TY - CHAP A1 - Popig, Frederik A1 - Hönisch, Peter A1 - Kühhorn, Arnold T1 - Experimental and Numerical Analysis of Geometrical Induced Mistuning T2 - ASME Turbo Expo 2015: Turbine Technical Conference and Exposition Volume 7B: Structures and Dynamics Montreal, Quebec, Canada, June 15–19, 2015 N2 - The application of high pressure compressor (HPC) rotors manufactured as blisk (Blade Integrated Disk) is ever-expanding in modern jet engine designs. Despite the major advantages of less mass and higher efficiency, the most challenging problem is lower mechanical damping due to the loss of damping between blades root’s and the disk. Mistuning is induced by material inhomogeneities, manufacturing tolerances or wear during use and leads to amplitude magnification and mode localization. From the experimental point of view mistuning can be evaluated via experimental vibration analysis in terms of frequency deviations. Furthermore optical measurements can be evaluated in terms of geometrical deviations between the real and designed geometry. From the structural point of view a mistuned blisk model can be obtained by morphing the nodes of the geometrical tuned FE model or by performing blade individual stiffness mistuning due to modification of Young’s modulus. The following work is focused on the numerical prediction of mistuned blisk vibrations. Therefore, the research blisk of the 4 stage research compressor, manufactured as job-production, is analyzed. For this research blisk optical measurement data as well as experimentally obtained frequency patterns are available. In a first part mistuning identification in terms of experimental vibration analysis and Proper Orthogonal Decomposition of the geometrical deviations is presented. In a second part mistuning modeling in terms of stiffness mistuning and geometrical mistuning is applied to the tuned FE-model and the numerical results are evaluated against experimental data regarding accuracy. Furthermore, the impact of geometrical deviations on mistuning is analyzed. Copyright © 2015 by Rolls-Royce Deutschland Ltd & Co KG KW - Numerical analysis KW - Blades KW - Finite element model KW - Disks KW - Stiffness KW - Damping Y1 - 2015 UR - http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleID=2428632 SN - 978-0-7918-5677-2 U6 - https://doi.org/10.1115/GT2015-43272 PB - ASME CY - New York, NY 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 -