Session: 22-03 Advanced Aeroelastic Prediction and Validation

Paper Number: 124275

124275 - Aeroelastic Influence of Blade-Shaft Coupling in a 1 1/2-Stage Axial Compressor 

During the design process of turbomachinery, it is often not possible to realize aerodynamically optimal designs due to aeroelastic constraints. The design choices are limited by possible structural failure, which can be caused by high vibration amplitudes, e.g. due to self-excited vibrations (flutter) or forced vibrations (forced response). In particular, the modal damping has an important impact on these phenomena. In the absence of frictional contacts, damping is mainly created by aerodynamics. In this work, the influence of additional damping due to the rotor bearing on the total damping and on the vibrational behaviour at forced response will be investigated. This influence becomes relevant when blade vibrations in nodal diameters 1 and -1 couple with the shaft vibrations. This is caused by a structural dynamic interaction of these two components. For the investigations, a simulation process is set up to best represent the physical effects during operation. The simulation process is essentially based on a full structural dynamic model of the blisk-shaft assembly and an unsteady CFD model using the harmonic balance method to account for the aeroelastic effects. In addition, a mistuning identification of the blading is performed based on an experimental modal analysis at standstill. All results are incorporated into a structural dynamic reduced-order model that calculates the vibrational behavior of the blading. The numerical results are compared with measurement data. In particular, this includes damping determined in operation using an acoustic excitation system and measured frequency responses due to forced response. The numerical results show very good agreement with the experimental results within the measurement uncertainty, both with respect to the damping and the mistuned frequency responses. Furthermore, the blade-shaft coupling results in significant changes of the eigenfrequencies and damping. As a consequence, damping increases by up to fifteen times when taking the coupling into account. This leads to an amplitude reduction by a factor of nine for the mistuned blade responses. Consequently, higher structural safety factors can be achieved in the design process by taking the blade-shaft coupling into account, so that potentials in the aerodynamic design can be better exploited.

Presenting Author: Niklas Maroldt Institute of Turbomachinery and Fluid Dynamics - Leibniz University Hannover

Presenting Author Biography: Niklas Maroldt studied industrial engineering at Leibniz University Hannover in Germany. He earned his master’s degree in 2018. Since 2019 he has worked as a research assistant at the Institute of Turbomachinery and Fluid Dynamics of the Leibniz University Hannover. His main research area is the aeroelasticity of axial compressors, in particular under the consideration of aeroacoustics and multistage effects.

Authors:

Niklas Maroldt Institute of Turbomachinery and Fluid Dynamics - Leibniz University Hannover
Joerg R. Seume Institute of Turbomachinery and Fluid Dynamics - Leibniz University Hannover