Diagnosis of Partial Rotor- Stator Rubbing Using Variational Mode Decomposition

Abstract

Rotor-stator rubbing is occasional problem faced by rotating machines especially during startups and shut downs when passing through their critical speeds. The rubbing often occurs in rotating machinery at position with small clearances and can sometimes cause catastrophic breakdown of machine. So it is important to develop reliable tools for rub diagnosis. This paper investigates partial rub occurrence during constant and slightly variable speed operation and try to define vibration diagnosis patterns for its detection with Variational Mode Decomposition (VMD). The VMD is relatively new method with promising results potentially interesting for machinery failures diagnosis.. Diagnostic tool is tested on laboratory test rig at two different rotor operating conditions i.e. without rotor- stator rubbing and with partial rotor- stator rub. Measurements were performed with non-contact eddy current displacement sensors. Results are presented in the shape of VMD spectrograms and are compared to Empirical Mode Decomposition (EMD) spectrograms Rotor orbits are also presented to additionally verify rubbing condition.