@misc{BeirowKuehhornFigaschewskyetal., author = {Beirow, Bernd and K{\"u}hhorn, Arnold and Figaschewsky, Felix and Bornholm, Alfons and Repetckii, Oleg V.}, title = {Forced Response Reduction of a Blisk by Means of Intentional Mistuning}, series = {Journal of Engineering for Gas Turbines and Power}, volume = {141}, journal = {Journal of Engineering for Gas Turbines and Power}, number = {1}, issn = {1528-8919}, doi = {10.1115/1.4040715}, pages = {011008-1 -- 011008-8}, abstract = {The effect of intentional mistuning has been analyzed for an axial turbocharger blisk with the objective of limiting the forced response due to low engine order excitation (LEO). The idea behind the approach was to increase the aerodynamic damping for the most critical fundamental mode in a way that a safe operation is ensured without severely losing aerodynamic performance. Apart from alternate mistuning a more effective mistuning pattern is investigated, which has been derived by means of optimization employing genetic algorithms. In order to keep the manufacturing effort as small as possible only two blade different geometries have been allowed which means that an integer optimization problem has been formulated. Two blisk prototypes have been manufactured for the purpose of demonstrating the benefit of the intentional mistuning pattern identified in this way: A first one with and a second one without employing intentional mistuning. The real mistuning of the prototypes has been experimentally identified. It is shown that the benefit regarding the forced response reduction is retained in spite of the negative impact of unavoidable additional mistuning due to the manufacturing process. Independently, further analyzes have been focused on the robustness of the solution by considering increasing random structural mistuning and aerodynamic mistuning as well. The latter one has been modeled by means of varying aerodynamic influence coefficients (AIC) as part of Monte Carlo simulations. Reduced order models have been employed for these purposes.}, language = {en} } @misc{RepetckiiVinhBeirow, author = {Repetckii, Oleg V. and Vinh, Nguyen Van and Beirow, Bernd}, title = {Sensitivity Analysis Regarding the Impact of Intentional Mistuning on Blisk Vibrations}, series = {Mechanisms and Machine Science}, volume = {125}, journal = {Mechanisms and Machine Science}, publisher = {Springer}, address = {Cham}, issn = {2211-0992}, doi = {10.1007/978-3-031-15758-5_41}, pages = {408 -- 415}, abstract = {The effect of different intentional mistuning (IM) patterns is investigated with respect to the forced response of an academic axial blisk. It could be shown in numerical analyses that a preliminary use of sensitivity algorithms helps to understand the feasibility and efficiency of introducing geometric changes of the blades. The implementation of IM patterns requires conducting intensive sensitivity studies based on FE simulations in order to identify the consequences of slight geometrical blade modifications on natural frequencies. Typical changes might be a modification of fillet radii or partial modifications of blade thickness, which are most suitable to adjust a target natural frequency without a severe loss of aerodynamic performance. A software tool developed at Irkutsk SAU is employed to evaluate the impact of mass and stiffness contributions, and with that, geometric deviations on blade natural frequencies. Intensive blade vibration due to aerodynamic excitation of blisks is known as major source of high cycle fatigue, which may cause severe failures of turbine and compressor wheels during operation. The problem is relevant for several sectors of industry such as power generation, aviation or vehicle manufacturing. In consequence, there is a broad request of preventing any inadmissible vibration at any time. The application of IM can be regarded as powerful tool to avoid both, large forced responses and self-excited vibration. However, there is a lack of knowledge about how to implement mistuning without strong distortions of the flow passage. The main objective of this work is to close this gap based on comprehensive numerical analyses with regard to the effects of intended geometric modifications of blades on modal quantities. Using FE models, the effectiveness of the proposed block models of mistuning is analyzed with and without taking into account the operational speed of the axial impeller. In conclusion, the consequences of different IM implementations on the forced response of an academic blisk are discussed. In particular, the most promising IM patterns are identified yielding the least forced response.}, language = {en} } @inproceedings{BeirowKuehhornFigaschewskyetal., author = {Beirow, Bernd and K{\"u}hhorn, Arnold and Figaschewsky, Felix and Bornholm, Alfons and Repetckii, Oleg V.}, title = {Forced Response Reduction of a Blisk by Means of Intentional Mistuning}, series = {ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition, Volume 7C: Structures and Dynamics, Oslo, Norway, June 11-15, 2018}, booktitle = {ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition, Volume 7C: Structures and Dynamics, Oslo, Norway, June 11-15, 2018}, publisher = {ASME}, address = {New York, NY}, isbn = {978-0-7918-5115-9}, doi = {10.1115/GT2018-76584}, pages = {10}, abstract = {The effect of intentional mistuning has been analyzed for an axial turbocharger blisk with the objective of limiting the forced response due to low engine order excitation (LEO). The idea behind the approach was to increase the aerodynamic damping for the most critical fundamental mode in a way that a safe operation is ensured without severely losing aerodynamic performance. Apart from alternate mistuning a more effective mistuning pattern is investigated, which has been derived by means of optimization employing genetic algorithms. In order to keep the manufacturing effort as small as possible only two blade different geometries have been allowed which means that an integer optimization problem has been formulated. Two blisk prototypes have been manufactured for the purpose of demonstrating the benefit of the intentional mistuning pattern identified in this way: A first one with and a second one without employing intentional mistuning. The real mistuning of the prototypes has been experimentally identified. It is shown that the benefit regarding the forced response reduction is retained in spite of the negative impact of unavoidable additional mistuning due to the manufacturing process. Independently, further analyzes have been focused on the robustness of the solution by considering increasing random structural mistuning and aerodynamic mistuning as well. The latter one has been modeled by means of varying aerodynamic influence coefficients (AIC) as part of Monte Carlo simulations. Reduced order models have been employed for these purposes.}, language = {en} }