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 - TY - GEN 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 - Journal of Sound and Vibration N2 - With the objective of attenuating 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 resulting in a forced response clearly below that of the tuned counterpart. 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 actually manufactured mistuning 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. Finally, the robustness of the gain achieved with intentional mistuning could be proved towards both additional but unavoidable random structural and aerodynamic mistuning. KW - Balde integradet disk KW - Intentional mistuning KW - Vibration KW - Forced response KW - Optimization Y1 - 2019 U6 - https://doi.org/10.1016/j.jsv.2018.10.064 SN - 0022-460X VL - 442 SP - 11 EP - 27 ER - TY - GEN A1 - Figaschewsky, Felix A1 - Hanschke, Benjamin A1 - Kühhorn, Arnold T1 - Efficient Generation of Engine Representative Tip Timing Data Based on a Reduced Order Model for Bladed Rotors T2 - Journal of Engineering for Gas Turbines and Power KW - Vibration KW - Blades KW - Deflection KW - Engines KW - Probes KW - Signals KW - Rotors KW - Uncertainty KW - Errors KW - Simulation Y1 - 2018 U6 - https://doi.org/10.1115/1.4040748 SN - 0742-4795 SN - 1528-8919 VL - 141 IS - 1 ER - TY - CHAP A1 - Koch, Ilja A1 - Beirow, Bernd A1 - Filippatos, Angelos A1 - Kühhorn, Arnold A1 - Gude, Maik T1 - Methodical Approach for Simulation the Vibration of Damaged Fibre Reinforced Composite Rotors Under Consideration of Aerodynamic Influences T2 - 18th European Conference on Composite Materials (ECCM18), Athen (Griechenland), 25.-28. Juni 2018 Y1 - 2018 UR - https://pcoconvin.eventsair.com/QuickEventWebsitePortal/eccm/program/Agenda/AgendaItemDetail?id=258960e5-a867-4c02-b01e-4c997026cf20 ER - TY - GEN A1 - Figaschewsky, Felix A1 - Hanschke, Benjamin A1 - Kühhorn, Arnold T1 - Efficient Generation of Engine Representative Tip Timing Data Based on a Reduced Order Model for Bladed Rotors T2 - ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition, Volume 7C: Structures and Dynamics, Oslo, Norway, June 11–15, 2018 N2 - In modern compressors the assessment of blade vibration levels as well as health monitoring of the components are fundamental tasks. Traditionally, this assessment is done by the application of strain gauges to some blades of the assembly. In contrast to strain gauges, blade tip timing (BTT) offers a contactless monitoring of all blades of a rotor and there is no need of a telemetry system. A major issue in the interpretation of BTT data is the heavily undersampled nature of the signal. Usually, newly developed BTT algorithms are tested with sample data created by simplified structural models neglecting many of the uncertainties and disturbing influences of real applications. This work focuses on the creation of simulated BTT datasets as close as possible to real case measurements. For this purpose a subset of nominal system modes (SNM) representation of a compressor rotor is utilized. This model is able to include a large number of features present in real measurements, such as mistuning, static blade deflections due to centrifugal loads, aerodynamic damping and multiple mode resonances. Additionally, manufacturing deviations of the blade geometry, probe positioning errors in the BTT system and noise in the time of arrivals (TOAs) are captured by the BTT simulation environment. The main advantage of the created data is the possibility to steadily increase the signal complexity. Starting with a “perfect” signal the simulation environment is able to add different uncertainties one after the other. This allows the assessment of the influence of different features occurring in real measurements on the performance and accuracy of the analysis algorithms. Finally, a comparison of simulated BTT data and real data acquired from a rig test is shown to validate the presented approach of BTT data generation. Copyright © 2018 by Rolls-Royce Deutschland Ltd & Co KG KW - Engines KW - Rotors Y1 - 2018 SN - 978-0-7918-5115-9 U6 - https://doi.org/10.1115/GT2018-76342 PB - ASME CY - New York, NY ER - TY - CHAP 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 - ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition, Volume 7C: Structures and Dynamics, Oslo, Norway, June 11–15, 2018 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. KW - Engines KW - Manufactoring KW - Simulation KW - Turbochargers KW - Damping KW - Optimization Y1 - 2018 SN - 978-0-7918-5115-9 U6 - https://doi.org/10.1115/GT2018-76584 PB - ASME CY - New York, NY ER - TY - GEN A1 - Weber, Robby A1 - Kühhorn, Arnold T1 - Mistuning Identification Approach With Focus on High-Speed Centrifugal Compressors T2 - ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition, Volume 7C: Structures and Dynamics, Oslo, Norway, June 11–15, 2018 N2 - Blade vibrations are one of the main cost drivers in turbo-machinery. Computational blade vibration analysis facilitates an enormous potential to increase the productivity in the design of bladed components. Increasing computing power as well as improved modeling and simulation methods lead to comprehensive calculation results. This allows for a more precise prediction and assessment of experimental data. Usually, in the field of turbomachinery, identical blades are assumed to lower the required computational resources. However, mistuning is unavoidable, since small deviations due to the manufacturing process will lead to slightly different blade behavior. Potential effects such as mode localization and amplification can be treated statistically and have been thoroughly studied in the past. Since then, several reduced order models (ROMs) have been invented in order to calculate the maximum vibration amplitude of a fleet of mistuned blisks. Most commonly, mistuning is thereby modeled by small material deviations from blade to blade, e.g. Young’s modulus or density. Nowadays, it is common knowledge that the level of manufacturing imperfection (referred as level of mistuning) significantly influence mode localization as well as vibration amplification effects. Optical measurements of the geometric deviations of manufactured blades and converting to a high-fidelity finite element model make huge progress. However, to the knowledge of the authors, there is no reliable method, that derives a characteristic quantity from the geometric mistuning, that fits into the mentioned statistically approaches. Therefore, experimental data is needed to quantify the level of mistuning. Several approaches, which isolate blade individual parameters, are used to identify the dynamic behavior of axial compressors and turbines. These methods can be applied to medium-speed centrifugal turbine wheels but tend to fail to evaluate high-speed compressor with splitter blades. This paper briefly presents the original approach and discusses the reasons for failure. Thereafter, a new approach is proposed. Finally the level of mistuning and important quantities to perform a statistical evaluation of a high-speed compressor is shown. Copyright © 2018 by ASME KW - Compressors Y1 - 2018 SN - 978-0-7918-5115-9 U6 - https://doi.org/10.1115/GT2018-75382 PB - ASME CY - New York, NY ER - TY - GEN A1 - Wagner, Frank A1 - Kühhorn, Arnold A1 - Janetzke, Timm A1 - Gerstberger, Ulf T1 - Multi-Objective Optimization of the Cooling Configuration of a High Pressure Turbine Blade T2 - ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition, Volume 5C: Heat Transfer Oslo, Norway, June 11–15, 2018 N2 - Due to the increasing turbine inlet temperature and in order to improve the overall efficiency it is necessary to optimize the cooling design of the hot gas components of an aero engine. The current paper discusses the strategy of optimizing a rotor blade cooling configuration of a small civil aero engine, comprising of films and internal turbulators (ribs). An insight into the parametrization is given including the location of the films and ribs as well as the number of the films and ribs. The parameter reduction results in 18 input parameters for the optimizations to limit the number of parameters to an acceptable level. Two optimizations are carried out with the primary objectives of non-dimensional mass flow and overall cooling effectiveness. Different optimization algorithms are used, namely AMGA and NSGA-II, and compared afterwards. A further optimization is carried out with direct objectives of mass flow and mean surface temperature using the AMGA algorithm. The outputs from the optimizations are presented as a pareto-front. These plots are used for a comparison of the optimization algorithms and formulations respectively. Finally, the differences are discussed and the advantages and disadvantages of the algorithms used are highlighted. Copyright © 2018 by Rolls-Royce Deutschland Ltd & Co KG KW - Cooling KW - Turbine Blades KW - High Pressure (Physics) KW - Pareto Optimization Y1 - 2018 SN - 978-0-7918-5110-4 U6 - https://doi.org/10.1115/GT2018-75616 PB - ASME CY - New York, NY ER - TY - CHAP A1 - Weber, Robby A1 - Kühhorn, Arnold T1 - Mistuning und Dämpfung radialer Turbinen- und Verdichterlaufräder T2 - Abschluss- und Zwischenberichte der Forschungsstellen Turbomaschinen, Frühjahrstagung 2018, Tagungsband 2018, Bad Neuenahr Y1 - 2018 SP - 159 EP - 190 PB - Forschungsvereinigung Verbrennungskraftmaschinen e.V. CY - Frankfurt am Main ER - TY - CHAP A1 - Kober, Markus A1 - Kühhorn, Arnold A1 - Keskin, Akin T1 - Instability problems in implicit transient FEM simulations of fast rotating elastic structures - Description of the phenomenon and possible solutions T2 - Proceedings of NAFEMS DACH Conference 2018, Bamberg, May 14-16, 2018 Y1 - 2018 SN - 978-1-910643-14-3 SP - 48 EP - 52 PB - NAFEMS Deutschland, Österreich, Schweiz GmbH CY - Grafing ER - TY - GEN A1 - Weber, Robby A1 - Kühhorn, Arnold T1 - Mistuning Identification Approach With Focus on High-Speed Centrifugal Compressors T2 - Journal of Engineering for Gas Turbines and Power KW - Compressors KW - Blades KW - Vibration Y1 - 2019 U6 - https://doi.org/10.1115/1.4040999 SN - 1528-8919 SN - 0742-4795 VL - 14 IS - 3 ER - TY - GEN A1 - Kober, Markus A1 - Kühhorn, Arnold A1 - Keskin, Akin T1 - Instabilitätsprobleme bei der impliziten transienten FEM-Simulation schnell rotierender elastischer Strukturen – Beschreibung des Phänomens und Lösungsmöglichkeiten T2 - NAFEMS-Online-Magazin Y1 - 2018 SN - 2311-522X N1 - Download des jeweils aktuellen Hefts: https://www.nafems.org/publications/magazin/ VL - 48 IS - 4 SP - 36 EP - 49 ER - TY - GEN A1 - Henke, Anna-Sophia A1 - Noack, Martin A1 - Geyer, Thomas A1 - Heinrich, Christoph Rocky A1 - Beirow, Bernd A1 - Sarradj, Ennes A1 - Kühhorn, Arnold T1 - Calculation of the Modal Behavior of Structured Sheet Metal T2 - International Journal of Lightweight Materials and Manufacture Y1 - 2019 U6 - https://doi.org/10.1016/j.ijlmm.2019.01.004 SN - 2588-8404 ER - TY - GEN A1 - Beirow, Bernd A1 - Kühhorn, Arnold A1 - Figaschewsky, Felix A1 - Hönisch, Peter A1 - Giersch, Thomas A1 - Schrape, Sven T1 - Model update and validation of a mistuned high-pressure compressor blisk T2 - The Aeronautical Journal N2 - In order to prepare an advanced 4-stage high-pressure compressor rig test campaign, details regarding both accomplishment and analysis of preliminary experiments are provided in this paper. The superior objective of the research project is to contribute to a reliable but simultaneously less conservative design of future high pressure blade integrated disks (blisk). It is planned to achieve trend-setting advances based on a close combination of both numerical and experimental analyses. The analyses are focused on the second rotor of this research compressor, which is the only one being manufactured as blisk. The comprehensive test program is addressing both surge and forced response analyses e.g. caused by low engine order excitation. Among others the interaction of aeroelastics and blade mistuning is demanding attention in this regard. That is why structural models are needed, allowing for an accurate forced response prediction close to reality. Furthermore, these models are required to support the assessment of blade tip timing (BTT) data gathered in the rig tests and strain gauge (s/g) data as well. To gain the maximum information regarding the correlation between BTT data, s/g-data and pressure gauge data, every blade of the second stage rotor (28 blades) is applied with s/g. However, it is well known that s/g on blades can contribute additional mistuning that had to be considered upon updating structural models. Due to the relevance of mistuning, efforts are made for its accurate experimental determination. Blade-by-blade impact tests according to a patented approach are used for this purpose. From the research point of view, it is most interesting to determine both the effect s/g-instrumentation and assembling the compressor stages on blade frequency mistuning. That is why experimental mistuning tests carried out immediately after manufacturing the blisk are repeated twice, namely, after s/g instrumentation and after assembling. To complete the pre-test program, the pure mechanical damping and modal damping ratios dependent on the ambient pressure are experimentally determined inside a pressure vessel. Subsequently the mistuning data gained before is used for updating subset of nominal system mode (SNM) models. Aerodynamic influence coefficients (AICs) are implemented to take aeroelastic interaction into account for forced response analyses. Within a comparison of different models, it is shown for the fundamental flap mode (1F) that the s/g instrumentation significantly affects the forced response, whereas the impact of assembling the compressor plays a minor role. KW - Blisk KW - Mistuning KW - Aerodynamic damping Y1 - 2019 U6 - https://doi.org/10.1017/aer.2018.149 SN - 2059-6464 SN - 0001-9240 VL - 123 IS - 1260 SP - 230 EP - 247 ER - TY - GEN A1 - Figaschewsky, Felix A1 - Kühhorn, Arnold A1 - Beirow, Bernd A1 - Giersch, Thomas A1 - Schrape, Sven T1 - Analysis of mistuned forced response in an axial high-pressure compressor rig with focus on Tyler–Sofrin modes T2 - The Aeronautical Journal N2 - This paper aims at contributing to a better understanding of the effect of Tyler–Sofrin Modes (TSMs) on forced vibration responses by analysing a 4.5-stage research axial compressor rig. The first part starts with a brief review of the involved physical mechanisms and necessary prerequisites for the generation of TSMs in multistage engines. This review is supported by unsteady CFD simulations of a quasi 2D section of the studied engine. It is shown that the amplitude increasing effect due to mistuning can be further amplified by the presence of TSMs. Furthermore, the sensitivity with respect to the structural coupling of the blades and the damping as well as the shape of the expected envelope is analysed. The second part deals with the Rotor 2 blisk of the research compressor rig. The resonance of a higher blade mode with the engine order of the upstream stator is studied in two different flow conditions realised by different variable stator vane (VSV) schedules which allows to separate the influence of TSMs from the impact of mistuning. A subset of nominal system modes representation of the rotor is used to describe its mistuned vibration behaviour, and unsteady CFD simulations are used to characterise the present strength of the TSMs in the particular operating conditions. Measured maximum amplitude vs blade pattern and frequency response functions are compared against the predictions of the aeromechanical models in order to assess the strength of the TSMs as well as its influence on vibration levels. Y1 - 2019 U6 - https://doi.org/10.1017/aer.2018.163 SN - 2059-6464 IS - 123 SP - 356 EP - 377 ER - TY - GEN A1 - Weber, Robby A1 - Kühhorn, Arnold T1 - Mistuning und Dämpfung radialer Turbinen- und Verdichterlaufräder T2 - Abschluss- und Zwischenberichte der Forschungsstellen Turbomaschinen : Frühjahrstagung 2019 : Tagungsband : 2019 - Würzburg T2 - Final and interim reports presented by the RTD performers Turbomachinery : FFV 2019 Spring conference : proceedings / N2 - Abschlussbericht zum FVV-Projekt Mistuning und Dämpfung III Y1 - 2019 SP - 75 EP - 109 PB - Forschungsvereinigung Verbrennungskraftmaschinen e.V. CY - Frankfurt am Main ER - TY - GEN A1 - Naveed, Zishan A1 - Kühhorn, Arnold A1 - Kober, Markus T1 - Comparative Evaluation of Isogeometric Analysis and Classical FEM with Regard to Contact Anaylsis T2 - 12th European LS-DYNA Conference 2019, 14-16 May 2019, Koblenz N2 - Isogeometric analysis represents a newly developed technique that offers the application of Computer Aided Designs (CAD) concept of Non-uniform Rational B-Splines (NURBS) tool to describe the geometry of the computational domain. The simplified transition of CAD models into the computational domain eliminates the problems arising from the geometrical discontinuities induced by the faceted approximation of the mesh. Moreover, numerical analysis directly on NURBS objects significantly reduces the design-to-analysis time compared to traditional FEA approach. In the field of contact mechanics, when finite elements are applied to geometry with curved surfaces, the result is a non-smooth geometrical representation of interface surfaces which may lead to mesh interlocking, high jumps and spurious oscillations in contact forces. To eliminate these issues, various surface smoothening strategies are to be employed in case of FEM. Isogeometric based analysis alleviates these issues without employing any additional smoothening strategy due to inherent higher order continuity of NURBS basis functions and much more accurate results are obtained compared to conventional FE approach. In the current study, LS-DYNA is used to demonstrate the capabilities and advantage of an isogeometric analysis though an example of pendulum under gravitational load. The numerical simulation results are analytically validated and the comparison of NURBS surfaces with faceted surfaces is carried out to investigate the accuracy. Y1 - 2019 UR - https://www.dynalook.com/conferences/12th-european-ls-dyna-conference-2019/isogeometric/naveed_btu.pdf ER - TY - GEN A1 - Weber, Robby A1 - Kühhorn, Arnold A1 - Beirow, Bernd T1 - Mistuning und Dämpfung radialer Turbinen- und Verdichterlaufräder T2 - MTZ - Motortechnische Zeitschrift N2 - Turbolader tragen erheblich zur Steigerung des Motorenwirkungsgrads bei. Rotierende Komponenten sind infolge der Fliehkraft, der zur Aufladung notwendigen Strömungsumlenkungen, der instationären Druckschwankungen der Strömung sowie von Temperaturgradienten als hochbelastete Laufräder einzustufen, die unter erheblicher Schwingungsanfälligkeit leiden. Am Lehrstuhl Strukturmechanik und Fahrzeugschwingungen der BTU Cottbus-Senftenberg wurde im Rahmen eines FVV-Forschungsvorhabens der Einfluss der fertigungsbedingten Toleranzen auf eben jenes Schwingungsverhalten untersucht. Es wird nachgewiesen, dass Intentional Mistuning zu signifikant niedrigeren Belastungen führen kann. KW - Mistuning KW - Dämpfung KW - Turbinen KW - Laufräder Y1 - 2019 U6 - https://doi.org/10.1007/s35146-019-0094-2 SN - 0024-8525 SN - 2192-8843 VL - 80 IS - 9 SP - 74 EP - 78 ER - TY - GEN A1 - Weber, Robby A1 - Kühhorn, Arnold A1 - Beirow, Bernd T1 - Mistuning and Damping of Turbine and Compressor Impellers T2 - MTZ worldwide N2 - Turbocharging is known to be a well-established technology for an engine's efficiency and power output by forcing extra compressed air into the combustion chamber. The centrifugal loads, necessary flow deflections, unsteady pressure fluctuations, and structural temperature gradients put a high strain on rotating components. Additionally, those components are prone to high-cycle fatigue. The Chair of Structural Mechanics and Vehicle Vibrational Technology at the BTU Cottbus-Senftenberg investigated the impact of manufacturing tolerances on the vibrational behavior of several turbine and compressor impellers. Finally, it is shown that intentional mistuning can lead to significantly lower stresses. KW - Mistuning KW - Damping KW - Compressor Impellers Y1 - 2019 U6 - https://doi.org/10.1007/s38313-019-0090-4 SN - 2192-9114 VL - 80 IS - 9 SP - 72 EP - 77 ER -