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Research Papers: Gas Turbines: Structures and Dynamics

Analytic Modeling of Floating Ring Annular Seals

[+] Author and Article Information
Mihai Arghir, Manh-Hung Nguyen

Institut Pprime, CNRS UPR3346,  Université de Poitiers, 86962 Futuroscope Chasseneuil, France

David Tonon

SNECMA Space Engine Division, 27208 Vernon, France

Jérôme Dehouve

Centre National d’Etudes Spatiales, 91023 Courcouronnes Evry, France

Due to the use of the gradient type algorithm for solving the nonlinear algebraic system it is more correct to designate the present approach as quasi-analytic.

J. Eng. Gas Turbines Power 134(5), 052507 (Mar 01, 2012) (9 pages) doi:10.1115/1.4004728 History: Received May 29, 2011; Revised June 03, 2011; Published March 01, 2012; Online March 01, 2012

In order to avoid contact between the vibrating rotor and the stator, annular seals are designed with a relatively large radial clearance (∼100 μm) and, therefore, have an important leakage. The floating ring annular seal is able to reduce the leakage flow rate by using a much lower clearance. The seal is designed as a ring floating on the rotor in order to accommodate its vibrations. The pressure difference between the upstream and the downstream chambers is pressing the nose of the floating ring (secondary seal) against the stator. The forces acting on the floating ring are the resultant of the hydrodynamic pressure field inside the primary seal, the friction forces in the secondary seal, and the inertia forces resulting from the non-negligible mass of the ring. For proper working conditions, the ring of the annular seal must be able to follow the vibration of the rotor without any damage. Under the effect of the unsteady hydrodynamic pressure field (engendered by the vibration of the rotor), of the friction force, and of the inertia force, the ring will describe a periodic, a quasi-periodic, or a chaotic motion. Damage can come from heating due to friction in the secondary seal or from repeated impacts between the rotor and the ring. The present work presents an analytic model able to take into account only the synchronous periodic whirl motion of the floating ring.

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Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic design of a floating ring seal

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Figure 2

Fixed coordinate system and forces on the floating ring

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Figure 3

Trajectory of the rotor center (Jeffcot rotor supported by short bearings)

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Figure 4

Whirling coordinate system

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Figure 5

Geometry of the floating ring seal

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Figure 6

Dynamic coefficients of the annular seal (Pupstream  = 9 bars, Ω = 43 krpm)

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Figure 7

Amplitude of the floating ring whirl orbit

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Figure 8

Angle between the rotor and the floating ring

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Figure 9

Minimum film thickness

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Figure 10

Phase angle of the rotor center

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Figure 11

Transmitted effective stiffness and damping

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Figure 12

Working conditions of the floating ring

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Figure 13

Coordinate system and notations

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