@misc{deSilvaKuehhornGolze, author = {de Silva, Tina and K{\"u}hhorn, Arnold and Golze, Mark}, title = {Homogenization of thin structured sheet metals by using FEM}, series = {Proceedings in applied mathematics and mechanics : PAMM}, volume = {12}, journal = {Proceedings in applied mathematics and mechanics : PAMM}, number = {1}, doi = {10.1002/pamm.201210104}, pages = {227 -- 228}, language = {en} } @misc{BeirowGolzePopig, author = {Beirow, Bernd and Golze, Mark and Popig, Frederik}, title = {Vibration Reduction of a Steam Turbine Wheel by Means of Intentional Mistuning}, series = {Advances in Mechanism Design III : Proceedings of TMM 2020}, journal = {Advances in Mechanism Design III : Proceedings of TMM 2020}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-83593-4}, issn = {2211-0984}, doi = {10.1007/978-3-030-83594-1_8}, pages = {73 -- 82}, abstract = {A last stage steam turbine wheel is analyzed with the objective to alleviate the flutter susceptibility by employing intentional mistuning (IM). In particular, the operation at nominal speed under part-load conditions may cause unfavorable flow conditions facilitating flow separation. In consequence, negative aerodynamic damping ratios occur for the first bending mode family in some circumstances. Employing intended alternate mistuning of adequate magnitude has proved to be a promising measure to stabilize rotors in terms of avoiding self-excited vibration phenomena. From the manufacturing point of view, this two-blade design is advantageous as well and hence, chosen here as a first measure to attenuate flutter susceptibility. Two prototypes of bladed disks series have been made, which are exhibiting small but unavoidable deviations from the design intention due to manufacturing. The real blade alone frequencies have been identified within foregoing experimental investigations. Numerical modal analyses carried out for the prototypes as manufactured finally reveal that there is an additional positive contribution of random mistuning in terms of further enhancing the least aerodynamic damping ratio. Another promising and robust IM pattern is found by using generic algorithms to optimize the least aerodynamic damping ratio yielding stable conditions at any time as well. Moreover, it shows that IM combined with random mistuning also mitigates the maximum forced response at part-speed conditions.}, language = {en} } @incollection{BeirowGolzePopig, author = {Beirow, Bernd and Golze, Mark and Popig, Frederik}, title = {Vibration Reduction of a Steam Turbine Wheel by Means of Intentional Mistuning}, series = {Advances in Mechanism Design III}, booktitle = {Advances in Mechanism Design III}, editor = {Beran, Jaroslav and B{\´i}lek, Martin and V{\´a}clav{\´i}k, Miroslav and Žabka, Petr}, publisher = {Springer International Publishing}, address = {Heidelberg}, isbn = {978-3-030-83593-4}, issn = {2211-0984}, doi = {10.1007/978-3-030-83594-1_8}, pages = {73 -- 82}, abstract = {A last stage steam turbine wheel is analyzed with the objective to alleviate the flutter susceptibility by employing intentional mistuning (IM). In particular, the operation at nominal speed under part-load conditions may cause unfavorable flow conditions facilitating flow separation. In consequence, negative aerodynamic damping ratios occur for the first bending mode family in some circumstances. Employing intended alternate mistuning of adequate magnitude has proved to be a promising measure to stabilize rotors in terms of avoiding self-excited vibration phenomena. From the manufacturing point of view, this two-blade design is advantageous as well and hence, chosen here as a first measure to attenuate flutter susceptibility. Two prototypes of bladed disks series have been made, which are exhibiting small but unavoidable deviations from the design intention due to manufacturing. The real blade alone frequencies have been identified within foregoing experimental investigations. Numerical modal analyses carried out for the prototypes as manufactured finally reveal that there is an additional positive contribution of random mistuning in terms of further enhancing the least aerodynamic damping ratio. Another promising and robust IM pattern is found by using generic algorithms to optimize the least aerodynamic damping ratio yielding stable conditions at any time as well. Moreover, it shows that IM combined with random mistuning also mitigates the maximum forced response at part-speed conditions.}, language = {en} } @misc{BeirowGolzePopig, author = {Beirow, Bernd and Golze, Mark and Popig, Frederik}, title = {Application of Intentional Mistuning to Reduce the Vibration Susceptibility of a Steam Turbine Wheel}, series = {ASME 2022 Turbomachinery Technical Conference \& Exposition (GT2022)}, journal = {ASME 2022 Turbomachinery Technical Conference \& Exposition (GT2022)}, abstract = {Intentional mistuning (IM) is employed on a last stage turbine wheel to alleviate both the flutter susceptibility and maximum forced response. Primarily, operations at nominal speed under part-load conditions may cause unfavorable flow conditions facilitating flow separation. As a consequence, the original design intention with identical blades features negative aerodynamic damping ratios with respect to the first bending mode family. In order to prevent any self-excited vibration phenomena, intentional alternate mistuning is utilized to increase the least aerodynamic damping ratio as far as it takes a positive value and hence, to contribute to a stabilization of the rotor. For the purpose of numerically analyzing the vibration behavior, reduced order models are built up, which are based on modal reduction techniques, namely the subset of nominal system modes (SNM) [1] and the fundamental mistuning model (FMM) [2]. These types of models conveniently allow for considering both, different mistuning distributions in terms of probabilistic analyses and the aeroelastic interaction by means of prescribing aerodynamic damping ratios and aeroelastic natural frequencies of the tuned counterpart or aerodynamic influence coefficients, respectively. A detailed study is presented regarding the correction of frequency mistuning magnitudes in terms of considering the impact of centrifugal stiffening, which plays a significant role in case of long low pressure turbine blades featuring high aspect ratios. Since alternate IM cannot be implemented perfectly, every bladed wheel as manufactured will exhibit small but unavoidable structural deviations from the design intention, which are known as random mistuning. To ensure the robustness of the IM solution in terms of positive aerodynamic damping ratios at any time, comprehensive probabilistic analyses are conducted with respect to superimposing random structural mistuning at first. Secondly, the impact of varying mistuning magnitude is analyzed. Thirdly, the robustness towards aerodynamic mistuning is investigated by means of small variations of aeroelastic influence coefficients and consequently, the inter blade phase angle dependent aerodynamic damping curves. Moreover, it becomes apparent that alternate IM superimposed with both, random structural and aerodynamic mistuning also mitigates the maximum forced response at part-speed conditions.}, language = {en} } @misc{BeirowNakosGolzeetal., author = {Beirow, Bernd and Nakos, Alex and Golze, Mark and Vogt, Damian and Wirsum, Manfred and Schafferus, Markus and Sasakaros, Marios}, title = {Forced response reduction of a turbine impeller}, series = {Advances in Mechanism Design IV, Proceedings of TMM 2024}, journal = {Advances in Mechanism Design IV, Proceedings of TMM 2024}, publisher = {Springer}, address = {Cham}, isbn = {978-3-031-70253-2}, issn = {2211-0984}, doi = {10.1007/978-3-031-70251-8_6}, pages = {53 -- 65}, language = {en} }