Session: 28-02 Mistuning: Simulations & Experiments

Paper Number: 101993

101993 - Mistuning and Damping of a Radial Turbine Wheel. Part 3: Validation of Intentional Mistuning During Machine Operation 

The radial turbine impeller of an exhaust turbocharger is analyzed in view of both free vibration and forced response. Due to random blade mistuning resulting from unavoidable inaccuracies in manufacture or material inhomogeneities, localized modes of vibration may arise, which involve the risk of severely magnified blade displacements and inadmissibly high stress levels compared to the tuned counterpart. Contrary, the use of intentional mistuning (IM) has proved to be an efficient measure to mitigate the forced response.

In part one (GT2021-59283) of this three-part paper fundamental analyses have been carried out with the objective to find a suitable intentional mistuning pattern featuring only two different blade designs denoted as A and B. As a result of the analyses, the AABB sequence was identified to be the most promising one in terms of effecting a maximum forced response attenuation of the fundamental blade bending of more than 40% in theory. The second part (GT2022-80643) 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 efficiency 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. An approach to evaluate the raw-data namely times of arrival (TOA) without the availability of a once-per-revolution (OPR) signal is 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.

Presenting Author: Alex Nakos Brandenburg University of Technology

Presenting Author Biography: Alex Nakos is a research assistant at the Brandenburg University of Technology and deals with blade vibration of bladed compressors and turbines. Before that he worked as a design and computational engineer in a company that develops and manufactures the world's largest ship propellers.

Authors:

Alex Nakos Brandenburg University of Technology
Bernd Beirow Brandenburg University of Technology
Manfred Wirsum RWTH Aachen University
Markus Schafferus RWTH Aachen University
Marios Sasakaros RWTH Aachen University
Damian Vogt University of Stuttgart
Arthur Zobel University of Stuttgart