NDLI: Two-Dimensional Modeling of Shaft Precessional Motions Induced by Blade/Casing Unilateral Contact in Aircraft Engines

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Salvat, Nicolas Batailly, Alain Legrand, Mathias
Copyright Year	2014
Abstract	In the present work, the focus is made on the occurrence of precessional motions of the shaft — whirling motions — in bladed-disk assemblies, initiated by direct blade/casing contacts in one stage of an aircraft engine. These contact events are favored by increasingly reduced blade-tip clearances and are expected to occur during standard operating conditions. However, it has been shown that potentially harmful interactions may arise and threaten the engine structural integrity. A 2D in-plane model of an aircraft engine fan stage is built with a set of curved beams for the casing and an assembly straight beams for the bladed-disk. The flexibility of the shaft is reflected by two linear springs attached to the center node of the disk. Contact is initiated through a prescribed casing distortion and the two structures are then left free to interact. Equations of motion are solved via explicit time-marching and contact forces are computed with Lagrange multipliers method allowing to fully satisfy non-penetration conditions. Friction is accounted for through a Coulomb law and permanent sliding is assumed. Three types of regimes are identified, namely: (1) damped, (2) sustained, (3) divergent, and both forward and backward shaft precessional motions are witnessed. It is shown that the vibratory response of the bladed-disk mainly lies on the first nodal diameter of the first family of modes regardless of the rotational velocity or the type of regime detected. The risk of failure arising from these contact events is highlighted, in particular in the presence of forward whirl, and the need for accurate predictive tools in early design phases of the engine is emphasized.
Sponsorship	International Gas Turbine Institute
File Format	PDF
ISBN	9780791845776
DOI	10.1115/GT2014-25688
Volume Number	Volume 7B: Structures and Dynamics
Conference Proceedings	ASME Turbo Expo 2014: Turbine Technical Conference and Exposition
Language	English
Publisher Date	2014-06-16
Publisher Place	Düsseldorf, Germany
Access Restriction	Subscribed
Subject Keyword	Whirls Blades Risk Aircraft engines Equations of motion Modeling Engines Design Friction Disks Manufacturing Coulombs Springs Failure
Content Type	Text
Resource Type	Article

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