Parametric excitation and antiresonance in rotating systems with gas bearings

Δήμου, Εμμανουήλ; Dimou, Emmanouil

dc.contributor.author	Δήμου, Εμμανουήλ	el
dc.contributor.author	Dimou, Emmanouil	en
dc.date.accessioned	2022-11-21T09:32:56Z
dc.date.available	2022-11-21T09:32:56Z
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/56193
dc.identifier.uri	http://dx.doi.org/10.26240/heal.ntua.23891
dc.rights	Αναφορά Δημιουργού-Μη Εμπορική Χρήση 3.0 Ελλάδα	*
dc.rights.uri	http://creativecommons.org/licenses/by-nc/3.0/gr/	*
dc.subject	Parametric excitation	en
dc.subject	Antiresonance	en
dc.subject	Gas Foil Bearings	en
dc.subject	Rotating shafts	en
dc.title	Parametric excitation and antiresonance in rotating systems with gas bearings	en
heal.type	bachelorThesis
heal.classification	Dynamics of rotating machines	en
heal.language	en
heal.access	free
heal.recordProvider	ntua	el
heal.publicationDate	2022-07-14
heal.abstract	Parametric excitation is applied in a realistic multi-segmented rotating shaft of a turbopump mounted on two active gas foil bearings. The active configuration of the two gas foil bearings is defined by a periodic external load of specific amplitude and frequency which alternates the top foil configuration and in this manner the gas film impedance forces experience periodic variation. The analytical model of the rotor is obtained using a reduced Finite Element model, and the Reynolds equation for the compressible flow of the gas is solved applying a reduced Finite Difference scheme. Fully balanced rotors are investigated on their potential to shift the threshold speed of instability defined by the rotating speed at which the first bifurcation of limit cycles occurs. The limit cycles are evaluated through pseudo arc length continuation with an embedded collocation method. The respective amplitude and frequency of applied external excitation (parametric excitation) is investigated in order to define those characteristics (amplitude and frequency) which render parametric antiresonance in the rotating system. Two approaches are included. At the first, the parametric excitation is implemented in the system, through periodically varying stiffness and damping coefficients of the gas foil bearings, which are evaluated solving the perturbed Reynolds equation. At the second, direct implementation of gas bearing impedance forces is considered. Comparing the two approaches, it is found that antiresonance occurs in specific excitation frequencies, and the rotating system operates without bifurcation at speeds two times higher than the respective speed of the reference system without excitation. Several design scenarios for rotor slenderness and bearing configuration are included in the results.	en
heal.sponsor	The work in this paper is outcome of the ongoing research synergy between National Technical University of Athens and Karlsruhe Institute for Technology, entitled “Nonlinear Dynamics of Rotor Systems with Controllable Bearings”, funded by the Alexander von Humboldt Foundation.	en
heal.advisorName	Χασαλεύρης, Αθανάσιος	el
heal.committeeMemberName	Κουλοχέρης, Δημήτριος	el
heal.committeeMemberName	Αντωνιάδης, Ιωάννης	el
heal.committeeMemberName	Χασαλεύρης, Αθανάσιος	el
heal.academicPublisher	Εθνικό Μετσόβιο Πολυτεχνείο. Σχολή Μηχανολόγων Μηχανικών. Τομέας Μηχανολογικών Κατασκευών και Αυτομάτου Ελέγχου	el
heal.academicPublisherID	ntua
heal.numberOfPages	67 σ.	el
heal.fullTextAvailability	false