Session: 30-07 Mistuning

Paper Number: 80643

80643 - Mistuning and Damping of a Radial Turbine Wheel. Part 2: Implementation and Validation of Intentional Mistuning 

A 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 of this three-part paper fundamental analyses have been carried out to find a suitable intentional mistuning pattern which is featuring only two different blade designs [1]. This part is focused on the implementation and validation of the intentional mistuning pattern and discusses the detailed geometric adaption of the turbine wheel hardware. The final design of the geometric adaption is developed in terms of manufacturability and efficiency so that a reliable and robust solution is presented. Its machined adaption is validated by both vibration testing at rest and optical measurements so that manufacturing deviations are detected and their impacts discussed and evaluated. Reduced order models are built up for checking the effect of the implemented intentional mistuning pattern on the forced response by using the subset of nominal system modes (SNM) approach introduced by Yang and Griffin [2], which conveniently allows for accounting both the design intention of the mistuning pattern and the actually machined implementation due to manufacturing deviations.

[1] Nakos, A., Beirow, B. Zobel, A. Mistuning and Damping of a Radial Turbine Wheel. Part 1: Fundamental Analyses and Design of Intentional Mistuning Pattern. Journal of Engineering for Gas Turbines and Power, 18 August, 2021. https://doi.org/10.1115/1.4052201

[2] Yang, M. T., Griffin, J. H., “A Reduced-Order Model of Mistuning Using a Subset of Nominal System Modes”. Journal of Engineering for Gas Turbines and Power, 123, pp. 893-900 (2001)

Presenting Author: Alex Nakos Brandenburg University of Technology Cottbus

Presenting Author Biography: Master of Science in mechanical engineering and Ph.D. candidate at Brandenburg Technical<br/>University. Before that computational/design engineer at Mecklenburger Metallguss GmbH.

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