@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{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} }