Full three-dimensional investigation of structural contact interactions in turbomachines

Mathias Legrand (1) , Alain Batailly (1) , Benoit Magnain (2) , Patrice Cartraud (3) , Christophe Pierre (1)

1 Structural Dynamics and Vibration Laboratory [Montréal]
2 PRISME - Laboratoire Pluridisciplinaire de Recherche en Ingénierie des Systèmes, Mécanique et Energétique
3 GeM - Institut de Recherche en Génie Civil et Mécanique

Minimizing the operating clearance between rotating bladed-disks and stationary surrounding casings is a primary concern in the design of modern turbomachines since it may advantageously affect their energy efficiency. This technical choice possibly leads to interactions between elastic structural components through direct unilateral contact and dry friction, events which are now accepted as normal operating conditions. Subsequent nonlinear dynamical behaviors of such systems are commonly investigated with simplified academic models mainly due to theoretical difficulties and numerical challenges involved in non-smooth large-scale realistic models. In this context, the present paper introduces an adaptation of a full three-dimensional contact strategy for the prediction of potentially damaging motions that would imply highly demanding computational efforts for the targeted aerospace application in an industrial context. It combines a smoothing procedure including bicubic B-spline patches together with a Lagrange multiplier based contact strategy within an explicit time-marching integration procedure preferred for its versatility. The proposed algorithm is first compared on a benchmark configuration against the more elaborated bi-potential formulation and the commercial software Ansys. The consistency of the provided results and the low energy fluctuations of the introduced approach underlines its reliable numerical properties. A case study featuring blade-tip/casing contact on industrial finite element models is then proposed: it incorporates component mode synthesis and the developed 3D contact algorithm for investigating structural interactions occurring within a turbomachine compressor stage. Both time results and frequency-domain analysis emphasize the practical use of such a numerical tool: detection of severe operating conditions and critical rotational velocities, time-dependent maps of stresses acting within the structures, parameter studies and blade design tests.

Mots clés: Contact dynamics; nonlinear dynamics; Lagrange multipliers; surface B-spline; modal synthesis; time-marching techniques

Domaines: Génie mécanique [physics.class-ph]; Génie mécanique [physics.class-ph]; Mécanique des structures [physics.class-ph]; Mécanique des structures [physics.class-ph]

Mathias Legrand, Alain Batailly, Benoit Magnain, Patrice Cartraud, Christophe Pierre. Full three-dimensional investigation of structural contact interactions in turbomachines. Journal of Sound and Vibration, 2012, in press. ⟨hal-00660863v2⟩