of 50 nominally identical compressor blades and the ability of GUMs to represent the effects of geometric uncertainties is tested.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130375966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Non-Linear Vibration of Rotating Co-Rotational Two-Dimensional Beams With Large Displacement","authors":"Zihan Shen, B. Chouvion, F. Thouverez, A. Beley, Jean-Daniel Beley","doi":"10.1115/gt2018-75633","DOIUrl":"https://doi.org/10.1115/gt2018-75633","url":null,"abstract":"In order to achieve better performances and reduce fuel consumption, the new generation of turbomachines uses larger and lighter design, for instance the “open-rotor” concept, and is conceived to rotate at higher speeds. Parts of the structure become then even more likely to undergo large amplitude vibrations. Consequently, the conception of future aero-engine requires a sound and robust technique to predict the rotating machine vibrations considering geometrical nonlinearities (large displacements and large deformation). In this paper, the nonlinear vibrations of rotating beams with large displacements is investigated by the use of the Co-Rotational (C-R) finite element method. In the C-R approach, the full motion of each element is decomposed into a rigid body part and a pure deformational part by introducing a local coordinate system attached to the element. The utilization of the C-R method offers the possibility to treat geometrical nonlinearity directly with pre-extracted rigid body motion displacements. The originality we propose in this study is to derive its formulation in a rotating reference frame and include both centrifugal and gyroscopic effects. The nonlinear governing equations are obtained from Lagrange’s equations using a consistent expression for the kinetic energy. With this formulation, the spin-stiffening effect from geometrical nonlinearities due to large displacements is accurately handled. The proposed approach is then applied to several types of mechanical analysis (static large deformation, modal analysis at different spin speeds, and transient analysis after an impulsive force) to verify its accuracy and demonstrate its efficiency.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"148 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121521316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}