TY - CHAP A1 - Kober, Markus A1 - Kühhorn, Arnold A1 - Keskin, Akin A1 - Singh, Kai Navtej T1 - Challenges and opportunities of thermomechanical FEM simulations of high fidelity aero-engine models by implicit time-integration T2 - Proceedings of ISABE 2017, ISABE-2017-22568, Manchester, September 3.-8., 2017 Y1 - 2017 UR - https://isabe2017.org/ PB - ISABE ER - TY - CHAP A1 - Figaschewsky, Felix A1 - Kühhorn, Arnold A1 - Giersch, Thomas T1 - A Finite Element Based Least Square Fit for the Assessment of Integral and Non-Integral Vibrations With Blade Tip Timing T2 - Proceedings of ISROMAC 2017, Maui, Hawaii, December 16-21, 2017 N2 - 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. KW - Blade Tip Timing KW - Non-Intrusive Measurements KW - Blade Vibration Y1 - 2017 UR - http://isromac-isimet.univ-lille1.fr/index.php?rubrique=abstract17_&num=2 ER - TY - CHAP A1 - Hanschke, Benjamin A1 - Kühhorn, Arnold A1 - Schrape, Sven A1 - Giersch, Thomas T1 - Consequences of Borescope Blending Repairs on Modern HPC Blisk Aeroelasticity T2 - Proceedings of ISROMAC 2017, Maui, Hawaii, December 16-21, 2017 N2 - 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. KW - Aeroelasticity KW - Compressor Blisk KW - Blending Repair KW - Forced Response KW - Arodynamic Damping Y1 - 2017 UR - http://isromac-isimet.univ-lille1.fr/index.php?rubrique=abstract17_&num=2 ER - TY - CHAP A1 - Beirow, Bernd A1 - Figaschewsky, Felix A1 - Kühhorn, Arnold A1 - Bornholm, Alfons T1 - Vibration Analysis of an Axial Turbine Blisk with Optimized Intentional Mistuning Pattern T2 - Proceedings of ISROMAC 2017, Maui, Hawaii, December 16-21, 2017 N2 - 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. KW - Blisk KW - Intentional Mistuning KW - Low Engine Order Excitation Y1 - 2017 UR - http://isromac-isimet.univ-lille1.fr/index.php?rubrique=abstract17_&num=21 ER - TY - GEN A1 - Beirow, Bernd A1 - Figaschewsky, Felix A1 - Kühhorn, Arnold A1 - Bornholm, Alfons T1 - Modal Analyses of an Axial Turbine Blisk With Intentional Mistuning T2 - Journal of Engineering for Gas Turbines and Power N2 - The potential of intentional mistuning to reduce the maximum forced response is analyzed within the development of an axial turbine blisk for ship diesel engine turbocharger applications. The basic idea of the approach is to provide an increased aerodynamic damping level for particular engine order excitations and mode shapes without any significant distortions of the aerodynamic performance. The mistuning pattern intended to yield a mitigation of the forced response is derived from an optimization study applying genetic algorithms. Two blisk prototypes have been manufactured a first one with and another one without employing intentional mistuning. Hence, the differences regarding the real mistuning and other modal properties can be experimentally determined and evaluated as well. In addition, the experimental data basis allows for updating structural models which are well suited to compute the forced response under operational conditions. In this way, the real benefit achieved with the application of intentional mistuning is demonstrated. KW - Modal Analyses KW - Turbines Y1 - 2018 UR - http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2649209#Abstract U6 - https://doi.org/10.1115/1.4037588 SN - 0742-4795 SN - 1528-8919 VL - 140 IS - 1 SP - 012503-1 EP - 012503-11 ER - TY - GEN A1 - Kober, Markus A1 - Kühhorn, Arnold T1 - Stable implicit time-integration of flexible rotating structures—explanation for instabilities and concepts for avoidance T2 - Applied Mathematical Modelling N2 - Instabilities occurring during the implicit time-integration are still handicapping a time-efficient solution of large FEM systems of equations. Especially the simulation of flexible rotating structures is barely mastered by implicit FEM codes. For this, the Newmark algorithm and related algorithms are used for many years. Here, we derive the reasons for the mentioned inevitable numerical issues and present concepts that lead to an efficient and stable solution. KW - Nonlinear implicit time-integration KW - Instability KW - Newmark KW - Rotating structures Y1 - 2018 U6 - https://doi.org/10.1016/j.apm.2018.03.017 SN - 0307-904X VL - 60 SP - 235 EP - 243 ER - TY - GEN A1 - Beirow, Bernd A1 - Kühhorn, Arnold A1 - Figaschewsky, Felix A1 - Bornholm, Alfons A1 - Repetckii, Oleg V. T1 - Forced Response Reduction of a Blisk by Means of Intentional Mistuning T2 - Journal of Engineering for Gas Turbines and Power N2 - 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. Y1 - 2019 UR - http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2687503 U6 - https://doi.org/10.1115/1.4040715 SN - 1528-8919 SN - 0742-4795 VL - 141 IS - 1 SP - 011008-1 EP - 011008-8 ER - TY - CHAP A1 - Kober, Markus A1 - Kühhorn, Arnold A1 - Keskin, Akin T1 - Optimization of Newmark-Euler Time-Integration Parameters for a Stable and Efficient Implicit Simulation of Rotating Elastic Structures T2 - Proceedings of 15th German LS-DYNA Forum Y1 - 2018 SN - 978-3-9816215-5-6 SP - 235 EP - 238 PB - DYNAmore GmbH CY - Stuttgart ER - TY - GEN A1 - Weber, Robby A1 - Kühhorn, Arnold A1 - Heinrich, Christoph Rocky T1 - Modelling and analysis of a high-speed turbine impeller concerning mistuning T2 - The 14th International Conference of machinery (VETOMAC XIV), Lissabon, 10-13 September 2018 N2 - As-manufactured impellers behave significantly different from nominal impellers. There are no identical blades due to geometric and material deviations. In this paper three model updating procedures are discussed with the objective to achieve realistic models of as-manufactured impellers. The techniques are applied to radial inflow turbine wheel of an exhaust gas turbocharger. The first approach creates a model through optical measurement and mesh morphing. The second approach is based on a contactless measurement of blade individual vibration responses. An iterative update process gains the corresponding mistuning pattern and thus the associated model. Third, a model is found by an optimisation, that identified a mistuning pattern, that fits modal characteristics, which are evaluated during experimental modal analysis at vacuum. In-depth analyses of these models are realised to determine advantages and drawbacks of the procedures. Y1 - 2018 U6 - https://doi.org/10.1051/matecconf/201821118002 ER - TY - CHAP A1 - Figaschewsky, Felix A1 - Kühhorn, Arnold T1 - An Inverse Approach to Identify Tuned Aerodynamic Damping, System Frequencies, and Mistuning, Part 1: Theory Under Rotating Conditions T2 - Proceedings of the 15th International Symposium on Unsteady Aerodynamics, Aeroacoustics & Aeroelasticity of Turbomachines, ISUAAAT15, 24-27 September 2018, University of Oxford, UK Y1 - 2018 UR - https://www-docs.b-tu.de/fg-strukturmechanik/public/ISUAAAT15-048-Figaschewsky_Kuehhorn-SystemID_Part1.pdf PB - ISUAAAT Scientific Committee ER - TY - CHAP A1 - Beirow, Bernd A1 - Figaschewsky, Felix A1 - Kühhorn, Arnold T1 - An Inverse Approach to Identify Tuned Aerodynamic Damping, System Frequencies, and Mistuning, Part 2: Application to Blisks at Rest T2 - Proceedings of the 15th International Symposium on Unsteady Aerodynamics, Aeroacoustics & Aeroelasticity of Turbomachines, ISUAAAT15, 24-27 September 2018, University of Oxford, UK Y1 - 2018 UR - https://www-docs.b-tu.de/fg-strukturmechanik/public/ISUAAAT15-021-Beirow_Kuehhorn_Figaschewsky-SystemID_Part2.pdf PB - ISUAAAT Scientific Committee ER -