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Improvement of the vibration diagnostics of rotation shaft damage based on fractal analysis

Bouraou N., Pavlovskyi O., Pazdrii O.

Vibrations in Physical Systems

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2016

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Vol. 27

61--66

EN

This work is devoted to further research and improvement of the vibration diagnostics of the initial crack-like damage of rotation shaft in aviation gas-turbine engines (GTE). We propose to use fractal analysis of the accelerating shaft response in order to increase the damage detection efficiency. Responses of the accelerating shaft are derived by using simulation in absence and in presence of the initial traverse crack. The responses of the cracked shaft have sub-critical peaks; the increase in size of a crack leads to the increase in peak values of the vibration amplitude in the range of sub-harmonic resonances. The Hurst exponent is obtained for the time series in the range of sub-harmonic resonances. The research shows that a small change in the crack size results in considerable change of the Hurst exponent, which allows to detect the mentioned sub-harmonic resonances of the measured signal in order to identify the initial crack-like damage of the rotation shaft.

2

On-board vibration diagnostics of shaft damage of the aviation engine

Pavolvskyi O., Bouraou N.

Vibrations in Physical Systems

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2014

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Vol. 26

229--234

EN

This work is devoted to the further researches and development a new on-board multilevel vibration control system of aviation gas-turbine engines (GTE). We propose to introduce new diagnosis level (subsystem) into development multilevel vibration control system for detection of the initial crack-like damage of rotor shaft. The proposed subsystem works at the non-steady-state modes of GTE, for example during startup at the acceleration to operating speed. The basis of this approach is the fact of the occurrence of sub harmonic resonances of accelerating cracked shaft response. It is necessary to extract the main rotor harmonic vibration at the nonsteady-state mode for crack diagnosis in practice. The narrow-band digital tracking filter is carried out for this aim, the central frequency of pass band is changing according the rotor rotation frequency. The efficiency of the proposed subsystem is demonstrated by the results of computer simulation.

3

Dynamika turbozespołu dużej mocy z pękniętym wirnikiem - symulacje komputerowe

Banaszek S.

Problemy Eksploatacji

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2005

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nr 3

121--130

PL

Praca przedstawia przebieg i wyniki badań symulacyjnych stanów dynamicznych maszyny energetycznej dużej mocy z pękniętym wirnikiem. Przedstawiono program NLDW służący do symulacji dynamiki maszyn wirnikowych oraz model maszyny wirnikowej - turbozespołu o mocy 200 MW. Pęknięcie zamodelowano za pomocą modelu Knotta. Badania obejmowały symulacje wpływu propagacji pęknięcia w określonym przekroju wirnika na dynamikę układu wirnikowego. W drugiej części, dla jednego z przypadków przeprowadzono symulacje wybiegu maszyny w zakresie prędkości obrotowych 1000÷3000 obr/min.

EN

Paper presents the course and results of the large power machine with cracked shaft. The researches were done in a way of computer simulations. An NLDW computer code is presented as well as a 200 MW turbo-set model. A crack is modeled with Knott model. The researches were concerning the crack propagation influence on the machine's dynamic state. A cracks were placed separately in the bearing no. 6 and in the middle of the generator shaft span. Four different angular positions were assumed (it gives different starting angle of the crack, different times of slot opening/closing and different phase angle between the slot and a force system resultant). It showed different and ambiguous crack influence on the machine's dynamics depending on crack location. A resonance as a function of crack depth propagation was discovered. In the second part of the work a run-down simulations were shown for different crack depths (close to the resonant crack depths values). A cascade diagrams were presented for bearing no. 6. They show very strong couplings between the slot effects and a rotor free vibrations. Those couplings may be utilized in a crack diagnostics.