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research-article

Combined Airfoil and Snubber Design Optimization of Turbine Blades with Respect to Friction Damping

[+] Author and Article Information
Matthias Huels

Siemens AG, Mellinghofer Straße 55, 45473, Mülheim a. d. Ruhr, Germany
matthias.huels@siemens.com

Lars Panning-von Scheidt

Institute of Dynamics and Vibration Research, Leibniz University Hannover, 30167, Hannover, Germany
panning@ids.uni-hannover.de

Jörg Wallaschek

Institute of Dynamics and Vibration Research, Leibniz University Hannover, 30167, Hannover, Germany
wallaschek@ids.uni-hannover.de

1Corresponding author.

ASME doi:10.1115/1.4040679 History: Received March 01, 2018; Revised June 25, 2018

Abstract

A major concern for new generations of large turbine blades are forced and self-excited (flutter) vibrations which can cause high-cycle fatigue. The design of friction joints is a commonly applied strategy for systematic reduction of resonance amplitudes at critical operational conditions. In this paper, the influence of geometric blade design parameters onto the damped system response is investigated for direct snubber coupling. A simplified turbine blade geometry is parametrized and a well proven reduced order model for turbine blade dynamics under friction damping is integrated into a 3D Finite Element tool-chain. The developed process is then used in combination with surrogate modeling to predict the effect of geometric design parameters onto the vibrational characteristics. As such, main and interactions effects of design variables onto static normal contact force and resonance amplitudes are determined for a critical first bending mode. Parameters were found to influence the static normal contact force based on their effect on elasticity of the snubber, torsional stiffness of the airfoil and free blade untwist. The results lead to the conclusion that geometric design parameters mainly affect the resonance amplitude equivalent to their influence on static normal contact force in the friction joint. However, it is demonstrated that geometric airfoil parameters influence blade stiffness and are significantly changing the respective mode shapes, which can lead to lower resonance amplitudes despite an increase in static contact loads. Finally, an evolutionary optimization is carried out and novel design guidelines for snubbered blades with friction damping are formulated.

Copyright (c) 2018 by ASME
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