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Abstract

A system and method are provided for monitoring synchronous blade vibration in a turbo-machine. At least three sensors capable of detecting the arrival of each blade are arranged about the cylinder which surrounds the tips of the blades. The location of the sensors is selected to minimize the influence of errors in the data. To this end, and to simplify the installation of the sensors into the cylinder, the sensors may be non-uniformly spaced. The location of each sensor for purposes of constructing Fourier transforms is determined using the arrival times at the blades at each sensor, expressed as a fraction of a rotor revolution. The transform matrix is constructed for a predetermined discrete set of M harmonics, so that M harmonics are analyzed simultaneously, the number of harmonics which can be simultaneously analyzed is related to the number of sensors used. The blade arrival time data at each sensor, expressed as a fraction of a rotor revolution, is analyzed to determine the amplitude of the blade vibration at each of the harmonics selected for the set. The calculations are repeated for a variety of harmonic sets in order to accurately interpret the results in the event there is significant vibration at harmonics not included in the initial set.

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