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TECHNICAL PAPERS: Gas Turbines: Structures and Dynamics

A Bulk-Flow Model of Angled Injection Lomakin Bearings

[+] Author and Article Information
Luis San Andrés

Mechanical Engineering Department,  Texas A&M University, College Station, TX, 77843-3123lsanandres@mengr.tamu.edu

Thomas Soulas

Mechanical Engineering Department,  Texas A&M University, College Station, TX, 77843-3123

Patrice Fayolle

Snecma Moteurs—DMF,  Unités de Conception Turbomachines—FLTTR, Forêt de Vernon—BP 802, 27208 Vernon Cedex, France

The groove pressure approaches the supply pressure value as the rotor speed increases.

J. Eng. Gas Turbines Power 129(1), 195-204 (Mar 01, 2002) (10 pages) doi:10.1115/1.2227032 History: Received October 01, 2001; Revised March 01, 2002

This paper introduces a bulk-flow model for prediction of the static and dynamic force coefficients of angled injection Lomakin bearings. The analysis accounts for the flow interaction between the injection orifices, the supply circumferential groove, and the thin film lands. A one control-volume model in the groove is coupled to a bulk-flow model within the film lands of the bearing. Bernoulli-type relationships provide closure at the flow interfaces. Flow turbulence is accounted for with shear stress parameters and Moody’s friction factors. The flow equations are solved numerically using a robust computational method. Comparisons between predictions and experimental results for a tangential-against-rotation injection water Lomakin bearing show that novel model well predicts the leakage and direct stiffness and damping coefficients. Computed cross-coupled stiffness coefficients follow the experimental trends for increasing rotor speeds and supply pressures, but quantitative agreement remains poor. A parameter investigation shows evidence of the effects of the groove and land geometries on the Lomakin bearing flowrate and force coefficients. The orifice injection angle does not influence the bearing static performance, although it largely affects its stability characteristics through the evolution of the cross-coupled stiffnesses. The predictions confirm the promising stabilizing effect of the tangential-against-rotation injection configuration. Two design parameters, comprised of the feed orifices area and groove geometry, define the static and dynamic performance of Lomakin bearing. The analysis also shows that the film land clearance and length have a larger impact on the Lomakin bearing rotordynamic behavior than its groove depth and length.

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Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Angled injection Lomakin bearing and coordinate system

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Figure 2

Location and geometry of the feed orifices, groove, and film lands

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Figure 3

Dimensionless flowrate (Q) versus rotor speed and supply pressure conditions—tests and predictions (reference value: MSMP numerical)

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Figure 4

Dimensionless direct stiffness coefficients KXX=KYY versus rotor and supply pressure conditions—tests and predictions (reference value: MSMP numerical)

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Figure 5

Dimensionless cross-coupled stiffness coefficients KXY=−KYX versus rotor speed and supply pressure conditions—tests and predictions (reference value: MSMP numerical)

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Figure 6

Dimensionless direct damping coefficients CXX=CYY versus rotor speed and supply pressure conditions—tests and predictions (reference value: MSMP numerical)

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Figure 7

Dimensionless direct added-mass coefficient MXX=MYY versus rotor speed and supply pressure conditions—tests and predictions (reference value: MSMP numerical)

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Figure 8

Variation of dimensionless KXY=−KXY versus injection angle β—MSMP configuration (reference value: MSMP numerical)

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Figure 9

Variation of direct stiffness KXX=KYY versus GD parameter. Total orifice area (Aon) and groove area (Ag) change. MSMP configuration (reference value: MSMP numerical)

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Figure 10

Variation of cross-coupled stiffness KXY=−KYX versus GC parameter. Total orifice area (Aon) and groove length∕depth ratio (Lg∕Cg) change. MSMP configuration (reference value: MSMP numerical).

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