TY - GEN A1 - Beirow, Bernd A1 - Maywald, Thomas A1 - Figaschewsky, Felix A1 - Kühhorn, Arnold A1 - Heinrich, Christoph Rocky A1 - Giersch, Thomas T1 - Simplified Determination of Aerodynamic Damping for Bladed Rotors, Part 1: Experimental Validation at Rest T2 - ASME Turbo Expo 2016, Turbomachinery Technical Conference and Exposition, Volume 7B, Structures and Dynamics, Seoul, South Korea, June 13–17, 2016 N2 - Considering both a radial turbine rotor of a turbocharger and an axial compressor test blisk at rest, aerodynamic damping characteristics are experimentally and numerically analyzed. Linear dependencies of modal damping ratios on the ambient pressure or the acoustic impedance, respectively, could be shown within experiments carried out inside a pressure chamber. The impact of the ambient air clearly dominates the modal damping ratios compared to the minor contribution of the structure. Assuming that acoustic emission can be regarded as main source of aerodynamic damping a simplified approach for its determination is introduced which only depends on natural frequency, mode shape and acoustic impedance. It is shown that a satisfying match between experiment and computation is achieved for those cases which are dedicated to sufficiently small ratios between wave lengths of acoustic emissions and blade distances. Y1 - 2016 SN - 978-0-7918-4984-2 U6 - https://doi.org/10.1115/GT2016-56535 N1 - Paper No. GT2016-56535 PB - ASME CY - New York, NY 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 - Part 2: Influence of Different Inlet Guide Vane Configurations T2 - Proceedings of ASME Turbo Expo 2023, Boston, Massachusetts, June 26-30, 2023, Volume 11, A. Aerodynamics excitation and damping, bearing and seal dynamics N2 - The occurrence of blade vibrations in radial turbines leads to limit cycle oscillations, which in time increase the risk of component failure due to high cycle fatigue. In this context, the precise determination of the resonance operating points and the estimation of the vibration magnitudes are essential for an accurate assessment of the service life of the turbocharger components. In radial turbines forced blade vibrations are primarily flow induced. These vibrations are produced by the non-uniform flow field in the circumferential direction which acts on the blades as a cyclic pressure fluctuation. Previous studies have identified the inlet guide vane (IGV) and the spiral turbine housing as the primary sources of the non-uniform flow field. In the present study a thorough experimental investigation of the synchronous blade vibrations of a radial turbine is performed. First, the blade vibration modes were measured experimentally and calculated numerically for the determination of the speed ranges that need to be examined. Subsequently, the vibrations were captured with two redundant measurement systems during real turbocharger operation. Strain gauges were applied on certain blades while eight optical sensors were distributed on the circumference of the turbine shroud for the measurement of the blades tips deflection through a commercial tip-timing system. In the first part, the blade vibrations caused by the “nominal” IGV are presented. Part 2 analyses the changes of the blade vibrations due to the application of two different IGVs. The first IGV has the same number of vanes as the “nominal” IGV. Nevertheless, it generates additional low engine order excitations by intentionally varying the distance between the vanes. Next, an IGV with a higher number of vanes is employed for the excitation at higher frequencies and thus of higher blade modes. Contrary to expectations, certain synchronous vibrations can be measured in the experiments of all IGVs. These cannot be attributed to the spiral turbine casing. KW - synchronous blade vibrations KW - flow induced vibrations KW - mistuning Y1 - 2023 SN - 978-0-7918-8705-9 U6 - https://doi.org/10.1115/GT2023-102243 N1 - Projekt Nr. BTU: 35057002 FVV/AiF-Projekt PB - ASME CY - New York ER -