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2 Vibrations in Physical Systems

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

100%

Pavolvskyi O. , Bouraou N.

tom Vol. 26

229--234

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.

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

80%

Bouraou N. , Pavlovskyi O. , Pazdrii O.

tom Vol. 27

61--66

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.