TY - GEN A1 - Nakos, Alex A1 - Beirow, Bernd A1 - Zobel, Arthur T1 - Vibration Analyses of Radial Turbine Wheels Considering Structural and Aerodynamic Mistuning T2 - Proceedings of Global Power and Propulsion Society N2 - Radial turbine wheels of exhaust gas turbochargers are permanently exposed to centrifugal, thermal, and aerodynamic loading. However, since these wheels are commonly designed as integral structures featuring relatively little mechanical damping, they are prone to the impact of unavoidable structural random mistuning, which may evoke severe magnifications of the forced response. Nonetheless, the safe operation of turbochargers has to be ensured at any time so that the contribution of aerodynamic damping is of particular importance. Moreover, the application of intentional mistuning is known to be a suitable measure to limit or even reduce the forced response by means of increasing the resulting aerodynamic damping. In this paper, two turbine wheels of the same type are considered, one manufactured with and another one without intentional mistuning. Experimental determinations of the mistuning patterns actually reveal deviations from the design intentions, which are considered in updated numerical models. Forced response simulations demonstrate that the targeted response reduction affected by intentional mistuning is achieved anyhow. Furthermore, the general robustness of the solution is proved with respect to the maximum forced response by means of comprehensive probabilistic numerical analyses addressing the impact of additional random structural mistuning, the magnitude of intentional mistuning, and aerodynamic mistuning. Y1 - 2022 UR - https://gpps.global/gpps-chania22-proceedings/ U6 - https://doi.org/10.33737/gpps22-tc-61 SN - 2504-4400 ER - TY - GEN A1 - Kober, Markus A1 - Beirow, Bernd A1 - Singh, Kai Navtej T1 - Towards the Isogeometric Aero-Engine T2 - Proceedings of 16th German LS-DYNA Forum, 11.-12. Oktober 2022, Bamberg Y1 - 2022 UR - https://www.dynamore.it/en/training/conferences/upcoming/16th-german-ls-dyna-forum-2022/preliminary-agenda#tag-1 SN - 978-3-9816215-8-7 ER - TY - GEN A1 - Nakos, Alex A1 - Beirow, Bernd A1 - Wirsum, Manfred A1 - Schafferus, Markus A1 - Sasakaros, Marios A1 - Vogt, Damian A1 - Zobel, Arthur T1 - Mistuning and Damping of a Radial Turbine Wheel. Part 3: Validation of Intentional Mistuning During Machine Operation T2 - Proceedings of ASME Turbo Expo 2023, Boston, Massachusetts, June 26-30, 2023 N2 - This contribution investigates the implementation and verification of intentional mistuning (IM) to a radial turbine wheel of an exhaust turbocharger. In principle, inaccuracies in manufacture or material inhomogeneities may lead to random blade mistuning and thus localized modes with severely magnified blade vibrations can occur. With regard to axial compressors and turbines, IM has proved to be an efficient measure to mitigate the forced response. For radial turbine wheels, on the other hand, a successful implementation of IM into a wheel hardware has not yet been presented. This work aims at the design, implementation, and verification of successful IM considering both measurements at standstill and test runs on a turbocharger test rig. The fundamental analyses have been carried out in part one [1] of this three-part paper in order to find a suitable IM-pattern featuring only two different blade designs. The AABB sequence was identified to be the most promising one in terms of mitigating the maximum forced response of the fundamental bending mode at the considered operating point. In concrete terms, a 40% attenuation of the maximum forced response was predicted by employing reduced order models. The second part [2] discussed the detailed geometric adaption of the turbine wheel hardware focussing on the implementation and validation of the IM pattern under laboratory conditions (standstill). Part three is about validating the efficacy of IM under operating conditions. In that sense, the successful implementation of IM and thus the machining of the wheel hardware are investigated within the framework of test runs on a turbocharger test rig. Test runs are conducted for both a wheel with and a wheel without IM. Non-intrusive blade-tip-timing (BTT) technology is employed to record forced response data. A well-known approach to evaluate the raw data namely times of arrival (TOA) without the availability of a once-per-revolution (OPR) signal is adapted, implemented, and applied for the evaluation. The results are compared to those received by using a commercial evaluation software for BTT measurement data. Finally, the actual gain achieved by means of IM is discussed in detail. KW - Intentional Mistuning KW - Blade Vibration KW - Damping Y1 - 2023 SN - 978-0-7918-8706-6 U6 - https://doi.org/10.1115/GT2023-101993 ER - TY - GEN A1 - Gambitta, Marco A1 - Beirow, Bernd A1 - Klauke, Thomas T1 - Investigation of Rear Blisk Drum Dynamics Under Consideration of Multi-Stage Coupling T2 - Proceedings of ASME Turbo Expo 2023, Boston, Massachusetts, June 26-30, 2023 N2 - The analysis of the structural dynamics of multistage cyclic structures as linked components is required to model the interstage coupling. In turbomachinery, this can result in a collaboration between different compressor or turbine stages. This paper investigates the coupling between two rear drum blade integrated disk stages of an axial compressor to support the mechanical design process. Considering the vibration modeshapes of a multistage system, different components may co-participate in the dynamics. For this reason, a criteria to identify the modes affected by the coupling and to quantify this coupling is defined. This allows to distinguish between modes with inter-stage coupling, requiring the multistage system for their description, and uncoupled modes, involving a single stage. In addition, it is of interest to research methods to reduce the impact of the coupling on the vibrating system without drastically altering the geometry of the components. The vibration analyses of a two-stage compressor generalized geometry, representative of a compressor rear drum blisk, is presented as a study case. The use of a reducing method allows to describe the behavior of the nominal multistage system with a computationally efficient technique, enabling a parametric analysis of the stages’ coupling. The investigation considers the effect of a set of geometrical and mechanical parameters on the dynamics, identifying the driving parameters of the coupled vibration characteristics. Y1 - 2023 SN - 978-0-7918-8705-9 U6 - https://doi.org/10.1115/GT2023-103756 ER - TY - GEN A1 - Nakos, Alex A1 - Beirow, Bernd T1 - On the Influence of Installation on the Forced Response of Radial Turbine Wheels T2 - Proceedings of Global Power and Propulsion Society, GPPS Hongkong, October 16 - 19, 2023 N2 - Radial turbine wheels are commonly designed as integrally bladed rotors featuring extremely low structural damping in comparison to separate designs of blades and disk. Consequently, they are more prone to vibration. Moreover, random blade mistuning due to unavoidable inaccuracies in manufacture or material inhomogeneities can severely increase the maximum forced blade vibration amplitude compared to the tuned counterpart. Unfortunately, this response magnification may worsen in case of small damping. Since modes exhibiting blade dominated vibration are usually considered vulnerable in this regard, the influence of disk and shaft and its mounting conditions seems to be negligible. In this paper, reduced order models are employed in order to simulate the forced response of a radial turbine wheel. Experimental modal analyses have been carried out to provide realistic damping ratios considering both the single turbine wheel hardware as well as the full rotor mounted in a turbocharger test rig. Test runs are conducted and non-intrusive blade-tip-timing technology provides measurement data to validate the simulation models. Contrary to the original presumption, it is shown that additional structural damping contributed by assembling can significantly influence the forced response even though the focus is on blade dominated vibration. Y1 - 2023 U6 - https://doi.org/10.33737/gpps23-tc-138 SN - 2504-4400 ER - TY - GEN A1 - Gambitta, Marco A1 - Beirow, Bernd A1 - Schrape, Sven T1 - Modelling Method for Aeroelastic Low Engine Order Excitation Originating from Upstream Vanes’ Geometrical Variability T2 - International Journal of Turbomachinery Propulsion and Power N2 - The manufacturing geometrical variability in axial compressors is a stochastic source of uncertainty, implying that the real geometry differs from the nominal design. This causes the real geometry to lose the ideal axial symmetry. Considering the aerofoils of a stator vane, the geometrical variability affects the flow traversing it. This impacts the downstream rotor, especially when considering the aeroelastic excitation forces. Optical surface scans coupled with a parametrisation method allow for acquiring the information relative to the real aerofoils geometries. The measured data are included in a multi-passage and multi-stage CFD setup to represent the mistuned flow. In particular, low excitation harmonics on the rotor vane are introduced due to the geometrical deviations of the upstream stator. The introduced low engine orders, as well as their amplitude, depend on the stator geometries and their order. A method is proposed to represent the phenomena in a reduced CFD domain, limiting the size and number of solutions required to probabilistically describe the rotor excitation forces. The resulting rotor excitation forces are reconstructed as a superposition of disturbances due to individual stator aerofoils geometries. This indicates that the problem is linear in the combination of disturbances from single passages. KW - Aeroelasticity KW - Low Engine Order KW - Geometrical Variability Y1 - 2024 U6 - https://doi.org/10.3390/ijtpp9020012 SN - 2504-186X N1 - BTU-interne Projekt-Nr. 35059006 VL - 9 IS - 2 ER - TY - GEN A1 - Gambitta, Marco A1 - Beirow, Bernd A1 - Schrape, Sven T1 - Modelling method for aeroelastic low engine order excitation originating from upstream Vanes’ geometrical variability T2 - International Journal of Turbomachinery Propulsion and Power N2 - The manufacturing geometrical variability in axial compressors is a stochastic source of uncertainty, implying that the real geometry differs from the nominal design. This causes the real geometry to lose the ideal axial symmetry. Considering the aerofoils of a stator vane, the geometrical variability affects the flow traversing it. This impacts the downstream rotor, especially when considering the aeroelastic excitation forces. Optical surface scans coupled with a parametrisation method allow for acquiring the information relative to the real aerofoils geometries. The measured data are included in a multi-passage and multi-stage CFD setup to represent the mistuned flow. In particular, low excitation harmonics on the rotor vane are introduced due to the geometrical deviations of the upstream stator. The introduced low engine orders, as well as their amplitude, depend on the stator geometries and their order. A method is proposed to represent the phenomena in a reduced CFD domain, limiting the size and number of solutions required to probabilistically describe the rotor excitation forces. The resulting rotor excitation forces are reconstructed as a superposition of disturbances due to individual stator aerofoils geometries. This indicates that the problem is linear in the combination of disturbances from single passages. KW - Aeroelasticity KW - Low Engine Order KW - Geometrical Variability Y1 - 2024 SN - 2504-186X VL - 2024 ER - TY - GEN A1 - Sasakaros, Marios A1 - Schafferus, Markus A1 - Wirsum, Manfred A1 - Zobel, Arthur A1 - Vogt, Damian A1 - Nakos, Alex A1 - Beirow, Bernd T1 - Experimental Investigation of Synchronous-Flow-Induced Blade Vibrations on a Radial Turbine T2 - International Journal of Turbomachinery, Propulsion and Power N2 - In this study, a thorough experimental investigation of the synchronous blade vibrations of a radial turbine is performed for different IGV configurations. First, the blade modes are measured experimentally and calculated numerically. Subsequently, the vibrations are recorded with two redundant measurement systems during real operation. Strain gauges were applied on certain blades, while a commercial blade-tip-timing system is used for the measurement of blade deflections. The experimentally determined vibration properties are compared with numerical estimations. Initially, the vibrations recorded with the “nominal” IGV were presented. This IGV primarily generates nodal diameter (ND) 0 vibrations. Subsequently, the impact of two different IGV configurations is examined. First, a mistuned IGV, which has the same number of vanes as the “nominal” IGV is examined. By intentionally varying the distance between the vanes, additional low engine order excitations are generated. Moreover, an IGV with a higher number of vanes is employed to induce excitations at higher frequency modes and ND6 vibrations. Certain vibrations are consistently measured across all IGV configurations, which cannot be attributed to the spiral turbine casing. In addition, a turbine–compressor interaction has been observed. Y1 - 2024 U6 - https://doi.org/10.3390/ijtpp9040035 SN - 2504-186X VL - 9 IS - 4 PB - MDPI AG ER - TY - GEN A1 - Gambitta, Marco A1 - Beirow, Bernd A1 - Klauke, Thomas T1 - Structural dynamics of an axial compressor’s rear blisk drum and multi-stage coupling T2 - ASME Turbo Expo 2024: Turbomachinery Technical Conference and Exposition, June 24–28, 2024, London, United Kingdom Y1 - 2024 SN - 978-0-7918-8803-2 U6 - https://doi.org/10.1115/GT2024-128647 ER - TY - GEN A1 - Beirow, Bernd A1 - Nakos, Alex A1 - Golze, Mark A1 - Vogt, Damian A1 - Wirsum, Manfred A1 - Schafferus, Markus A1 - Sasakaros, Marios T1 - Forced response reduction of a turbine impeller T2 - Advances in Mechanism Design IV, Proceedings of TMM 2024 Y1 - 2024 SN - 978-3-031-70253-2 SN - 978-3-031-70250-1 U6 - https://doi.org/10.1007/978-3-031-70251-8_6 SN - 2211-0984 SP - 53 EP - 65 PB - Springer CY - Cham ER -