Harmonic modal analysis of hydroelectric runner in steady-state conditions: a Bayesian approach

Abstract

The characterization of hydroelectric turbine runners' dynamic behaviour is essential for accurate stress and fatigue life prediction leading to design and maintenance adapted to the fluctuating power demand. As the modal parameters of runners depend on the operating regime and coupling effects, a representative estimation of these parameters relies on the analysis of in-operation data. However, harmonics contained in Francis runners strain response complexify the use of traditional operational modal analysis methods. This paper proposes a steady-state harmonic modal analysis method using Non-Trivial Rotor-Casing Interactions (NTRCI). The Bayesian method used to identify the parameters is first presented. Then the method is evaluated on a ground truth system obtained with an analytically generated strain response and then deployed on operating runner strain gauge measurements. The paper concludes with a discussion and future works related to the exhaustivity of the proposed model and additional signal processing needs.

Keywords

• hydroelectric turbines
• synchronous vibrations
• operational modal analysis
• bayesian inference
• steady-state