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 -