Effect of multi-frequency parametric excitations on the dynamics of on-board rotor-bearing systems

• Published in: Mechanism and machine theory 2020-03, Vol.145, p.103660, Article 103660
• Main Authors: Briend, Yvon, Dakel, Mzaki, Chatelet, Eric, Andrianoely, Marie-Ange, Dufour, Régis, Baudin, Sophie
• Format: Article
• Language: English
• Subjects: Dynamic instability; Engineering Sciences; Finite element method; Hydrodynamic journal bearing; Mechanics; On-board rotor; Parametric excitation; Physics; Rotordynamics; Support motions; Vibrations
• ISSN: 0094-114X; 1873-3999
• DOI: 10.1016/j.mechmachtheory.2019.103660

•A new FE model is proposed to assess the role of support motions in on-board rotordynamics.•This model is based on the Timoshenko beam theory and six DOFs.•A parametric influence is generated by the rotations and the translations of the support.•This influence creates single-frequency and multi-frequency parametric excitations.•The dynamic stability of the rotor is evaluated through the Floquet theory. In the transportation domain such as automotive turbochargers and aircraft turbines, the vibrations of on-board rotors are induced not only by the mass unbalance excitation but also by various movements of their support. The dynamics of an on-board rotor mounted on hydrodynamic finite-length bearings is investigated in the presence of support motions which create multi-frequency parametric excitations. The developed on-board rotor model is based on the gyroscopic Timoshenko beam finite element with two nodes and six degrees of freedom per node for 3D motions (transverse and axial displacements as well as rotations due to the bending and to the torsion). The equations of motion highlight time-varying parametric terms due to the mass unbalance, the support rotations, the coupling between both phenomena and the combination of mass unbalance and support translations. These parametric terms can yield a dynamic instability because they contribute as generators of internal excitation. In the presented applications, single-frequency and multi-frequency parametric excitations are used. Namely, the rotor is excited either by simple and combined sinusoidal support rotations or by a rotating mass unbalance combined with sinusoidal support translations to examine the stability of the static equilibrium point through the Floquet theory.