Study of dual-shaft gas turbine engine inter-rotor bearing vibrations at slow rotor rotation

Аuthors

Zvonarev S. L.^1*, Klyagin S. V.², Potapov A. Y.²

1. Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia
2. Gas turbine engineering research and production center Salyut, 16, Budennogo av., Moscow, 105118, Russia

*e-mail: zvonarev@umail.ru

Abstract

The purpose of this work consists in clarification and generalization of two-shaft gas turbine engine rolling bearings vibration diagnostics method. The paper gives the review of the well-known problems associated with gas turbine engine rolling bearings vibration diagnostics, and considers methods employed while carrying out diagnostics. We sel ected the procedure using hand rolling of one of the engines' rotors for our studies. The paper considers possible problems occurring during diagnostics. For the studies we assume the same frequency range that is used while hand rolling. The vibration signal measured prior to the complete stop of the engine is generated under identical conditions. Such conditions are characterized by very low forces, causing forced oscillations. Thus, we can neglect these oscillations. The signal for the study carrying out was obtained fr om the engine with damaged bearing. The degree of the damage development was rather high. The rotor decrease in speed, and short time interval do not allow employ conventional rolling bearings spectral vibration diagnostics methods. Analysis of the signal temporal realization reveals the absence of considerable shock load. Spectral analysis reveals the presence of only one significant harmonic in coincidence with the engines natural frequency. this natural frequency is characterized by the high value of deformation latent energy accumulated in in the bearing. The absence of the shock load points out that natural oscillations excitation does not occur. The inference is drawn on the presence of self-sustained oscillations in rotor rundown mode, developed at natural frequency. As long as the oscillating processes in the engine are almost finished, the natural oscillations cannot obtain energy for the amplitude rise. In view of natural oscillations amplitude smallness their impact on bearing degradation is insignificant. Self-sustained oscillations process phase diagrams are plotted. Strap brake is a literary analogue of the being obtained self-sustained oscillation system. Despite the vibration signal non-stationarity, spectral analysis allows obtain reliable diagnostic results. The conclusion has been drawn about the possibility of applying the considered phenomenon for vibration diagnostics of roller bearing dual-shaft gas turbine engines.

Keywords:

vibration diagnostics, gas-turbine engine inter-rotor roller bearing, spectral analysis, nonlinear vibrations

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