@inproceedings{BeirowFigaschewskyKuehhorn, author = {Beirow, Bernd and Figaschewsky, Felix and K{\"u}hhorn, Arnold}, title = {An Inverse Approach to Identify Tuned Aerodynamic Damping, System Frequencies, and Mistuning, Part 2: Application to Blisks at Rest}, series = {Proceedings of the 15th International Symposium on Unsteady Aerodynamics, Aeroacoustics \& Aeroelasticity of Turbomachines, ISUAAAT15, 24-27 September 2018, University of Oxford, UK}, booktitle = {Proceedings of the 15th International Symposium on Unsteady Aerodynamics, Aeroacoustics \& Aeroelasticity of Turbomachines, ISUAAAT15, 24-27 September 2018, University of Oxford, UK}, publisher = {ISUAAAT Scientific Committee}, pages = {2}, language = {en} } @inproceedings{FigaschewskyKuehhorn, author = {Figaschewsky, Felix and K{\"u}hhorn, Arnold}, title = {An Inverse Approach to Identify Tuned Aerodynamic Damping, System Frequencies, and Mistuning, Part 1: Theory Under Rotating Conditions}, series = {Proceedings of the 15th International Symposium on Unsteady Aerodynamics, Aeroacoustics \& Aeroelasticity of Turbomachines, ISUAAAT15, 24-27 September 2018, University of Oxford, UK}, booktitle = {Proceedings of the 15th International Symposium on Unsteady Aerodynamics, Aeroacoustics \& Aeroelasticity of Turbomachines, ISUAAAT15, 24-27 September 2018, University of Oxford, UK}, publisher = {ISUAAAT Scientific Committee}, pages = {12}, language = {en} } @inproceedings{KochBeirowFilippatosetal., author = {Koch, Ilja and Beirow, Bernd and Filippatos, Angelos and K{\"u}hhorn, Arnold and Gude, Maik}, title = {Methodical Approach for Simulation the Vibration of Damaged Fibre Reinforced Composite Rotors Under Consideration of Aerodynamic Influences}, series = {18th European Conference on Composite Materials (ECCM18), Athen (Griechenland), 25.-28. Juni 2018}, booktitle = {18th European Conference on Composite Materials (ECCM18), Athen (Griechenland), 25.-28. Juni 2018}, pages = {8}, language = {en} } @inproceedings{BeirowKuehhornFigaschewskyetal., author = {Beirow, Bernd and K{\"u}hhorn, Arnold and Figaschewsky, Felix and Bornholm, Alfons and Repetckii, Oleg V.}, title = {Forced Response Reduction of a Blisk by Means of Intentional Mistuning}, series = {ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition, Volume 7C: Structures and Dynamics, Oslo, Norway, June 11-15, 2018}, booktitle = {ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition, Volume 7C: Structures and Dynamics, Oslo, Norway, June 11-15, 2018}, publisher = {ASME}, address = {New York, NY}, isbn = {978-0-7918-5115-9}, doi = {10.1115/GT2018-76584}, pages = {10}, abstract = {The effect of intentional mistuning has been analyzed for an axial turbocharger blisk with the objective of limiting the forced response due to low engine order excitation (LEO). The idea behind the approach was to increase the aerodynamic damping for the most critical fundamental mode in a way that a safe operation is ensured without severely losing aerodynamic performance. Apart from alternate mistuning a more effective mistuning pattern is investigated, which has been derived by means of optimization employing genetic algorithms. In order to keep the manufacturing effort as small as possible only two blade different geometries have been allowed which means that an integer optimization problem has been formulated. Two blisk prototypes have been manufactured for the purpose of demonstrating the benefit of the intentional mistuning pattern identified in this way: A first one with and a second one without employing intentional mistuning. The real mistuning of the prototypes has been experimentally identified. It is shown that the benefit regarding the forced response reduction is retained in spite of the negative impact of unavoidable additional mistuning due to the manufacturing process. Independently, further analyzes have been focused on the robustness of the solution by considering increasing random structural mistuning and aerodynamic mistuning as well. The latter one has been modeled by means of varying aerodynamic influence coefficients (AIC) as part of Monte Carlo simulations. Reduced order models have been employed for these purposes.}, language = {en} } @inproceedings{KoberKuehhornKeskin, author = {Kober, Markus and K{\"u}hhorn, Arnold and Keskin, Akin}, title = {Instability problems in implicit transient FEM simulations of fast rotating elastic structures - Description of the phenomenon and possible solutions}, series = {Proceedings of NAFEMS DACH Conference 2018, Bamberg, May 14-16, 2018}, booktitle = {Proceedings of NAFEMS DACH Conference 2018, Bamberg, May 14-16, 2018}, publisher = {NAFEMS Deutschland, {\"O}sterreich, Schweiz GmbH}, address = {Grafing}, isbn = {978-1-910643-14-3}, pages = {48 -- 52}, language = {en} } @inproceedings{WeberKuehhorn, author = {Weber, Robby and K{\"u}hhorn, Arnold}, title = {Mistuning und D{\"a}mpfung radialer Turbinen- und Verdichterlaufr{\"a}der}, series = {Abschluss- und Zwischenberichte der Forschungsstellen Turbomaschinen, Fr{\"u}hjahrstagung 2018, Tagungsband 2018, Bad Neuenahr}, booktitle = {Abschluss- und Zwischenberichte der Forschungsstellen Turbomaschinen, Fr{\"u}hjahrstagung 2018, Tagungsband 2018, Bad Neuenahr}, publisher = {Forschungsvereinigung Verbrennungskraftmaschinen e.V.}, address = {Frankfurt am Main}, pages = {159 -- 190}, language = {de} } @inproceedings{KoberKuehhornKeskin, author = {Kober, Markus and K{\"u}hhorn, Arnold and Keskin, Akin}, title = {Optimization of Newmark-Euler Time-Integration Parameters for a Stable and Efficient Implicit Simulation of Rotating Elastic Structures}, series = {Proceedings of 15th German LS-DYNA Forum}, booktitle = {Proceedings of 15th German LS-DYNA Forum}, publisher = {DYNAmore GmbH}, address = {Stuttgart}, isbn = {978-3-9816215-5-6}, pages = {235 -- 238}, language = {en} } @inproceedings{FigaschewskyKuehhornGiersch, author = {Figaschewsky, Felix and K{\"u}hhorn, Arnold and Giersch, Thomas}, title = {A Finite Element Based Least Square Fit for the Assessment of Integral and Non-Integral Vibrations With Blade Tip Timing}, series = {Proceedings of ISROMAC 2017, Maui, Hawaii, December 16-21, 2017}, booktitle = {Proceedings of ISROMAC 2017, Maui, Hawaii, December 16-21, 2017}, pages = {9}, abstract = {This paper aims at improving the robustness and accuracy of the least square fit technique utilized in blade tip timing (BTT) measurements of blade vibrations by proposing two modifications. The first proposal is to replace the lines of the original least square problem by differences of consecutive lines. Thereby, the static deflection as well as the circumferential blade positioning error cancels out and the robustness is improved by removing these uncertainties inherently. The second proposal is to replace the fit of piecewise constant vibration amplitudes within the chosen block length by a linear or cubic spline in the frequency (integral) or time (non-integral) regime. This does not only suppress overshoots due to distorted acceleration or deceleration manoeuvres but also allows for a "coarser analysis grid" (i.e. larger block length) without loosing amplitude accuracy. Thereby it smooths out random errors more efficiently and increases the orthogonality of the relevant EO or vibration frequency to unwanted signal components.}, language = {en} } @inproceedings{BeirowFigaschewskyKuehhornetal., author = {Beirow, Bernd and Figaschewsky, Felix and K{\"u}hhorn, Arnold and Bornholm, Alfons}, title = {Vibration Analysis of an Axial Turbine Blisk with Optimized Intentional Mistuning Pattern}, series = {Proceedings of ISROMAC 2017, Maui, Hawaii, December 16-21, 2017}, booktitle = {Proceedings of ISROMAC 2017, Maui, Hawaii, December 16-21, 2017}, pages = {9}, abstract = {Aiming to limit the forced response of an axial turbine blisk for ship Diesel engine applications efforts have been made to increase the aerodynamic damping contribution for the most critical modes. In this regard the potential of intentional mistuning is investigated since it offers the opportunity to ensure a safe operation without a severe loss of aerodynamic performance. Genetic algorithms have been chosen to derive an optimized mistuning pattern. In order to keep the manufacturing effort within a limit only two possible blade geometries are allowed which means that an integer optimization problem has been formulated. For the purpose of demonstrating the benefit of the intentional mistuning pattern found, two blisk prototypes have been manufactured: One with and another one without employing intentional mistuning for purposes of comparison. Furthermore, this offers the opportunity for an experimental determination of mistuning being really manufactured and other modal properties as well. The experimental data basis is employed to update structural models which are well suited to demonstrate the forced response reduction under operational conditions.}, language = {en} } @inproceedings{HanschkeKuehhornSchrapeetal., author = {Hanschke, Benjamin and K{\"u}hhorn, Arnold and Schrape, Sven and Giersch, Thomas}, title = {Consequences of Borescope Blending Repairs on Modern HPC Blisk Aeroelasticity}, series = {Proceedings of ISROMAC 2017, Maui, Hawaii, December 16-21, 2017}, booktitle = {Proceedings of ISROMAC 2017, Maui, Hawaii, December 16-21, 2017}, pages = {8}, abstract = {Objective of this paper is to analyse the consequences of borescope blending repairs on the aeroelastic behaviour of a modern HPC blisk. To investigate the blending consequences in terms of aerodynamic damping and forcing changes, an exemplary blending of a rotor blade is modelled. Steady state flow parameters like total pressure ratio, polytropic efficiency and the loss coefficient are compared. Furthermore, aerodynamic damping is computed utilising the AIC approach for both geometries. Results are confirmed by SPF simulations for specific nodal diameters of interest. Finally, an unidirectional forced response analysis for the nominal and the blended rotor is conducted to determine the aerodynamic force exciting the blade motion. Fourier transformation of the forcing signal yields to the frequency content as well as the forcing amplitudes. As a result of the present analysis, the amplification of expected blade vibration amplitude is computed.}, language = {en} }