Modulation characteristics of multi-physical fields induced by air-gap eccentricity faults for typical rotating machine

Air-gap eccentricity is one of the common faults of typical rotating machine, which results in a dynamic insta-bility state of multi-physical fields. To investigate the muti-physical instabilities of rotating machine under air-gap eccentricity fault, combining numerical and experimental methods were applied. The electromagnetism simulations were conducted to calculate magnetic flux density and unbalanced magnetic pull. The signal acquisition including magnetic flux density, vibration acceleration, and pressure fluctuation were conducted to muti-physical coupling experiment. The modulation characteristics caused by air-gap eccentricity were extracted with a signal demodulation method based on principle component analysis. The results indicate that modulation effects of the rotating frequency (fs) and twice the rotating frequency (2 fs) generated by the magnetic field were transmitted to the structure field and flow field. In the demodulation results of pressure pulsation, the modu-lation effect of blade passing frequency near the pump inlet was enhanced. Correlations between the instability of magnetic field, structure field, and flow field are determined to develop monitoring, detection, and diagnosis for rotating machine system, while the modulation characteristics of muti-physical field signals can serve as indicators of instabilities.

Automated summary

This study investigates the multi-physical instabilities of rotating machines under air-gap eccentricity fault using numerical and experimental methods. Electromagnetic simulations are carried out to calculate magnetic flux density and unbalanced magnetic pull. Signal acquisition and demodulation methods are employed to extract the modulation characteristics. The results show that the instabilities can be monitored and diagnosed using the modulation characteristics of multi-physical field signals.