TY - GEN A1 - Maywald, Thomas A1 - Heinrich, Christoph Rocky A1 - Kühhorn, Arnold A1 - Schrape, Sven A1 - Backhaus, Thomas T1 - Prediction of Geometrically Induced Localization Effects Using a Subset of Nominal System Modes T2 - ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition June 17–21, 2019 Phoenix, Arizona, USA N2 - It is widely known that the vibration characteristics of blade integrated discs can dramatically change in the presence of manufacturing tolerances and wear. In this context, an increasing number of publications discuss the influence of the geometrical variability of blades on phenomena like frequency splitting and mode localization. This contribution is investigating the validity of a stiffness modified reduced order model for predicting the modal parameters of a geometrically mistuned compressor stage. In detail, the natural frequencies and mode shapes, as well as the corresponding mistuning patterns, are experimentally determined for an exemplary rotor. Furthermore, a blue light fringe projector is used to identify the geometrical differences between the actual rotor and the nominal blisk design. With the help of these digitization results, a realistic finite element model of the whole compressor stage is generated. Beyond that, a reduced order model is implemented based on the nominal design intention. Finally, the numerical predictions of the geometrically updated finite element model and the stiffness modified reduced order model are compared to the vibration measurement results. The investigation is completed by pointing out the benefits and limitations of the SNM-approach in the context of geometrically induced mistuning effects. KW - Blades KW - Compressors KW - Design KW - Disks KW - Finite element model KW - Manufacturing KW - Vibration measurement Y1 - 2019 UR - https://asmedigitalcollection.asme.org/GT/proceedings-abstract/GT2019/58691/V07BT35A012/1067131 SN - 978-0-7918-5869-1 U6 - https://doi.org/10.1115/GT2019-90884 ER - TY - GEN A1 - Maywald, Thomas A1 - Backhaus, Thomas A1 - Schrape, Sven A1 - Kühhorn, Arnold T1 - Geometric Model Update of Blisks and its Experimental Validation for a Wide Frequency Range T2 - ASME Turbo Expo 2017, GT2017-63446, June 26-30, 2017, Charlotte, NC, USA, Volume 7A N2 - The contribution discusses a model update procedure and its experimental validation in the context of blisk mistuning. Object of investigation is an industrial test blisk of an axial compressor which is milled from solid using a state of the art 5-axis milling machine. First, the blisk geometry is digitized by a blue light fringe projector. Digitization is largely automated using an industrial robot cell in order to guarantee high repeatability of the measurement results. Additionally, frequency mistuning patterns are identified based on vibration measurements. Here, the system excitation is realized by a modal impact hammer. The blade response is detected using a laser scanning vibrometer. Furthermore, all blades except the currently excited one are detuned with additional masses. Applying these masses allows to identify a blade dominated natural frequency for each blade and every mode of interest. Finally, these blade dominated frequencies are summarized to mode specific mistuning patterns. The key part of the contribution presents a model update approach which is focused on small geometric deviations between real engine parts and idealized simulation models. Within this update procedure the nodal coordinates of an initially tuned finite element blisk model were modified in order to match the geometry of the real part measured by blue light fringe projection. All essential pre- and post-processing steps of the mesh morphing procedure are described and illustrated. It could be proven that locally remaining geometric deviations between updated finite element model and the optical measurement results are below 5 μm. For the purpose of validation blade dominated natural frequencies of the updated finite element blisk model are calculated for each sector up to a frequency of 17 kHz. Finally, the numerically predicted mistuning patterns are compared against the experimentally identified counterparts. At this point a very good agreement between experimentally identified and numerically predicted mistuning patterns can be proven across several mode families. Even mistuning patterns of higher modes at about 17 kHz are well predicted by the geometrically mistuned finite element model. Within the last section of the paper, possible uncertainties of the presented model update procedure are analyzed. As a part of the study the digitization of the investigated blisk has been repeated for ten times. These measurement results serve as input for the model update procedure described before. In the context of this investigation ten independent geometrical mistuned simulation models are created and the corresponding mistuning patterns are calculated. Copyright © 2017 by Rolls-Royce Deutschland Ltd & Co KG KW - Lasers KW - Optical Measurement Y1 - 2017 SN - 978-0-7918-5092-3 U6 - https://doi.org/10.1115/GT2017-63446 PB - ASME CY - New York, NY ER - TY - GEN A1 - Backhaus, Thomas A1 - Maywald, Thomas A1 - Schrape, Sven A1 - Voigt, Matthias A1 - Mailach, Roland T1 - A Parametrization Describing Blisk Airfoil Variations Referring to Modal Analysis T2 - ASME Turbo Expo 2017, GT2017-64243, June 26-30, 2017, Charlotte, NC, USA, Volume 7A N2 - This paper will present a way to capture the geometric blade by blade variations of a milled from solid blisk as well as the manufacturing scatter. Within this idea it is an essential task to digitize the relevant airfoil surface as good as possible to create a valid surface mesh as the base of the upcoming evaluation tasks. Since those huge surface meshes are not easy to handle and are even worse in getting quantified and easy interpretable results, it should be aimed for an easily accessible way of presenting the geometric variation. The presented idea uses a section based airfoil parametrization that is based on an extended NACA-airfoil structure to ensure the capturing of all occurring characteristic geometry variations. This Paper will show how this adapted parametrization method is suitable to outline all the geometric blade by blade variation and even more, refer those airfoil design parameters to modal analysis results such as the natural frequencies of the main mode shapes. This way, the dependencies between the modal and airfoil parameters will be proven. KW - Airfoils KW - Modal Analysis Y1 - 2017 SN - 978-0-7918-5092-3 U6 - https://doi.org/10.1115/GT2017-64243 PB - ASME CY - New York, NY ER - TY - GEN A1 - Beirow, Bernd A1 - Maywald, Thomas A1 - Figaschewsky, Felix A1 - Kühhorn, Arnold A1 - Heinrich, Christoph Rocky A1 - Giersch, Thomas T1 - Simplified Determination of Aerodynamic Damping for Bladed Rotors, Part 1: Experimental Validation at Rest T2 - ASME Turbo Expo 2016, Turbomachinery Technical Conference and Exposition, Volume 7B, Structures and Dynamics, Seoul, South Korea, June 13–17, 2016 N2 - Considering both a radial turbine rotor of a turbocharger and an axial compressor test blisk at rest, aerodynamic damping characteristics are experimentally and numerically analyzed. Linear dependencies of modal damping ratios on the ambient pressure or the acoustic impedance, respectively, could be shown within experiments carried out inside a pressure chamber. The impact of the ambient air clearly dominates the modal damping ratios compared to the minor contribution of the structure. Assuming that acoustic emission can be regarded as main source of aerodynamic damping a simplified approach for its determination is introduced which only depends on natural frequency, mode shape and acoustic impedance. It is shown that a satisfying match between experiment and computation is achieved for those cases which are dedicated to sufficiently small ratios between wave lengths of acoustic emissions and blade distances. Y1 - 2016 SN - 978-0-7918-4984-2 U6 - https://doi.org/10.1115/GT2016-56535 N1 - Paper No. GT2016-56535 PB - ASME CY - New York, NY ER - TY - CHAP A1 - Maywald, Thomas A1 - Kühhorn, Arnold A1 - Schrape, Sven T1 - Experimental Validation of a Model Update Procedure Focusing on Small Geometric Deviations T2 - ECCOMAS VII European Congress on Computational Methods in Applied Sciences and Engineering, Crete, Greece, June 5-10, 2016 N2 - This contribution presents a model update procedure and its experimental validation using the example of a blade integrated disk rotor. This so called blisk is discretized using the finite element method. It is well known that numerical blisk models based on the ideal tuned design show major differences in structural dynamic behavior compared to the real rotor. In this context a modification of the mechanical simulation model should lead to a better accordance of numerical results and the real blisk characteristics. The described model update procedure utilizes data of an optical 3D measurement system. Using this data enables to identify geometric deviations between the ideal design and its real counterpart. Within the update procedure the originally tuned finite element mesh is modified in order to match the measured geometry of the real part. This is done by defining several morph regions. The outer surface nodes of these morph regions change their position along the surface normal vector until they meet the defined deviation constraint. Based on eigenvalue calculations employing free boundary conditions the sensitivity of structural dynamic behavior is shown with respect to small geometric changes. Finally computed eigenvalues and eigenvectors of the updated simulation model are compared with vibration measurement data. A laser Doppler vibrometer is used to detect the vibration responses of the impact excited structure. All experiments are carried out under technical vacuum conditions in order to minimize ambient air damping. In the context of an experimental modal analysis this low damping condition helps to identify more natural frequencies of the investigated structure. This leads to a much more efficient model validation. Y1 - 2016 UR - https://www.eccomas2016.org/proceedings/pdf/7386.pdf ER - TY - THES A1 - Maywald, Thomas T1 - Modellierung und Simulation integral gefertigter Verdichterlaufräder auf der Grundlage einer dreidimensionalen Oberflächenvermessung N2 - Integral gefertigte Verdichterlaufräder repräsentieren eine fortschrittliche Baugruppe moderner Turbomaschinen. Eine dauerfeste Auslegung derartiger Komponenten kann sich mitunter als schwierig erweisen. Ursache hierfür ist, dass bereits kleinste Variationen der Bauteilkontur beziehungsweise der Materialeigenschaften eine drastische Veränderung des mechanischen Verhaltens bewirken können. Aus diesem Grund besteht ein übergeordnetes Interesse diese sogenannte Laufradverstimmung bereits im Auslegungsprozess einer Maschine zu berücksichtigen. Die vorliegende Arbeit unterstützt dieses Anliegen, indem Möglichkeiten dargestellt werden, die fertigungsbedingten Variationen der Bauteilkontur messtechnisch zu erfassen und diese im Modellierungsprozess mit einzubeziehen. Ziel ist es darüber hinaus nachzuweisen, dass eine Modellanpassung auf Grundlage der realen Bauteilgeometrie die Aussagekraft der Simulation deutlich erhöhen kann. Sämtliche zum Einsatz kommenden Verfahren zur Modellierung und Modellanpassung sowie die benötigten experimentellen Aufbauten werden ausführlich beschrieben. Auf Grundlage der generierten Messdaten, Modelle und Simulationsergebnisse gelingt es schließlich Gestaltungshinweise für eine effiziente Modellierung des betrachteten Laufradbeispiels zu formulieren. Im Anschluss stellt der Abgleich berechneter und experimentell identifizierter Eigenfrequenzen und Eigenformen die Validität der verwendeten Modelle unter Beweis. Weiterhin wird gezeigt, inwiefern sich der unvermeidbare zufällige Messfehler im Rahmen der optischen Geometrievermessung auf die numerischen Berechnungsergebnisse auswirken kann. Den Abschluss bildet eine Gegenüberstellung zweier verschiedener Modellanpassungsmethoden. Der Vergleich stützt sich auf die Ergebnisse eines geometrisch modifizierten beziehungsweise eines steifigkeitsproportional angepassten Modells. Die Arbeit kommt zu dem Schluss, dass eine Modellanpassung auf der Grundlage einer dreidimensionalen Oberflächenvermessung die Aussagekraft einer Simulation erheblich verbessern kann. Dabei ermöglichte es die vorgestellte Vorgehensweise, das verstimmungsbedingt modifizierte mechanische Eigenschaftsprofil eines realen Verdichterlaufrades richtig wiederzugeben. N2 - Blade integrated disks (blisk) represent a state of the art technology in modern turbo machinery design. Nevertheless, there are several difficulties with respect to a robust design of such parts. Especially the manufacturing process causes small geometric deviations as well as a scattering of material properties. Those uncertainties are called mistuning. They lead to a major modification of the dynamical behaviour of a blisk and have to be considered within engine design process. The present work deals with the effects of geometric blisk-mistuning. Therefore, manufacturing driven variations of blisk geometry are experimentally quantified using a blue light fringe projector. Further on, the corresponding finite element model of the investigated compressor blisk is modified in order to match the digitization results. All essential pre- and post-processing steps of the model update procedure are described and illustrated. The modified model is used to calculate blade alone frequencies as well as natural frequencies and mode shapes of the whole blisk. Subsequently, the numerical results are compared with the outcome of a comprehensive vibration measurement campaign. At this point a very good match between experimentally identified and numerically predicted modal parameters can be proven across several mode families. Next, within a repeatability study the object of research is digitized ten times. The aim of the investigation is to show the sensitivity of numerical results with respect to the unavoidable measurement errors. Finally, the presented geometric model update procedure is compared against a stiffness proportional model update approach that is commonly used to predict mistuning effects. In conclusion, it can be said that a geometrically updated finite element model is able to sufficiently predict the mistuned modal parameters of a blisk. Basing on optical measurement results the simulation validity can be significantly improved in this context. KW - Verdichterlaufrad KW - Modellierung Y1 - 2018 SN - 978-3-95908-135-1 PB - TUDpress CY - Dresden ER - TY - CHAP A1 - Beirow, Bernd A1 - Maywald, Thomas A1 - Kühhorn, Arnold T1 - Mistuning and Damping Analysis of a Radial Turbine Blisk in Varying Ambient Conditions T2 - ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Volume 7B: Structures and Dynamics Düsseldorf, Germany, June 16–20, 2014, Paper GT2014-25521 N2 - A mistuned radial turbine impeller is analyzed with respect to the impact of varying ambient pressures and temperatures as well on frequency response functions and modal damping ratios. Beginning at room conditions, a finite element model of an impeller wheel at rest is updated based on experimentally determined mistuning in terms of blade dominated frequencies. The following numerical forced response analyses yield a maximum blade displacement amplification of 67% compared to the tuned reference. In addition, modal damping ratios are determined in dependence on the ambient pressure ranging from technical vacuum at 1 mbar up to 6000 mbar in a pressure chamber. Shaker excitation and laser Doppler vibrometry response measurement is employed in this context. A linear dependence of modal damping ratios on ambient pressure and a dominating damping contribution of the surrounding air even for higher modes could be proved. Moreover, the experimental determination of frequency response functions (FRF) at technical vacuum yields a better separation of resonance peaks compared to room conditions at 1013 mbar and hence, this data allows for more accurate model-updates in principle. It is proved that numerical models updated regarding mistuning at room conditions are well suited to predict the forced response at arbitrary pressures if measured modal damping ratios at these pressures are considered. Finally, within analyzing the effect of increasing structural temperatures with the surrounding air at 1013 mbar included slightly decreasing resonance frequencies but strongly increasing FRF-amplitudes are determined. Copyright © 2014 by ASME KW - Damping KW - Turbines Y1 - 2014 SN - 978-0-7918-4577-6 U6 - https://doi.org/10.1115/GT2014-25521 PB - ASME ER - TY - CHAP A1 - Maywald, Thomas A1 - Beirow, Bernd A1 - Heinrich, Christoph Rocky A1 - Kühhorn, Arnold T1 - Vacuum Spin Test Series of a Turbine Impeller with Focus on Mistuning and Damping by Comparing Tip Timing and Strain Gauge Results T2 - ASME Turbo Expo 2015: Turbine Technical Conference and Exposition Volume 7B: Structures and Dynamics Montreal, Quebec, Canada, June 15–19, 2015 N2 - This paper describes preparation, execution and evaluation of a comprehensive bladed disk spin test series. At the example of an turbine impeller the effects of rotation and temperature are analyzed with special focus on mistuning and damping. The forced response is measured synchronously via 13 identical positioned strain gauges on each blade as well as via blade tip-timing. Subsequently it is possible to compare the results of both systems. During the test series rotational speed varies in the range from 10.000 up to 19.000 RPM. Simultaneously, the wheel is heated up to 820 K by an oven. A number of pre-selected natural frequencies, damping ratios and operating deflection shapes are evaluated and compared with respect to different rotational speeds and impeller temperatures. Copyright © 2015 by ASME KW - Rotation KW - Vacuum KW - Impellers KW - Damping KW - Turbines KW - Strain gages Y1 - 2015 SN - 978-0-7918-5677-2 U6 - https://doi.org/10.1115/GT2015-42649 PB - ASME CY - New York, NY ER - TY - CHAP A1 - Maywald, Thomas T1 - Grundlegende Charakterisierung des Eigenschwingverhaltens eines zyklisch symmetrischen Mehrmassenschwingers mittels analytischer Methoden T2 - Deutscher Luft- und Raumfahrtkongress, Tagungsband Bremen 2011, Manuskripte KW - Eigenschwingverhalten KW - Mistuning KW - zyklisch symmetrischer Mehrmassenschwinger Y1 - 2011 SP - 809 EP - 816 PB - DGLR CY - Bonn ER - TY - GEN A1 - Maywald, Thomas A1 - Beirow, Bernd A1 - Kühhorn, Arnold T1 - Mistuning und Dämpfung von Radialturbinenrädern T2 - MTZ - Motortechnische Zeitschrift N2 - Moderne Verbrennungskraftmaschinen müssen ein stetig wachsendes Anforderungsprofil in Bezug auf Wirtschaftlichkeit, Leistung und Umweltfreundlichkeit erfüllen. In diesem Zusammenhang hat die Turboaufladung von Verbrennungsmotoren an Bedeutung gewonnen. Bei Turboladern kleiner und mittlerer Baugröße, deren Turbinen einen Durchmesser zwischen 30 und 250 mm aufweisen, kommen vornehmlich gegossene Laufräder zum Einsatz. Am Institut für Verkehrstechnik der Brandenburgischen Technischen Universität Cottbus-Senftenberg wurde im Rahmen eines FVV-Forschungsvorhabens der Einfluss charakteristischer Betriebsgrößen eines Turboladers auf das strukturdynamische Verhalten solcher Radialturbinenräder untersucht. Y1 - 2015 U6 - https://doi.org/10.1007/s35146-015-0043-7 SN - 2192-8843 VL - 76 IS - 06 SP - 68 EP - 75 ER -