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TECHNICAL PAPERS: Gas Turbines: Heat Transfer

Analysis of Tangential-Against-Rotation Injection Lomakin Bearings

[+] Author and Article Information
Mihai Arghir

LMS,  Université de Poitiers, UFR Sciences SP2MI, Téléport 2, Blvd. Pierre et Marie Curie, BP 30719, 86962 Futuroscope Chasseneuil Cedex, Francemihai.arghir@lms.univ-poitiers.fr

Mathieu Hélène, Jean Frene

LMS,  Université de Poitiers, UFR Sciences SP2MI, Téléport 2, Blvd. Pierre et Marie Curie, BP 30719, 86962 Futuroscope Chasseneuil Cedex, France

J. Eng. Gas Turbines Power 127(4), 781-790 (Mar 01, 2003) (10 pages) doi:10.1115/1.1924632 History: Received October 01, 2002; Revised March 01, 2003

This work presents a thin film flow model for analyzing the static and dynamic characteristics of centered, eccentric or misaligned tangential-against-rotation injection Lomakin bearings. The Lomakin bearing is a recent device intended for use in modern turbomachinery and having characteristics similar to hybrid bearings. It can be described as an ensemble of two opposing straight annular seals separated by a circumferential feeding groove. The fluid is supplied to the groove via orifice restrictors. Their tangential inclination generates an against-rotation circumferential flow in the groove that further penetrates into the thin film. This effect, known from annular seals as the prerotation speed, improves the dynamic characteristics of the bearing. A good description of the flow in the circumferential groove and the thin film is obtained from a full Navier–Stokes calculation of the centered bearing. The zero and first order analyses are then carried out by recognizing the crucial importance of taking into account the interaction between the flow in the thin film lands, the circumferential groove and the supply orifices. Due to the high Reynolds number regime, the land flow is governed by the two-dimensional thin film inertia equations (the “bulk flow” model). A one-dimensional circumferential flow dominated by inertia forces is assumed to take place in the groove and is described by an appropriate bulk flow equation. The flows in the supply orifices, the groove and the thin film lands are linked together by the same mass flow rate balance algorithm as used for hydrostatic and hybrid bearings analysis. The algorithm is extended to Lomakin bearings by considering the groove areas surrounding each orifice as a row of intercommunicating feeding pockets. This approach enables the analysis of centered, eccentric or misaligned Lomakin bearings. Comparisons with water-lubricated test results are used to validate the present model. For the zero eccentricity case a good agreement is obtained for the cross-coupled stiffness and for the whirl frequency ratio. A parametric study shows the variation of the bearing characteristics with increasing static eccentricity or misalignment.

Copyright © 2005 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Lomakin bearing geometry and coordinate system

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Figure 8

Flow rate variation for centered working conditions

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Figure 7

The discretization of the circumferential groove of the Lomakin bearing

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Figure 6

Circumferential velocity in the Lomakin bearing (NS calculation)

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Figure 5

Axial velocity in the Lomakin bearing (NS calculation)

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Figure 4

Pressure variation in the Lomakin bearing (NS calculation)

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Figure 3

Computational domain used for the full Navier–Stokes calculation of the Lomakin bearing

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Figure 2

The geometric characteristics of the Lomakin bearing: (a) axial section, (b) circumferential section

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Figure 9

Direct stiffness for centered working conditions

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Figure 10

Cross-coupled stiffness for centered working conditions

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Figure 11

Direct damping for centered working conditions

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Figure 12

Cross-coupled damping for centered working conditions

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Figure 13

Direct added-mass for centered working conditions

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Figure 14

Whirl frequency ratio for centered working conditions

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Figure 15

Average circumferential velocity in the thin film land

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Figure 16

Variation of the flow rate with equivalent eccentricity

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Figure 17

Variation of the stiffness coefficients with equivalent eccentricity

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Figure 18

Variation of the damping coefficients with equivalent eccentricity

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Figure 19

Variation of the added mass coefficients with equivalent eccentricity

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