Abstract
Aimed at the vibration of whole aero-engine, a coupled dynamic model of rotor-ball bearing-stator of aero-engine is built. By means of the lumped mass method, taking into account the nonlinear rub-impact, bearing failure force and deformation of the casing, the dynamic equation of the system containing typical rub-impact is derived. The response of the system under different conditions is obtained by using the fourth order Runge-Kutta numerical integration algorithm. By adopting the finite element analysis software ANSYS, the finite element model of the rotor shaft is established and the first six-order natural frequencies of the rotor system are acquired. Taking advantage of the parameters of the signal in time domain and frequency domain, frequency characteristics are extracted as the fault features. The single-point rubbing experiment is carried out in the test rig, and the working speed is higher than the first critical speed, so the rotor shaft is flexible rotor. By the methods of spectrum and cepstrum analysis, the rub-impact characteristics of the casing vibration acceleration time series data are analyzed. The results show that the casing vibration acceleration has obvious impact characteristics; the impact frequency is equal to the product of rotating frequency and number of the blades; the impact frequency component and its multiple-frequencies are demonstrated in the frequency spectrum; the strength of impact is modulated by the rotating frequency, so that there are families of side bands on impact frequency and both sides of frequency doubling, and the interval of sideband equals the rotating frequency. The frequency components of the rotating frequency and its frequency doubling are clearly shown in the cepstrum. By comparing the simulation and experiment, the rubbing characteristics found out in this paper has enough accuracy.
Highlights
In rotating machinery, with the purpose of achieving the energy efficiency targets, it has been widely used to narrow the gap existing between the rotor and stator
When the rub-impact occurs between the rotor and stator, taking into account the transverse vibration of the rotor system, the differential equation governing the dynamical motion of the system based on barycenter motion theorem can be obtained as follows:
The application of comprehensive spectral analysis and cepstrum analysis by means of acceleration signal collected from test rig is carried out to extract the rub-impact features
Summary
With the purpose of achieving the energy efficiency targets, it has been widely used to narrow the gap existing between the rotor and stator. The main contribution of this work is summarized as follows: (1) by dint of waveforms, time-frequency spectrums, orbit trails, phase plane portrait and Poincare maps, etc., many kinetic characteristics of radial rub-impact are stated. These obtained characteristics have an significant effect on the diagnostics of rotor’s radial rub-impacts; (2) a rotor experiment rig is used to conduct the single-point rubbing experiments; the casing vibration acceleration signals are measured, by means of the casing acceleration signals’ analysis, the characteristics and laws of blade-casing rub-impact are found out; (3) the results by analyzing numerical simulated response signal and practical experimental vibration signal demonstrate that the rub-impact model has enough accuracy
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