Parameter Identification of Bladed Assemblies Using a Subspace Method

This paper is aimed at identifying a dynamical model for bladed assemblies such as turbines. Unknown excitation forces are applied to bladed disk assemblies leading to forced vibration responses. Non contact measurement of such vibrations using tip-timing has become an industrial standard procedure and current research focuses on analysis methods for interpretation of measured vibrations. Our purpose is to develop a subspace method for the identification of blade's natural frequencies, damping ratios and mode shapes using blade tip-timing data. The importance of the developed procedure results in the fact that in a narrow band frequency, less than 2 Hz, twenty two modes can be easily identified. A detailed description of this method and results are presented.