A modal model for the experimental prediction of the stability threshold speed

• Published in: Applied Mathematical Modelling 2018-08, Vol.60, p.320-332
• Main Authors: Vervisch, B., Stockman, K., Loccufier, M.
• Format: Article
• Language: English
• Subjects: Aerospace industry; Computer simulation; Damping; Decay rate; Eigenvalues; Finite element analysis; Mathematical models; Modal model; Perturbation methods; Predictions; Rotating damping; Rotating machinery; Rotation; Rotordynamics; Stability; Stability threshold; Vibration
• ISSN: 0307-904X; 1088-8691; 0307-904X
• DOI: 10.1016/j.apm.2018.03.020

•The decoupling, by means of left and right eigenvectors of the multiple degree of freedom rotordynamic model is discussed.•The resulting single degree of freedom system is analysed and simplified by using perturbation analysis.•From this system, the decay rate and the corresponding stability threshold speed is derived.•The theory is validated through simulation and measurements. The stability threshold speed caused by rotating damping in rotating machinery is a limitation on the operating speed. The presence of the gyroscopic effect and rotating damping not only cause this unstable effect, both also result in difficulties to and to analyze the system. Although studied extensively in the past, the phenomenon is still difficult to model and validate experimentally. In this paper, a theoretical framework for the experimental validation is created by using the concept of a modal model combined with perturbation analysis. The concepts are validated by simulation and experiments which predict the stability threshold speed in three different situations of rotating damping. The simulation shows that the decay rate can be approximated by the modal model after simplification. Experiments show that the stability threshold speed can be predicted and that instability occurs close to this predicted speed.