Patent ID: 8457909

Claim:
A method of analysing blade displacements detected by a plurality of circumferentially spaced stationary timing probes associated with an assembly of rotating blades mounted on a rotor, the blade displacements corresponding to times at which the blades pass the respective probes, the method comprising the step of: (a) identifying resonant vibration events in the assembly of rotating blades by performing the substeps of: (a-i) for each blade displacement detected by a timing probe, determining an associated running average blade displacement from a predetermined number of blade displacements detected by that probe for the same blade at adjacent rotations of the assembly, and subtracting the associated running average blade displacement from the blade displacement to calculate a corresponding zeroed blade displacement; (a-ii) determining, for successive rotations of the assembly, one or more correlation factors for respectively one or more of the blades, each correlation factor quantifying a degree of correlation between the zeroed blade displacement for a particular blade on a particular rotation and a modeled blade displacement corresponding to possible blade vibrational deflections on that rotation; and (a-iii) identifying, with a computer, a resonant vibration event within a rotation when one or more of the correlation factors cross a predetermined threshold; and (b) re-zeroing blade displacements on rotations identified with a resonant vibration event by performing the substeps of: (b-i) for each timing probe, determining a blade displacement offset from the average displacement of the predetermined number of blade displacements detected by that probe for the same blade at adjacent rotations of the assembly, all of which rotations are prior to the resonant vibration event, and (b-ii) for each blade displacement on a rotation identified with the resonant vibration event, replacing the previously-calculated corresponding zeroed blade displacement with an improved zeroed blade displacement calculated by subtracting from the blade displacement the respective blade displacement offset.