TY - CHAP A1 - Keskin, Akin A1 - Swoboda, Marius A1 - Flassig, Peter Michael A1 - Dutta, Amit Kumar A1 - Bestle, Dieter T1 - Accelerated Industrial Blade Design Based on Multi-Objective Optimization Using Surrogate Model Methodology T2 - Proceedings of the ASME Turbo Expo 2008, presented at the 2008 ASME Turbo Expo, June 9 - 13, 2008, Berlin, Germany, Vol 6., Part C KW - Optimization KW - Blade Design Y1 - 2008 SN - 978-0-7918-4316-1 SP - 2339 EP - 2349 PB - ASME CY - New York, NY ER - TY - CHAP A1 - Keskin, Akin A1 - Dutta, Amit Kumar A1 - Bestle, Dieter T1 - Modern Compressor Aerodynamic Blading Process using Multi-objective Optimization T2 - Proceedings of the ASME Turbo Expo 2006, presented at the 2006 ASME Turbo Expo, May 6 - 11, 2006, Barcelona, Spain, Vol. 6, Part B Y1 - 2006 SN - 0-7918-4241-X SP - 1209 EP - 1216 PB - ASME CY - New York, NY ER - TY - CHAP A1 - Keskin, Akin A1 - Bestle, Dieter T1 - A Method for Using Multi-objective Optimization within the Rolls-Royce meanline Prediction Process Y1 - 2005 ER - TY - CHAP A1 - Dutta, Amit Kumar A1 - Flassig, Peter Michael A1 - Bestle, Dieter A1 - Keskin, Akin A1 - Swoboda, Marius T1 - Validierung optimierter Verdichterschaufeln mit Hilfe der 3D-CFD T2 - Deutscher Luft- und Raumfahrtkongress 2008, Darmstadt, 23. bis 25. September 2008, Bd. 2 Y1 - 2008 N1 - DLRK 2008-081222 SP - 1023 EP - 1033 PB - Dt. Ges. für Luft- und Raumfahrt CY - Bonn ER - TY - CHAP A1 - Keskin, Akin A1 - Przewozny, Hans A1 - Gräsel, Jürgen A1 - Saxer, Andre A1 - Swoboda, Marius T1 - A full parametric model for turbo machinery blade design and optimisation Y1 - 2004 ER - TY - CHAP A1 - Bestle, Dieter A1 - Keskin, Akin A1 - Otto, Dierk T1 - Process Integration and Automation for optimal Design Y1 - 2006 ER - TY - CHAP A1 - Kober, Markus A1 - Kühhorn, Arnold A1 - Kästner, Benjamin A1 - Keskin, Akin T1 - Evaluation of the Stress and Displacement Behavior of Different LS-Dyna Element Types in Combination with Different Anti-Hourglassing Formulations and Initial Element Deformations T2 - Kurzfassungen der Vorträge, 13. LS-DYNA Forum 2014, 6. - 8. Oktober 2014, Bamberg Y1 - 2014 SN - 978-3-9816215-1-8 PB - DYNAmore GmbH CY - Stuttgart ER - TY - CHAP A1 - Kober, Markus A1 - Kühhorn, Arnold A1 - Stelldinger, Enrico A1 - Keskin, Akin T1 - Identification of Stiffness Parameters of a Simplified Aero-Engine Mount System by Using a Higher Fidelity Model of the Mount System T2 - Kurzfassungen der Vorträge, 13. LS-DYNA Forum 2014, 6. - 8. Oktober 2014, Bamberg Y1 - 2014 SN - 978-3-9816215-1-8 PB - DYNAmore GmbH CY - Stuttgart ER - TY - CHAP A1 - Kober, Markus A1 - Kühhorn, Arnold A1 - Keskin, Akin T1 - Implicit Time Integration Schemes for the FEM Simulation of Fast Rotating Structures T2 - WCCM XII & APCOM VI (World Congress on Computational Mechanics & Asia Pacific Congress on Computational Mechanics), Seoul, South Korea, 23.-29. Juli 2016 N2 - Due to the demand of more and more detailed FEM simulation results of whole aero-engine models, the number of DOF of such models (Fig. 1) increases dramatically. Although the available computational power for the solution of such highly nonlinear, dynamic boundary value problems also increased during the last years, the overall computational time of these high-fidelity models for the simulation of a few milliseconds of the running engine is in the order of several weeks even on high performance clusters with thousands of CPU cores. Typically, for such highly dynamic FEM computations explicit time integration schemes are used in order to solve the equations of motion. To keep such a numerical integration stable, the time step size may not exceed a certain critical time step size. Unfortunately, the critical time step size of an explicit time integration algorithm for the engine models under consideration is in the order of 10-8. This means that the simulation of a running engine over a time span of a few seconds results in a computational time of several years with clusters, which are available nowadays. Therefore, implicit time integration schemes, which are unconditionally stable and allow much bigger time steps, have to be used. Since in an implicit integration, in contrast to an explicit one, an equilibrium iteration is always necessary, the computational costs for an implicit time step are much higher than for an explicit time step. Almost all commercial FE codes use the classical Newmark implicit time integration scheme. It will be shown that this algorithm fails especially for the simulation of fast rotating structures if bigger time steps are used. This is demonstrated at the example of academic examples as well as for more realistic rotor models. To overcome the problems of the Newmark integration, a 3-Point-Newmark- Euler-Backward integration scheme [1,2] has been selected, which consists of alternating Newmark and 3-Point-Euler-Backward steps. The additional interpolation information for the Euler-step is provided by the previous Newmark step. This integration procedure has been implemented and successfully applied to the FEM simulation of fast rotating structures, which will be also demonstrated during the presentation. Y1 - 2016 UR - http://wccm2016.org/data/WCCM_Proceeding_v2.1.pdf UR - http://wccm2016.org/wp/pdf/150917.pdf 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 - 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 - 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 - Keskin, Akin A1 - Kober, Markus A1 - Stelldinger, Enrico A1 - Kühhorn, Arnold A1 - Böhm, Holger A1 - Hornig, Andreas A1 - Hufenbach, Werner T1 - On the quantification of errors of a pre-processing effort reducing contact meshing approach : AIAA 2015-0408 T2 - 53rd AIAA Aerospace Sciences Meeting 2015, Kissimmee, Florida, USA, 5 - 9 January 2015, held at the AIAA SciTech Forum 2015, vol. 4 Y1 - 2015 SN - 978-1-5108-0117-2 U6 - https://doi.org/10.2514/6.2015-0408 SP - 3113 EP - 3124 PB - Curran CY - Red Hook, NY 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 - JOUR A1 - Bestle, Dieter A1 - Keskin, Akin T1 - Verbesserter Designprozess für moderne Hochdruckverdichter Y1 - 2004 ER - TY - CHAP A1 - Keskin, Akin A1 - Swoboda, Marius A1 - Flassig, Peter Michael A1 - Dutta, Amit Kumar A1 - Bestle, Dieter T1 - New Optimization Strategy for Rapid industrial Blade Design Y1 - 2009 ER - TY - CHAP A1 - Keskin, Akin A1 - Dutta, Amit Kumar A1 - Bestle, Dieter T1 - Alternative Approach for Solving a Multi-Objective Optimization Problem in Aerodynamic Compressor Blade Design Y1 - 2006 ER - TY - CHAP A1 - Keskin, Akin A1 - Bestle, Dieter T1 - Application of Multi-objective Optimization to Axial Compressor Preliminary Design KW - axial compressor KW - aerodynamic design KW - meanline prediction KW - multi-objective optimization Y1 - 2005 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 - THES A1 - Keskin, Akin T1 - Process integration and automated multi-objective optimization supporting aerodynamic compressor design KW - Verdichter KW - Aerodynamik KW - Optimierung KW - Verdichterauslegung KW - Mehrkriterien-Optimierung KW - Prozessintegration Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:co1-opus-484 SN - 978-3-8322-5875-7 PB - Shaker CY - Achen ER - TY - JOUR A1 - Keskin, Akin A1 - Bestle, Dieter T1 - Application of Multi-objective Optimization to Axial Compressor Preliminary Design JF - Aerospace science and technology Y1 - 2006 SN - 0034-1223 SN - 1270-9638 VL - 10 IS - 7 SP - 581 EP - 589 ER - TY - GEN A1 - Swoboda, Marius A1 - Huppertz, André A1 - Keskin, Akin A1 - Otto, Dierk A1 - Bestle, Dieter T1 - Multidisciplinary Compressor Blading Design Process using Automation and Multi-Objective optimization Y1 - 2006 ER -