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Research Papers: Gas Turbines: Structures and Dynamics

Dynamic Characterization of an Integral Squeeze Film Bearing Support Damper for a Supercritical Co2 Expander

[+] Author and Article Information
Bugra Ertas

Mechanical Systems,
GE Global Research Center,
Niskayuna, NY 12308

Adolfo Delgado

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

Jeffrey Moore

Machinery Section,
Southwest Research Institute,
San Antonio, TX 78238

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 3, 2017; final manuscript received August 8, 2017; published online November 14, 2017. Editor: David Wisler.

J. Eng. Gas Turbines Power 140(5), 052501 (Nov 14, 2017) (9 pages) Paper No: GTP-17-1261; doi: 10.1115/1.4038121 History: Received July 03, 2017; Revised August 08, 2017

The present work advances experimental results and analytical predictions on the dynamic performance of an integral squeeze film damper (ISFD) for application in a high-speed super-critical CO2 (sCO2) expander. The test campaign focused on conducting controlled orbital motion mechanical impedance testing aimed at extracting stiffness and damping coefficients for varying end seal clearances, excitation frequencies, and vibration amplitudes. In addition to the measurement of stiffness and damping, the testing revealed the onset of cavitation for the ISFD. Results show damping behavior that is constant with vibratory velocity for each end seal clearance case until the onset of cavitation/air ingestion, while the direct stiffness measurement was shown to be linear. Measurable added inertia coefficients were also identified. The predictive model uses an isothermal finite element method to solve for dynamic pressures for an incompressible fluid using a modified Reynolds equation accounting for fluid inertia effects. The predictions revealed good correlation for experimentally measured direct damping, but resulted in grossly overpredicted inertia coefficients when compared to experiments.

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References

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Figures

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Fig. 1

Sunshot sCO2 14 MW 27 krpm expander

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Fig. 2

Sunshot expander flexure pivot bearing w/ISFD

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Fig. 3

2π squeeze film damper configurations versus ISFD

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Fig. 4

Sunshot expander integral squeeze film damper test article

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Fig. 5

Experimental setup

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Fig. 6

Example dynamic excitation: 110 Hz at 0.75 mils peak vibration amplitude backward whirl

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Fig. 7

Physical (linearized) representation of ISFD force coefficients

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Fig. 8

Direct damping for various end seal clearances: 0.25 mil (6.35 μm) peak excitation amplitude

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Fig. 9

Direct damping for various frequencies and vibration amplitudes and vibratory velocity

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Fig. 10

Uncavitated versus cavitated ISFD

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Fig. 11

Real part of the transfer function and added inertia force coefficients (0.25 mil p–p excitation amplitude)

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Fig. 12

Integral squeeze film damper flow domain and boundary conditions used in numerical model

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Fig. 13

Pressure versus flow rate: ISOVG32 @ 120F

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Fig. 14

Top view of damper land showing velocity contour plot and flow streamlines. Steady-state CFD calculation using a commercial software. End seal clearance: 7.5 mils, supply pressure 20 psig.

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