Session: 28 - 06: Experimental Techniques and Validation in Turbomachinery

Submission Number: 174971

Quantifying Impact Excitation Workflow Repeatability Through Modal Parameter Estimation Variability on Radial Turbine Blades 

Mistuning is an unavoidable effect in turbomachinery and bladed disk structures that affects their vibrational characteristics. The responses of such structures are highly sensitive to small changes of their parameters. Moreover, excitation and response measurements are needed in multiple areas around the structure to assess their integrity, making this experimental process time-consuming and subjective to possible measurement errors. The current research aims to show how variations in a nominal experimental workflow affect the variability of identified modal parameters. The structure under test is a turbocharger radial turbine subjected to impact excitations. The number of samples used in frequency domain averaging to produce repeatable frequency response functions (FRFs) and natural frequencies is initially studied. Next, the variability in the FRFs due to the impact force level is examined to additionally assess existence of non-linearities in the structure. The same experimental procedures are also implemented in different time periods to investigate how randomness in environmental factors affects modal parameter estimation. Finally, the effect of re-positioning and re-mounting the turbine on the rig is studied. The scope of this investigation is to reveal the effect of actuator placement relative to the structure. In conclusion, the current research paper is focused on addressing the variability of modal parameter estimation, which is critical due to the high sensitivity of turbomachinery against mistuning. It is shown that in the particularly demanding case of turbomachinery structural testing, small changes in a nominally defined modal testing workflow can lead to a quantifiable experimental variability. This variability could be detrimental to the reliable identification of the fatigue behaviour of blades.

Presenting Author: Theocharis Tsiris Loughborough University

Presenting Author Biography: Theocharis Tsiris is a Doctoral Researcher in the Department of Aeronautical and Automotive Engineering at Loughborough University. His research specializes in turbomachinery blade vibrations. He holds an MSc in Mechanical Engineering from Aristotle University of Thessaloniki, Greece. His experience includes professional work in rigid and flexible body dynamics simulation, as well as academic volunteering work on a Formula Student project. His primary interests lie in Experimental Modal Analysis, Structural Dynamics, Vibrations, Structural Analysis, Multibody Dynamics, and Finite Element Analysis.

Authors:

Theocharis Tsiris Loughborough University
Antonios Pezouvanis Loughborough University
Georgios Mavros Loughborough University
Marios Georgiou Loughborough University
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