TY - CHAP A1 - Beirow, Bernd A1 - Kühhorn, Arnold A1 - Golze, Mark A1 - Parchem, Roland A1 - Johann, E. T1 - Experimentelle und numerische Untersuchungen hinsichtlich einer Festigkeitsauslegungsoptimierung von Hochdruck-Verdichter-Schaufelscheiben unter besonderer Berücksichtigung von Mistuningeffekten T2 - Deutscher Luft- und Raumfahrtkongress 2003, München, 17. bis 20. November 2003, Bd. 2 KW - Festigkeitsauslegungsoptimierung KW - Hochdruck-Verdichter-Schaufelscheiben KW - Mistuningeffekte Y1 - 2003 SP - 1495 EP - 1504 PB - DGLR CY - Bonn ER - TY - CHAP A1 - Klauke, Thomas A1 - Kühhorn, Arnold A1 - Golze, Mark A1 - Villwock, J. A1 - Lenk, Olaf T1 - Finite-Elemente-Anwendung neuerer Faserverbund-Bruchkriterien und deren Verifizierung mittels CFK-Bauteilprüfung T2 - Deutscher Luft- und Raumfahrtkongress 2003, München, 17. bis 20. November 2003, Bd. 1 KW - FEM KW - Faserverbund KW - CFK-Bauteilprüfung Y1 - 2003 SP - 113 EP - 120 PB - Dt. Ges. für Luft- und Raumfahrt CY - Bonn ER - TY - CHAP A1 - Studener, Johannes A1 - Kühhorn, Arnold T1 - FE-Simulation des thermischen Aufheizvorganges eines Silizium-Wafers im RTA (Rapid Thermal Anneal) - Prozess T2 - Tagungsband, 15. Deutschsprachige ABAQUS-Benutzerkonferenz, 22. - 23. September 2003, Fulda KW - Silizium-Wafer KW - RTA-Prozess KW - Simulation Y1 - 2003 PB - ABAQUS Deutschland GmbH CY - Aachen [u.a.] ER - TY - CHAP A1 - Kober, Markus A1 - Kühhorn, Arnold A1 - Stelldinger, Enrico A1 - Keskin, Akin T1 - Considerations About the Necessary Mesh Density of Bearings in Detailed Finite Element Models T2 - ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Volume 7B: Structures and Dynamics Düsseldorf, Germany, June 16–20, 2014, Paper GT2014-25624 N2 - In order to predict properly the behavior of very complex mechanical models, much focus needs to be done on the level of model details as well as the techniques used to predict component movements based on mechanical and thermal loads. In particular bearings and joints play a significant role in big model assemblies such as aero-engines where most of the structures are modeled by solid elements rather than using traditional shell or beam elements. This approach is very complex and expensive in terms of computational effort however can lead to increased simulation accuracy when done properly. This publication will answer questions related to the modeling techniques required for detailed bearings (not only rotor bearings) and joints of an aero-engine application where these components are not idealized or simplified, i.e. the ball in a ball joint is meshed by solid elements. The investigation will discuss the question about the number of elements needed to mesh a ball joint in such a way that a correct rotation is possible. If the mesh is too coarse, a rotation would be impossible due to the faceting of the rotating parts. It will be shown that a proper rotation depends on a correct relation between the radius of the inner ball, the gap size of the bearing and the number of nodes in the circumferential direction. For this relation an analytical formula has been derived and successfully tested at some examples. Furthermore, some finite element codes offer the possibility of smoothed contact surfaces. These options improve the situation but they might cause issues too. For this reason these smoothed contact options are also considered under the aspects mentioned above. Copyright © 2014 by Rolls-Royce Deutschland Ltd & Co KG KW - Density KW - Bearings Y1 - 2014 SN - 978-0-7918-4577-6 U6 - https://doi.org/10.1115/GT2014-25624 PB - ASME 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 - Journal of Engineering for Gas Turbines and Power 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 increases the risk of flutter at part load conditions. For this reason, intentional mistuning is employed 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. In this sense, two different series of blades have been made. However, 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 deviations is considered in numerical simulations. Moreover, the strong dependence of blade frequencies on the speed is taken into account since centrifugal stiffening effects significantly attenuate the blade-to-blade frequency difference. Focusing on the first flap mode it could be shown that a mitigation of flutter susceptibility is achieved by prescribing alternate mistuning, which indeed evokes 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. Finally, mistuning patterns could be identified featuring a tremendous increase of aerodynamic damping ratios. The robustness of the solutions could be proved by superimposing additional random mistuning. KW - Blades KW - Computer simulation KW - Damping KW - Design KW - Disks KW - Flow (Dynamics) KW - Flutter (Aerodynamics) KW - Vibration analysis Y1 - 2021 U6 - https://doi.org/10.1115/1.4049449 SN - 1528-8919 SN - 0742-4795 VL - 143 IS - 6 ER - TY - GEN A1 - Klauke, Thomas A1 - Kühhorn, Arnold A1 - Beirow, Bernd A1 - Golze, Mark T1 - Numerical Investigations of Localized Vibrations of Mistuned Blade Integrated Disks (Blisks) Y1 - 2009 ER - TY - CHAP A1 - Stelldinger, Enrico A1 - Kühhorn, Arnold A1 - Kober, Markus T1 - Otimization of a Carbon-fiber-reinforced Plastic Composite Structure using the Example of a Wing Rigger KW - Optimization KW - Composite KW - Wing Rigger Y1 - 2011 ER - TY - CHAP A1 - Beirow, Bernd A1 - Kühhorn, Arnold A1 - Nipkau, Jens T1 - An Equivalent Blisk Model Considering the Influence of the Air Flow on Blade Vibrations of a Mistuned Compressor Blisk T2 - Vibration Problems ICOVP 2011, The 10th International Conference on Vibration Problems, The 10th International Conference on Vibration Problems KW - Mistuned Compressor Blisk KW - Blade Vibrations KW - Air Flow Y1 - 2011 SN - 978-94-007-2068-8 SP - 549 EP - 555 PB - Springer CY - Berlin [u.a.] ER - TY - CHAP A1 - Nipkau, Jens A1 - Kühhorn, Arnold A1 - Beirow, Bernd T1 - Modal and Aeroelastic Analysis of a Mistuned Compressor Blisk Using an Equivalent Blisk Model KW - Blisk vibration KW - Mistuning KW - Aerodynamic Influence Coefficients Y1 - 2011 ER - TY - CHAP A1 - Beirow, Bernd A1 - Nipkau, Jens A1 - Kühhorn, Arnold T1 - Modal and Aeroelastic Analysis of a Compressor Blisk Considering Mistuning T2 - Proceedings of the ASME Turbo Expo 2011, presented at the ASME 2011 Turbo Expo, June 6 - 10, 2011, Vancouver, British Columbia, Canada, Vol. 6, part B KW - Mistuning KW - Compressor Blisk Y1 - 2011 SN - 978-0-7918-5466-2 N1 - GT2011-45849 SP - 1309 EP - 1319 PB - ASME CY - New York, NY ER - 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 -