Application of coordinate transformation for detection of modes of vibration: A comparative study in 2 turbogenerators

Unlike the method of influence coefficients, modal balancing permits a reduction in the number of test runs in order to balance a rotodynamic system. This presents a great contribution to the area of turbomachinery, specifically in the reduction of offline time, as well as of economic losses as a direct consequence of the increased lifetime of the rotatory components. The success of modal balancing depends mainly on correct extraction of the modal parameters of the rotatory systems. One of the current limitations for the application of field balancing is the unreliability of the modal parameter extraction tools due the great quantity of information contained in the response diagrams added to the presence of close modes, which can generate confusion and provoke errors in the extraction process and modal identification. This work presents the development and application of two methodologies for the identification of the optimal modal parameters and close modes in the domain of frequency, applying the concept of coordinate transformation for rotatory systems. These methodologies were implemented separately in vibration signals from two field turbogenerators with the same technical and operational characteristics. © 2015, JVE INTERNATIONAL LTD.

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