@inproceedings{KoberKuehhornKeskinetal., author = {Kober, Markus and K{\"u}hhorn, Arnold and Keskin, Akin and Singh, Kai Navtej}, title = {Challenges and opportunities of thermomechanical FEM simulations of high fidelity aero-engine models by implicit time-integration}, series = {Proceedings of ISABE 2017, ISABE-2017-22568, Manchester, September 3.-8., 2017}, booktitle = {Proceedings of ISABE 2017, ISABE-2017-22568, Manchester, September 3.-8., 2017}, publisher = {ISABE}, pages = {10}, language = {en} } @inproceedings{FigaschewskyKuehhornBeirowetal., author = {Figaschewsky, Felix and K{\"u}hhorn, Arnold and Beirow, Bernd and Giersch, Thomas and Schrape, Sven}, title = {Analysis of Mistuned Forced Response in an Axial High Pressure Compressor Rig With Focus on Tyler-Sofrin Modes}, series = {ISABE 2017, ISABE-2017-22614, Manchester, September 3.-8., 2017}, booktitle = {ISABE 2017, ISABE-2017-22614, Manchester, September 3.-8., 2017}, publisher = {ISABE}, pages = {21}, language = {en} } @inproceedings{BeirowKuehhornFigaschewskyetal., author = {Beirow, Bernd and K{\"u}hhorn, Arnold and Figaschewsky, Felix and H{\"o}nisch, Peter and Giersch, Thomas and Schrape, Sven}, title = {Model Update and Validation of a Mistuned High Pressure Compressor Blisk}, series = {Proceedings of ISABE 2017, ISABE-2017-22568, Manchester, September 3.-8., 2017}, booktitle = {Proceedings of ISABE 2017, ISABE-2017-22568, Manchester, September 3.-8., 2017}, publisher = {ISABE}, pages = {14}, language = {en} } @inproceedings{FigaschewskyGierschKuehhorn, author = {Figaschewsky, Felix and Giersch, Thomas and K{\"u}hhorn, Arnold}, title = {Forced Response Prediction of an Axial Turbine Rotor With Regard to Aerodynamically Mistuned Excitation}, series = {ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Volume 7B: Structures and Dynamics, D{\"u}sseldorf, Germany, June 16-20, 2014, Paper GT2014-25896}, booktitle = {ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Volume 7B: Structures and Dynamics, D{\"u}sseldorf, Germany, June 16-20, 2014, Paper GT2014-25896}, publisher = {ASME}, isbn = {978-0-7918-4577-6}, doi = {10.1115/GT2014-25896}, pages = {13}, abstract = {The design of both efficient and reliable turbomachinery blades demands a detailed knowledge of static and dynamic forces during operation. This paper aims to contribute to the proper identification of dynamic excitation mechanisms acting on an axial turbine rotor, particularly with regard to deviations of the NGV's nominal geometry due to the use of variable vanes or tolerances in manufacturing. As variations of the NGV's geometry disturb the perfectly periodic pattern of the downstream flow features, other spectral components than those correlated with the number of stator vanes are possible to appear. These frequency components may lead to low engine order excitation of fundamental blade modes at high engine speeds. Under these operating conditions the rotor is already highly loaded with centrifugal forces and additional dynamic excitation may cause unacceptable stresses. Thus aerodynamic mistuning might be a limiting criterion for the design of a highly loaded turbine rotor. Within this paper 2 dimensional CFD-models are used to investigate both, the determination of the wake of a geometric mistuned stator guide vane and the influence of the resulting excitation on the adjacent rotor stage due to aerodynamically mistuned flow. In order to generate a mistuned NGV geometry, variations of pitch and stagger angle are taken into account and a mesh morpher is used to produce computational domains of the mistuned geometry on the basis of a nominal mesh. Additionally a simplified reconstruction process based on a set of CFD computations will be introduced, being able to reproduce the spectral components of the mistuned wake by specifying a certain geometric mistuning distribution. The prediction of the resulting modal forces is carried out in time domain and approaches with lower fidelity are investigated with respect to their capability of reproducing the key features of an aerodynamically mistuned excitation mechanism.}, language = {en} } @inproceedings{RauerKuehhornSpringmann, author = {Rauer, Georg and K{\"u}hhorn, Arnold and Springmann, Marcel}, title = {Residual Stress Modelling and Inverse Heat Transfer Coefficients Estimation of a Nickel-Based Superalloy Disc Forging}, series = {ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Volume 6, D{\"u}sseldorf, Germany, June 16-20, 2014, Paper GT2014-25827}, booktitle = {ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Volume 6, D{\"u}sseldorf, Germany, June 16-20, 2014, Paper GT2014-25827}, publisher = {ASME}, isbn = {978-0-7918-4575-2}, doi = {10.1115/GT2014-25827}, abstract = {Aero engine disc forgings are subjected to heat treatment operations, i.e., solution treatment followed by quenching and artificial aging, with the aim of achieving improved mechanical material properties. During heat treatment high inhomogeneous temperature gradients and long loading times at elevated temperatures occur and lead to the development and partial relaxation of bulk residual stresses. The intention of this paper is to describe the residual stress modelling of a nickel-based ATI 718Plus® superalloy disc forging. For this purpose, an uncoupled thermomechanical finite element problem is solved consisting of a thermal model based on transient, spatially varying heat transfer coefficients (HTCs) and a stress model incorporating the nonlinear material behaviour to account for thermal induced inelastic deformations. A graphical user interface based application has been created for the automatic estimation of the a priori unknown HTCs by using a serial solution procedure for the two dimensional inverse heat conduction problem (IHCP) based on the function specification method. The estimated temperature fields have been compared at the thermocouple positions with the corresponding measurement data and confirm the suitability of the inverse algorithm to this problem. A rate-independent elasto-plastic constitutive model is used to simulate the residual stress formation while quenching the disc forging. Two creep models have been adjusted to uniaxial tensile test data and applied to simulate the stress relaxation during aging. Finally, this paper presents the numerical results of the stress analysis. Copyright © 2014 by Rolls-Royce Deutschland Ltd \& Co KG}, language = {en} } @inproceedings{BeirowKuehhornGierschetal., author = {Beirow, Bernd and K{\"u}hhorn, Arnold and Giersch, Thomas and Nipkau, Jens}, title = {Optimization-Aided Forced Response Analysis of a Mistuned Compressor Blisk}, series = {ASME Turbo Expo 2014, Turbine Technical Conference and Exposition, Volume 7B: Structures and Dynamics, D{\"u}sseldorf, Germany, June 16-20, 2014, Paper GT2014-25915}, booktitle = {ASME Turbo Expo 2014, Turbine Technical Conference and Exposition, Volume 7B: Structures and Dynamics, D{\"u}sseldorf, Germany, June 16-20, 2014, Paper GT2014-25915}, publisher = {ASME}, isbn = {978-0-7918-4577-6}, doi = {10.1115/GT2014-25915}, pages = {11}, abstract = {The forced response of the first rotor of an E3E-type high pressure compressor blisk is analyzed with regard to varying mistuning, varying engine order excitations and the consideration of aeroelastic effects. For that purpose, SNM-based reduced order models are used in which the disk remains unchanged while the Young's modulus of each blade is used to define experimentally adjusted as well as intentional mistuning patterns. The aerodynamic influence coefficient technique is employed to model aeroelastic interactions. Furthermore, based on optimization analyses and depending on the exciting EO and aerodynamic influences it is searched for the worst as well as the best mistuning distributions with respect to the maximum blade displacement. Genetic algorithms using blade stiffness variations as vector of design variables and the maximum blade displacement as objective function are applied. An allowed limit of the blades' Young's modulus standard deviation is formulated as secondary condition. In particular, the question is addressed if and how far the aeroelastic impact, mainly causing aerodynamic damping, combined with mistuning can even yield a reduction of the forced response compared to the ideally tuned blisk. It is shown that the strong dependence of the aerodynamic damping on the inter-blade phase angle is the main driver for a possible response attenuation considering the fundamental blade mode. The results of the optimization analyses are compared to the forced response due to real, experimentally determined frequency mistuning as well as intentional mistuning. Copyright © 2014 by Rolls-Royce Deutschland Ltd \& Co KG}, language = {en} } @inproceedings{GierschFigaschewskyHoenischetal., author = {Giersch, Thomas and Figaschewsky, Felix and H{\"o}nisch, Peter and K{\"u}hhorn, Arnold and Schrape, Sven}, title = {Numerical Analysis and Validation of the Rotor Blade Vibration Response Induced by High Pressure Compressor Deep Surge}, series = {ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Volume 7B: Structures and Dynamics D{\"u}sseldorf, Germany, June 16-20, 2014, Paper GT2014-26295}, booktitle = {ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Volume 7B: Structures and Dynamics D{\"u}sseldorf, Germany, June 16-20, 2014, Paper GT2014-26295}, publisher = {ASME}, address = {New York, NY}, isbn = {978-0-7918-4577-6}, doi = {10.1115/GT2014-26295}, pages = {12}, abstract = {The following paper presents a numerical analysis of a deep surge cycle of a 4.5 stage research compressor. The resulting unsteady loads are used to determine the response of two particular rotor blade rows that are then compared to strain gauge data from measurements. Within a deep surge cycle the compressor experiences a rapid change of the flow field from forward to reversed flow. This rapid breakdown is linked to a new mean blade load. Hence, the rapid change in blade loads are able to excite fundamental blade modes similar to an impulse load. The resulting vibration magnitudes might reach critical levels. This paper demonstrates two different approaches to evaluate the unsteady flow during a surge cycle. The first uses a three dimensional, time accurate finite volume solver for viscid compressible flows to calculate the transient surge cycle of the compressor. The compressor itself is represented by a multi-blade-row sector model. The second approach makes use of the same solver and compressor domain to determine steady state characteristics of the HPC in forward, stalled and reversed flow. Based on these characteristics an one dimensional finite volume solver for inviscid compressible flows was developed to determine the transient compressor behavior. The one dimensional solver represents the compressor by source terms that are linked to the previously determined steady state characteristics. Copyright © 2014 by Rolls-Royce Deutschland Ltd \& Co KG}, language = {en} } @inproceedings{ReyVillazonWildowKuehhornetal., author = {Rey Villaz{\´o}n, Jos{\´e} Maria and Wildow, Toni and K{\"u}hhorn, Arnold and Benton, Robert and G{\"o}hler, Moritz}, title = {Impact of the Secondary Air System Design Parameters on the Calculation of Turbine Discs Windage}, series = {ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Volume 5C: Heat Transfer, D{\"u}sseldorf, Germany, June 16-20, 2014, Paper GT2014-26050}, booktitle = {ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Volume 5C: Heat Transfer, D{\"u}sseldorf, Germany, June 16-20, 2014, Paper GT2014-26050}, publisher = {ASME}, address = {New York, NY}, isbn = {978-0-7918-4573-8}, doi = {10.1115/GT2014-26050}, pages = {9}, abstract = {The rotating components in gas turbines are very highly stressed as a result of the centrifugal and thermal loads. One of the main functions of the secondary air system (SAS) is to ensure that the rotating components are surrounded by air that optimizes disc lifing and integrity. The SAS is also responsible for the blade cooling flow supply, preventing hot gas ingestion from the main annulus into the rotor-stator cavities, and for balancing the net axial load in the thrust bearings. Thus, the SAS design requires a multidisciplinary compromise to provide the above functions, while minimizing the penalty of the secondary flows on engine performance. The phenomenon known as rotor-stator drag or windage is defined as the power of the rotor moment acting on its environment. The power loss due to windage has a direct impact on the performance of the turbine and the overall efficiency of the engine. This paper describes a novel preliminary design approach to calculate the windage of the rotor-stator cavities in the front of a typical aero engine HP turbine. The new method is applied to investigate the impact of the SAS design parameters on the windage losses and on the properties of the cooling flows leading to the main annulus. Initially, a theoretical approach is followed to calculate the power losses of each part of the HPT front air feed system. Then, a 1D-network integral model of the cavities and flow passages of the HPT front is built and enhanced with detailed flow field correlations. The new 1D-flow network model offers higher fidelity regarding local effects. A result comparison between the theoretical calculation and the prediction of the enhanced flow network model puts forward the relevance of the local flow field effects in the design concept of the SAS. Using the enhanced 1D-flow network models, the SAS design parameters are varied to assess their influence on the windage and pumping power calculation. As a conclusion, the paper shows how the SAS design can have a significant influence on the HPT overall power and the air that is fed back into the turbine blade rows. Controlling these features is essential to bid a competitive technology in the aero engine industry. Copyright © 2014 by Rolls-Royce Deutschland Ltd \& Co KG}, language = {en} } @inproceedings{BeirowMaywaldKuehhorn, author = {Beirow, Bernd and Maywald, Thomas and K{\"u}hhorn, Arnold}, title = {Mistuning and Damping Analysis of a Radial Turbine Blisk in Varying Ambient Conditions}, series = {ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Volume 7B: Structures and Dynamics D{\"u}sseldorf, Germany, June 16-20, 2014, Paper GT2014-25521}, booktitle = {ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Volume 7B: Structures and Dynamics D{\"u}sseldorf, Germany, June 16-20, 2014, Paper GT2014-25521}, publisher = {ASME}, isbn = {978-0-7918-4577-6}, doi = {10.1115/GT2014-25521}, abstract = {A mistuned radial turbine impeller is analyzed with respect to the impact of varying ambient pressures and temperatures as well on frequency response functions and modal damping ratios. Beginning at room conditions, a finite element model of an impeller wheel at rest is updated based on experimentally determined mistuning in terms of blade dominated frequencies. The following numerical forced response analyses yield a maximum blade displacement amplification of 67\% compared to the tuned reference. In addition, modal damping ratios are determined in dependence on the ambient pressure ranging from technical vacuum at 1 mbar up to 6000 mbar in a pressure chamber. Shaker excitation and laser Doppler vibrometry response measurement is employed in this context. A linear dependence of modal damping ratios on ambient pressure and a dominating damping contribution of the surrounding air even for higher modes could be proved. Moreover, the experimental determination of frequency response functions (FRF) at technical vacuum yields a better separation of resonance peaks compared to room conditions at 1013 mbar and hence, this data allows for more accurate model-updates in principle. It is proved that numerical models updated regarding mistuning at room conditions are well suited to predict the forced response at arbitrary pressures if measured modal damping ratios at these pressures are considered. Finally, within analyzing the effect of increasing structural temperatures with the surrounding air at 1013 mbar included slightly decreasing resonance frequencies but strongly increasing FRF-amplitudes are determined. Copyright © 2014 by ASME}, language = {en} } @inproceedings{BehnamKuehhorn, author = {Behnam, Nouri and K{\"u}hhorn, Arnold}, title = {Automated CAE process for thermo-mechanical lifing prediction of a parameterized turbine blade with internal cooling}, series = {Joined 11th World Congress on Computational Mechanics (WCCM XI), 5th European Conference on Computational Mechanics (ECCM V), 6th European Conference on Computational Fluid Dynamics (ECFD VI) conference}, booktitle = {Joined 11th World Congress on Computational Mechanics (WCCM XI), 5th European Conference on Computational Mechanics (ECCM V), 6th European Conference on Computational Fluid Dynamics (ECFD VI) conference}, language = {en} }