University of Pretoria

David Hercules Diamond

Philippus Stephanus Heyns

Abraham Johannes Oberholster

A method () of determining blade tip deflection characteristics is applied to moving rotor blades (R, R) in a turbomachine () comprising a housing and rotor including a shaft with the rotor blades attached thereto and at least one proximity probe (). The method () includes measuring (() a proximity signal caused by a presence of a proximate tip of a moving rotor blade (R) and calculating () by a control module () a shaft Instantaneous Angular Position (IAP) as a function of time, and performing () an order tracking process which includes expressing () the measured proximity signal in the angular domain and resampling () the expressed proximity signal to render it equidistant in the angular domain. The method () includes performing () a pulse localisation process which includes filtering () the proximity signal yielding a complex-valued response, expressing () the complex-valued response in terms of a local amplitude and phase, and calculating () local phase shifts between each expressed signal and a reference signal.

Method and system for monitoring rotor blades of a turbomachine using blade tip timing (BTT)

A method () of measuring rotor blade tip deflections of turbomachine rotor blades (R, R) during operation using Blade Tip Timing (BTT) includes measuring (), by a proximity sensor (), a proximity signal caused by a moving rotor blade (R, R) and determining (), by a control module (), a Time-of-Arrival (ToA). The method () includes measuring a time that the shaft starts to rotate a measurable angular distance and a time the shaft has completed its rotation of the measurable distance and storing () timing data indicative of a plurality of ToA measurements of the rotor blade (R, R) and the zero crossing times. The method () includes determining the shaft Instantaneous Angular Position (IAP) between at least two zero crossing times, which determination comprises expressing the shaft IAP between at least two zero crossing times as a continuous, non-constant IAP mathematical function of time, with unknown function coefficients and calculating the unknown function coefficients of the IAP mathematical function.

Method and system for measuring rotor blade tip deflection using blade tip timing (BTT)

A method of estimating vibration characteristics of moving rotor blades in a turbomachine comprising a housing and rotor including a shaft with the rotor blades attached thereto includes measuring, by at least one proximity sensor, a Time-of-Arrival (ToA) of a proximate tip of a moving rotor blade. The method includes manipulating, by a control module, timing data to determine a corresponding blade tip deflection at each measured ToA, expressing blade tip vibration behaviour as a Bayesian statistical model consisting of intermediate model parameters, wherein model coefficients in the statistical model are probabilistic quantities as opposed to conventional, deterministic quantities, and expressing, by the control module, the determined blade tip deflections as observed values in the statistical model. The method includes manipulating the intermediate model parameters in the statistical model using Bayesian linear regression or inference to estimate the intermediate model parameters and consequently the vibration behaviour of the rotor blade.

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Pretoria, South Africa

David Hercules Diamond