A Full Spectrum Analysis Methodology Applied to an Anisotropic Overhung Rotor

Abstract

This paper demonstrates the methodology and usefulness of full spectrum analysis on theoretical models and experimental measurements. This method establishes another bridge between model and data that is not currently being used to its greatest advantage. Some experimental devices display full spectrum vibration signals but most often half spectrum is reported. Correlating analytical models with experimental data using full spectrum analysis is similarly underutilized.In this paper, 3D full spectrum plots from x and y signals (from either experimental or theoretical results) are shown to match very well with the plots generated by experimental ADRE software. Tracking filters are used to isolate synchronous and non-synchronous vibration and allow for accurate phase angle measurement. The strategy developed by this paper can accurately convert the math angle from theoretical model to experimental instrumentation phase angle. Then we draw direct comparison of experimental results of a flexible overhung rotor with theoretical results to estimate unknown system parameters such as bearing stiffness and skew angle due to the gyroscopic effect. Finally, our paper provides other significant results such as 3D orbit plots. The tools developed here directly connect the experiment to the theoretical model and can be used to verify theoretical models with greater confidence.

On post-resonance backward whirl in an overhung rotor with snubbing contact

“…They showed that under conditions when rotary inertia is high and the drive motor power is limited, the rotor system may have difficulty in passing through the critical speed, because much of the supplied energy will be transferred to the lateral vibration of the rotor instead of increasing its rotational speed. Wu et al [24] utilized a 4-DOF model for an overhung rotor with anisotropic supports to represent the experimental rig, which they used to validate their inhouse software for data processing and plotting full-spectrum cascade plots against those produced with commercial software. They were able to observe BW orbits that arise when passing through resonance, but did not investigate this phenomenon further as the focus of their work was on validation of their data processing software.…”