TY - CHAP A1 - Höhnisch, Peter A1 - Kühhorn, Arnold A1 - Beirow, Bernd T1 - Experimental and Numerical Analysis of Radial Turbine Bliks with Regard to Mistuning KW - Tadial KW - Turbine KW - Vibration KW - Mistuning KW - Model Update Y1 - 2011 ER - TY - GEN A1 - Heinrich, Christoph Rocky A1 - Kühhorn, Arnold A1 - Steff, Klaus A1 - Petry, Nico T1 - Generalized Model for the Approximation of Coupled Acousto-Mechanical Natural Frequencies in High-Pressure Centrifugal Compressors T2 - Journal of Engineering for Gas Turbines and Power N2 - The oil and gas, chemical, and process industries employ centrifugal compressors for a wide range of applications. Due to this, the conditions under which centrifugal compressors have to operate, vary significantly from case to case. Gas pipeline compressors, for example, may feature discharge pressures well over 100 bar. During the last decades, comprehensive research was conducted on the impact of high pressure operating conditions on the vibrational behavior of centrifugal compressors. Nowadays, it is well-known that an increase in gas pressure levels leads to a more pronounced interaction between the side cavities and the impeller, which results in a frequency shift of the acoustic and structural modes. For the safe operation of compressors, it is necessary to predict these coupled natural frequencies accurately. The state-of-the-art approach to achieve this objective is the finite element method. While this technique provides high-quality results, it incurs high computational costs and is, therefore, time-consuming. The authors of the current paper propose a generalized model to overcome this challenge. It uses the uncoupled modes of the impeller and side cavities in a modal superposition to approximate the coupled system's natural frequencies. In this way, the intended design geometries are considered while reducing the computational effort significantly. In a numerical study, the generalized model is applied to different systems of increasing complexity, and the results are compared to a finite element analysis. Finally, the paper concludes with a discussion of the limitations and benefits of all employed numerical methods. KW - Approximation KW - Compressors KW - High pressure (Physics) KW - Cavities KW - Impellers KW - Acoustics KW - Finite element methods KW - Numerical analysis Y1 - 2020 U6 - https://doi.org/10.1115/1.4049447 SN - 1528-8919 ER - TY - CHAP A1 - Kühhorn, Arnold A1 - Beirow, Bernd A1 - Strehlau, Ulrik T1 - Zum Schwingungsverhalten integraler Hochdruckverdichterlaufräder Y1 - 2009 ER - TY - GEN A1 - Gambitta, Marco A1 - Kühhorn, Arnold A1 - Beirow, Bernd A1 - Schrape, Sven T1 - Stator Blades Manufacturing Geometrical Variability in Axial Compressors and Impact on the Aeroelastic Excitation Forces T2 - Journal of Turbomachinery N2 - The manufacturing geometrical variability is a source of uncertainty, which cannot be avoided in the realization of machinery components. Deviations of a part geometry from its nominal design are inevitably present due to the manufacturing process. In the case of the aeroelastic forced response problem within axial compressors, these uncertainties may affect the vibration characteristics. For this reason, the impact of geometrical uncertainties due to the manufacturing process onto the modal forcing of axial compressor blades is investigated in this study. The research focuses on the vibrational behavior of an axial compressor rotor blisk. In particular, the amplitude of the forces acting as a source of excitation on the vibrating blades is studied. The geometrical variability of the upstream stator is investigated as input uncertainty. The variability is modeled starting from a series of optical surface scans. A stochastic model is created to represent the measured manufacturing geometrical deviations from the nominal model. A data reduction methodology is proposed in order to represent the uncertainty with a minimal set of variables. The manufacturing geometrical variability model allows to represent the input uncertainty and probabilistically evaluate its impact on the aeroelastic problem. An uncertainty quantification is performed in order to evaluate the resulting variability on the modal forcing acting on the vibrating rotor blades. Of particular interest is the possible rise of low engine orders due to the mistuned flow field along the annulus. A reconstruction algorithm allows the representation of the variability during one rotor revolution. The uncertainty on low harmonics of the modal rotor forcing can be therefore identified and quantified. KW - aeromechanical instabilities KW - computational fluid dynamics (CFD) KW - turbomachinery blading design Y1 - 2022 U6 - https://doi.org/10.1115/1.4052602 SN - 1528-8900 VL - 144 ER - TY - CHAP A1 - Springmann, Marcel A1 - Kühhorn, Arnold A1 - Rauer, Georg A1 - Giersch, Thomas T1 - Constitutive Modelling of Plastic and Creep Behavior of the Nickel Base Superalloy ALLVAC® 718PLUS® under Heat Treatment Conditions KW - Behavior KW - Nickel-Based Superalloy KW - Heat Treatment Conditions Y1 - 2011 ER - TY - CHAP A1 - Hönisch, Peter A1 - Kühhorn, Arnold T1 - Mistuning und Dämpfung von Radialturbinen KW - Mistuning KW - Dämpfung KW - Radialturbine Y1 - 2011 ER - TY - GEN A1 - Hanschke, Benjamin A1 - Kühhorn, Arnold A1 - Schrape, Sven A1 - Giersch, Thomas T1 - Consequences of Borescope Blending Repairs on Modern HPC Blisk Aeroelasticity T2 - Journal of Turbomachinery N2 - Objective of this paper is to analyze the consequences of borescope blending repairs on the aeroelastic behavior of a modern high pressure compressor (HPC) blisk. To investigate the blending consequences in terms of aerodynamic damping and forcing changes, a generic blending of a rotor blade is modeled. Steady-state flow parameters like total pressure ratio, polytropic efficiency, and the loss coefficient are compared. Furthermore, aerodynamic damping is computed utilizing the aerodynamic influence coefficient (AIC) approach for both geometries. Results are confirmed by single passage flutter (SPF) simulations for specific interblade phase angles (IBPA) of interest. Finally, a unidirectional forced response analysis for the nominal and the blended rotor is conducted to determine the aerodynamic force exciting the blade motion. The frequency content as well as the forcing amplitudes is obtained from Fourier transformation of the forcing signal. As a result of the present analysis, the change of the blade vibration amplitude is computed. Y1 - 2019 U6 - https://doi.org/10.1115/1.4041672 SN - 1528-8900 SN - 0889-504X VL - 141 IS - 2 ER - TY - CHAP A1 - Kühhorn, Arnold A1 - Beirow, Bernd A1 - Parchem, Roland A1 - Klauke, Thomas T1 - Schaufelschwingungen bei realen Verdichter-Integralrädern (BLISK) T2 - Deutscher Luft- und Raumfahrtkongress 2006, Braunschweig, 06. bis 09. November 2006, Bd. 2 KW - Schaufelschwingungen KW - Blisk Y1 - 2006 SP - 1199 EP - 1208 PB - Dt. Ges. für Luft- und Raumfahrt CY - Bonn ER - TY - GEN A1 - Gambitta, Marco A1 - Kühhorn, Arnold A1 - Beirow, Bernd A1 - Schrape, Sven T1 - Stator Blades Manufacturing Geometrical Variability in Axial Compressors and Impact on the Aeroelastic Excitation Forces T2 - Proceedings of ASME Turbo Expo 2021, ASME Paper Number: GT2021-59642 N2 - The manufacturing geometrical variability is a source of uncertainty, which cannot be avoided in the realization of a machinery. Deviations of a component geometry from its nominal design are inevitably present due to the manufacturing process. In the case of the aeroelastic forced response problem within axial compressors, these uncertainties may affect the vibration characteristics. For this reason, the impact of geometrical uncertainties due to the manufacturing process onto the modal forcing of axial compressor blades is investigated in this study. The research focuses on the vibrational behavior of an axial compressor rotor blisk (blade-integrated disk) and in particular the amplitude of the forces acting as source of excitation on the vibrating blades (modal forcing). Within this context, the geometry of the upstream stator plays an important role as in general the main harmonics of the rotor excitation forces are produced by its wake. Therefore, small variations of the upstream stators geometries, such as the ones caused by the manufacturing process, may affect the resulting forcing. In particular, the geometrical variability of the upstream stator implies that the hypothesis of a cyclic-symmetrical flow is no longer valid. This may cause the introduction of lower harmonic components in the modal forces, generally referred to as Low Engine Orders (LEO). The geometrical variability is modelled starting from a series of optical surface scans. A set of optical measurements of manufactured stator blades originating from the same nominal design constitutes the baseline dataset on which the geometrical model is built. The measured blades as well as the relative nominal geometry are parametrized to describe the individual blades surfaces. The parameterization is accomplished by slicing the surfaces in radial sections and describing each of these with a set of NACA-like parameters [1]. The measured geometrical deviations from the nominal model can therefore be described as an offset of such parameters. A reduced representation of the variables representing the input uncertainty (noise variables) is obtained via Principal Components Analysis. Afterwards a sampling on the reduced noise variables domain can be done to represent the modelled uncertainty and perform an Uncertainty Quantification (UQ) on the relative quantities of interest, in this case the modal forcing. The computation of the modal forcing is done through a CFD solver, computing the unsteady flow field around the rotor blades. The domain considered in this case is a 1.5 stage of the axial compressor, including the rotor and the up- and down-stream stators. The solutions are initialized from a validated steady state solution of the considered compressor rig. The time-dependent pressure field calculated on the rotor blades is projected onto the relative vibrational mode shapes of interests (from structural modal analyzes). The resulting forces are analyzed by means of their spectrum, evaluating the amplitudes for the present engine orders (higher harmonics of the shaft mechanical speed). The UQ uses Monte Carlo methods to evaluate the impact of the geometrical variability onto the modal forcing. The modelled uncertainty on the geometries is introduced into the CFD solver to compute the deviations on the quantities of interest. A reconstruction of the forces acting on the rotor during one revolution is obtained. This allows to evaluate the uncertainty on the present engine orders as well as the possible rise of LEO for the rotor blades in presence of a mistuned upstream stator. [1]: Lange A., Vogeler K., Gümmer V., Schrapp H. and Clemen C. (2009). “Introduction of a Parameter Based Compressor Blade Model for Considering Measured Geometry Uncertainties in Numerical Simulation.” Proceedings of ASME Turbo Expo. GT2009-59937 Y1 - 2021 UR - https://asme-turboexpo.secure-platform.com/a/solicitations/137/sessiongallery/6794/application/59642 ER - TY - CHAP A1 - Nipkau, Jens A1 - Kühhorn, Arnold A1 - Schrape, S. T1 - Determination of Aeroelastic Parameters of a High-Pressure-Compressor Stage using Fluid-Structure Interaction Calculations T2 - Seminar: Simulation of Complex Flows (CFD), applications and trends, 10th - 11th March 2008, Wiesbaden, Germany Y1 - 2008 SN - 978-1-87437-633-0 PB - NAFEMS Contact DACH & Nordic Countries CY - Bernau am Chiemsee ER - TY - GEN A1 - Naveed, Zishan A1 - Kühhorn, Arnold T1 - An Isogeometric Based Study of Contact Behaviour for Rotating Structures T2 - 14th World Congress on Computational Mechanics (WCCM)-ECCOMAS Congress 2020, Virtual Conference: 11-15 January 2021 Y1 - 2021 UR - https://www.b-tu.de/fg-strukturmechanik/publikationen/veroeffentlichungen-und-vortraege ER - TY - CHAP A1 - Schrape, S. A1 - Kühhorn, Arnold A1 - Golze, Mark T1 - Simulation fluidgedämpfter Strukturschwingungen durch partitionierte Fluid-Struktur-Kopplung mittels MpCCI KW - Fluid-Struktur-Kopplung Y1 - 2006 ER - TY - JOUR A1 - Schrape, S. A1 - Kühhorn, Arnold A1 - Golze, Mark T1 - Simulation fluidgedämpfter Strukturschwingungen mittels partitioniertem Kopplungssatz via MpCCI JF - NAFEMS-Magazin KW - fluidgedämpfte Strukturschwingungen Y1 - 2006 VL - 2 IS - 4 SP - 41 EP - 49 ER - TY - CHAP A1 - Schrape, S. A1 - Kühhorn, Arnold A1 - Golze, Mark T1 - Simulation of fluid damped structural vibrations T2 - Proceedings, 7th MpCCI User Forum, February 21st and 22nd 2006, at Schloss Birlinghoven, Sankt Augustin, Germany KW - fluid structures Y1 - 2006 SP - 112 EP - 121 CY - Sankt Augustin ER - TY - CHAP A1 - Strehlau, Ulrik A1 - Kühhorn, Arnold T1 - Experimental and numerical investigations of HPC blisks with a focus on travelling waves T2 - Proceedings of the ASME Turbo Expo 2010, presented at the 2010 ASME Turbo Expo, June 14 - 18, 2010, Glasgow, UK, Volume 6, part B Y1 - 2010 SN - 978-0-7918-4401-4 N1 - GT2010-22463 SP - 865 EP - 878 PB - ASME CY - New York, NY ER - TY - GEN A1 - Maywald, Thomas A1 - Beirow, Bernd A1 - Kühhorn, Arnold T1 - Mistuning und Dämpfung von Radialturbinenrädern T2 - MTZ - Motortechnische Zeitschrift N2 - Moderne Verbrennungskraftmaschinen müssen ein stetig wachsendes Anforderungsprofil in Bezug auf Wirtschaftlichkeit, Leistung und Umweltfreundlichkeit erfüllen. In diesem Zusammenhang hat die Turboaufladung von Verbrennungsmotoren an Bedeutung gewonnen. Bei Turboladern kleiner und mittlerer Baugröße, deren Turbinen einen Durchmesser zwischen 30 und 250 mm aufweisen, kommen vornehmlich gegossene Laufräder zum Einsatz. Am Institut für Verkehrstechnik der Brandenburgischen Technischen Universität Cottbus-Senftenberg wurde im Rahmen eines FVV-Forschungsvorhabens der Einfluss charakteristischer Betriebsgrößen eines Turboladers auf das strukturdynamische Verhalten solcher Radialturbinenräder untersucht. Y1 - 2015 U6 - https://doi.org/10.1007/s35146-015-0043-7 SN - 2192-8843 VL - 76 IS - 06 SP - 68 EP - 75 ER - TY - GEN A1 - Beirow, Bernd A1 - Kühhorn, Arnold A1 - Weber, Robby A1 - Popig, Frederik T1 - Vibration Analyses of an Axial Turbine Wheel With Intentional Mistuning T2 - Turbo Expo 2020, Virtual Conference, Virtual Conference and Exhibition, Online, September 21 – 25, 2020 N2 - The last stage bladed disk of a steam turbine is analyzed with respect to both flutter susceptibility and limitation of forced response. Due to the lack of variable stator vanes unfavorable flow conditions may occur which can lead to flow separation in some circumstances. Consequently, there is the risk of flutter in principle, particularly at nominal speed under part load conditions. For this reason, intentional mistuning is employed by the manufacturer with the objective to prevent any self-excited vibrations. A first step in this direction is done by choosing alternate mistuning, which keeps the manufactural efforts in limits since only two different blade designs are allowed. In this sense, two different series of blades have been made. However, it is well known that small deviations from the design intention are unavoidable due to the manufacturing procedure, which could be proved by bonk tests carried out earlier. The influence of these additional but unwanted deviations is considered in numerical simulations. Moreover, the strong dependence of blade frequencies on the speed is taken into account since it significantly attenuates the blade to blade frequency difference in this particular case. Within an academic study the turbine wheel is modelled as blade integrated disk in order to demonstrate fundamental effects of intentional mistuning on flutter susceptibility and forced response. For that purpose, reduced order models are built up by using the subset of nominal system mode approach introduced by Yang and Griffin [1], which conveniently allows for taking into account both differing mistuning patterns and the impact of aeroelastic interaction. Focusing on the first flap mode it could be shown that a mitigation of flutter susceptibility is achieved by prescribing alternate mistuning, which indeed affects an increase of originally small aerodynamic damping ratios. Nevertheless, the occurrence of negative damping ratios could not be completely precluded at part load conditions. That is why optimization studies are conducted based on genetic algorithms with the objective function of maximizing the lowest aerodynamic damping ratios. Again only two different blade designs are admitted. Finally, mistuning patterns could be identified causing a tremendous increase of aerodynamic damping ratios. The robustness of the solutions found could be proved by superimposing additional random mistuning. Another study is focused on the impact of mistuning strength. Further analyses are addressing the forced response at part speed conditions, where different resonance crossings are becoming apparent in the Campbell plot. An increase of the forced response compared to the tuned counterpart is partly unpreventable because of unfavorable aerodynamic damping curves. Independently, the maximum forced response has to be limited also in case of applying large intentional mistuning. [1] Yang, M. T., Griffin, J. H., „A Reduced-Order model of Mistuning Using a Subset of Nominal System Modes“. J Eng Gas Turb Power, 123, pp. 893-900 (2001). Y1 - 2020 UR - https://asme-turboexpo.secure-platform.com/a/solicitations/105/sessiongallery/5325/application/45830 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 - 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 - 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 -