Modelling of magnetorheological oils in rotordynamic damping devices by bilinear material

0451912 - ÚT 2016 RIV SI eng C - Conference Paper (international conference)
Zapoměl, Jaroslav - Ferfecki, P. - Kozánek, Jan
Modelling of magnetorheological oils in rotordynamic damping devices by bilinear material.
Proceedings of ICoEV 2015. Ljublana: CTP National and University Library of Slovenia, 2015 - (Boltežar, M.), s. 563-570. ISBN 978-961-6536-97-4.
[International conference on engineering vibration. Lublaň (SI), 07.09.2015-10.09.2015]
R&D Projects: GA ČR GA15-06621S
Institutional support: RVO:61388998
Keywords : magnetorheological squeeze film damper * bilinear material * frequency response
Subject RIV: BI - Acoustics

To reduce lateral vibrations of rotors excited by unbalance of the rotating parts the damping devices are added to the rotor supports. To achieve their optimum performance their damping effect must be controllable. This is offered by magnetorheological squeeze film dampers whose damping force is produced by squeezing a thin layer of magnetorheological fluid between two concentric rings. The damping element is equipped with an electric coil that generates magnetic flux passing through the lubricating oil. As its resistance against the flow depends on magnetic induction, the change of the current can be used to control the damping force. The development of a new mathematical model of a magnetorheological squeeze film damper is based on assumptions of the classical theory of lubrication except that for the lubricant. Because the magnetorheological oils affected by a magnetic field belong to the class of liquids with a yielding shear stress, the lubricant is represented by a bilinear the-oretical material. The pressure distribution in the full oil film is then described by a modified Reynolds equation. In addition, the influence of cavitation and of the magnetic forces, by which the damping device acts on the rotor journal, were taken into account. The advantage of the developed mathematical model is that unlike the Bingham or Herschel-Bulkley materi-als the flow curve of the bilinear liquid is continuous. It reduces nonlinear character of the damping forces and thus rises numerical stability of the computational procedures. The simu-lations show that changing the magnetic induction in the lubricating film makes it possible to achieve the optimum performance of the damping device in a wide range of the rotor opera-tion speeds. The carried out calculations confirmed that application of the new model in-creased numerical stability of the simulation procedures.
Permanent Link: http://hdl.handle.net/11104/0255560