Periodically non-stationary properties of vibrations for gas-turbine engine with unbalanced rotor
“The low-frequency vibrations (<2 kHz) of gas-turbine engine are analyzed onthe basis of their model in the form of periodically non-stationary randomprocesses (PNRP). It is shown that the power spectrum of the raw signal ismixed. The least square method is used for discovering of the hiddenperiodicities of the first and second orders. The frequencies of the deterministicbasic harmonics are estimated and amplitude and power spectra of thedeterministic oscillations are found. These spectra are compared for the cases ofbalanced and unbalanced rotors. It is show that the power on the first harmonicfor the unbalanced rotor is dominant. The interpolation formulas for the timedependences of PNRP mean function are obtained and the vibration stochasticparts are separated. It is revealed that for unbalanced rotor the variance is thetime periodical function, basic frequency of which is closed to the rotationfrequency. This properties is caused by the appearance of the distribute fault.”