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

Abstract

Air-gap eccentricity is one of the common faults of typical rotating machine, which results in a dynamic instability 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 modulation 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.

Keywords

• Rotating machine
• Air–gap eccentricity
• Multi-physical fields
• Signal demodulation
• Magnetic flux density
• Unbalanced magnetic pull