@inproceedings{BeirowKuehhornFigaschewskyetal., author = {Beirow, Bernd and K{\"u}hhorn, Arnold and Figaschewsky, Felix and Nipkau, Jens}, title = {Effect of Mistuning and Damping on the Forced Response of a Compressor Blisk Rotor}, series = {ASME Turbo Expo 2015: Turbine Technical Conference and Exposition Volume 7A: Structures and Dynamics Montreal, Quebec, Canada, June 15-19, 2015}, booktitle = {ASME Turbo Expo 2015: Turbine Technical Conference and Exposition Volume 7A: Structures and Dynamics Montreal, Quebec, Canada, June 15-19, 2015}, publisher = {ASME}, address = {New York, NY}, isbn = {978-0-7918-5677-2}, doi = {10.1115/GT2015-42036}, abstract = {The forced response of an E3E-type high pressure compressor blisk front rotor is analyzed with regard to intentional mistuning and its robustness towards additional random mistuning. Both a chosen alternating mistuning pattern and artificial mistuning patterns optimized concerning the forced response are considered. Focusing on three different blade modes, subset of nominal system mode-based reduced order models are employed to compute the forced response. The disk remains unchanged while the Young's modulus of each blade is used to define the particular mistuning pattern. The well established aerodynamic influence coefficient technique is employed to model aeroelastic coupling and hence to consider the strongly mode- and inter blade phase angle-dependent aerodynamic damping contribution. It has been found that a reduction of the maximum forced response beyond that of the tuned reference can be achieved for particular mistuning patterns and all modes considered. This implies an exciting engine order which would cause a low nodal diameter mode in case of a tuned blisk. At best a nearly 50\% reduction of maximum response magnitudes is computed for the fundamental bending mode and large mistuning. The solution proved to be robust towards additional random mistuning of reasonable magnitude, which is of particular interest with regard to a potential technical realization. In case of small mistuning as assumed for the first torsion and the longitudinal bending mode the advantage of achieving response magnitudes beyond the tuned reference gets lost indeed, if random mistuning is superimposed. However, mostly a lower response level is calculated compared to responses obtained from models adjusted to mistuning determined by experiment. Copyright © 2015 by ASME}, language = {en} } @misc{FigaschewskyKuehhornBeirowetal., author = {Figaschewsky, Felix and K{\"u}hhorn, Arnold and Beirow, Bernd and Giersch, Thomas and Schrape, Sven and Nipkau, Jens}, title = {An inverse approach to identify tuned aerodynamic damping, system frequencies and mistuning - Part 3: Application to engine data}, series = {ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition, June 17-21, 2019, Phoenix, Arizona, USA}, journal = {ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition, June 17-21, 2019, Phoenix, Arizona, USA}, isbn = {978-0-7918-5868-4}, doi = {10.1115/GT2019-91337}, pages = {13}, abstract = {A novel approach for the identification of tuned aerodynamic damping, system frequencies, forcing and mistuning has been introduced in the first part of this paper. It is based on the forced response equations of motion for a blade dominated mode family. A least squares formulation allows to identify the system's parameters directly from measured frequency response functions (FRFs) of all blades recorded during a sweep through a resonance. The second part has dealt with its modification and application to experimental modal analyses of blisks at rest. This 3rd part aims at presenting the application of the approach to blade tip timing (BTT) data acquired in rig tests. Therefore, blisk rotors of two different engines are studied: a single stage fan rig and a 4.5 stage high pressure compressor (HPC) rig. The rig test campaign of the fan blisk included also an intentional mistuning experiment that allows to study the performance of the identification approach for a similar rotor with two different mistuning levels. It is demonstrated that the approach can identify aerodynamic damping curves, system frequencies, mistuning pattern and forced travelling wave modes (TWMs) from state of the art BTT data monitored during rig or engine tests. All derived mistuning patterns could be verified with reference measurements at standstill. The derived aerodynamic damping curves and system frequencies show a reasonable agreement with simulations. For the HPC case a multitude of excited TWMs could be identified which also lines up with previous simulations.}, language = {en} } @misc{HeinrichUnglaubeBeirowetal., author = {Heinrich, Christoph Rocky and Unglaube, Tina and Beirow, Bernd and Brillert, Dieter and Steff, Klaus and Petry, Nico}, title = {Surrogate Models for the Prediction of Damping Ratios in Coupled Acoustoelastic Rotor-Cavity Systems}, series = {Journal of Engineering for Gas Turbines and Power}, volume = {144}, journal = {Journal of Engineering for Gas Turbines and Power}, number = {8}, issn = {1528-8919}, doi = {10.1115/1.4054567}, abstract = {Centrifugal compressors are versatile machines that many industries employ for a wide range of different applications, including the production of highly compressed gases. During the last decades, comprehensive research was conducted on the impact of high-pressure operating conditions on the vibrational behavior of radial compressors. In various studies, acoustic modes building up in the side cavities were found to be a potential source of high cycle fatigue. Nowadays, it is well-known that an increase in gas pressure levels leads to a more pronounced fluid-structure interaction between the side cavities and the impeller resulting in a frequency shift of the acoustic and structural modes. In a recently published paper, the authors presented a generalized model which can predict this behavior. As it is not always possible to avoid operating close to or accelerating through a resonance, it is crucial to know the damping present within the system. Currently, only a few publications concentrate on the damping of radial impellers. Therefore, the authors present measurement data acquired from a test rig at the University of Duisburg-Essen, which reveals the damping behavior of a disk under varying operating conditions. Two surrogate models are proposed to predict the identified damping behavior. The first one is based solely on a one-dimensional piston model and the second approach uses an enhanced version of the generalized method. Finally, the measurement data is used to validate both surrogate systems.}, language = {en} } @misc{ZobelFuhrerVogtetal., author = {Zobel, Arthur and Fuhrer, Christopher and Vogt, Damian and Nakos, Alex and Beirow, Bernd and Blessing, Alexander and Zippack, Carolin}, title = {On the Influence of Bearing Modeling Details on the Dynamical System Effects of a Mid-Size Turbocharger Rotor}, series = {Proceedings of ASME Turbo Expo 2023, Boston, Massachusetts, June 26-30, 2023, Volume 11, A. Aerodynamics excitation and damping, bearing and seal dynamics}, journal = {Proceedings of ASME Turbo Expo 2023, Boston, Massachusetts, June 26-30, 2023, Volume 11, A. Aerodynamics excitation and damping, bearing and seal dynamics}, publisher = {ASME}, address = {New York}, isbn = {978-0-7918-8705-9}, doi = {10.1115/GT2023-102098}, pages = {11}, abstract = {The investigation of the excitation of turbocharger rotors to quantify the High-Cycle-Fatigue (HCF) risk is still a demanding task nowadays. The common way to investigate such phenomena is to look either at the turbine or the compressor rotor in an isolated manner. This approach gives mostly reliable results, if the investigated excitation pattern is stemming from the up- or downstream parts in the machine. However, there is a lack of studies on the existence of responses, which may exist due to the coupling between compressor and turbine. With the increase of computational capabilities and the improvement of FE tools, it is possible to create a full rotor model featuring the compressor and the turbine wheel as well as the bearings to investigate the dynamical behavior of the full rotor at different resonances. To carry out such an investigation, both wheels and the shaft are modeled. The axial, as well as the radial bearings, are modelled realistically by suitable elements and values. Due to the asymmetry of damping and stiffness properties, the resulting system matrices are asymmetrical as well. The eigenfrequencies and mode shapes of such a system can be obtained in a reasonable time by carrying out a modal analysis using the QR damp eigensolver in Ansys APDL. The present paper will show the differences in dynamical system effects of a mid-size turbocharger with different shaft support conditions. For this purpose, the FE simulation with the full rotor and fixed support at the radial bearing position, which is comparable to the isolated rotor consideration, will be compared to the model featuring the detailed bearing modeling with stiffness and damping values originating from the OEM. Besides the detailed process of modeling the bearings, the mutual influence of both rotor wheels at certain eigenfrequencies is analyzed. This allows to conclude on the level of detailing needed to ensure that dynamical system effects are properly accounted.}, language = {en} }