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Research Papers: Gas Turbines: Structures and Dynamics

Hermetically Sealed Squeeze Film Damper for Operation in Oil-Free Environments

[+] 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 77843, TX

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 2, 2018; final manuscript received August 29, 2018; published online October 15, 2018. Editor: Jerzy T. Sawicki.

J. Eng. Gas Turbines Power 141(2), 022503 (Oct 15, 2018) (9 pages) Paper No: GTP-18-1421; doi: 10.1115/1.4041520 History: Received July 02, 2018; Revised August 29, 2018

The following work advances a new concept for a hermetically sealed squeeze film damper (HSFD), which does not require an open-flow lubrication system. The hermetically sealed concept utilizes a submersed plunger within a contained fluidic cavity filled with incompressible fluid and carefully controlled end plate clearances to generate high levels of viscous damping. Although the application space for a hermetic damper can be envisioned to be quite broad, the context here will target the use of this device as a rotordynamic bearing support damper in flexibly mounted gas bearing systems. The effort focused on identifying the stiffness and damping behavior of the damper while varying test parameters such as excitation frequency, vibration amplitude, and end plate clearance. To gain further insight to the damper behavior, key dynamic pressure measurements in the damper land were used for identifying the onset conditions for squeeze film cavitation. The HSFD performance is compared to existing gas bearing support dampers and a conventional open-flow squeeze film dampers (SFD) used in turbomachinery. The damper concept yields high viscous damping coefficients an order of magnitude larger than existing oil-free gas bearing supports dampers and shows comparable damping levels to current state of the art open-flow SFD. The force coefficients were shown to contribute frequency-dependent stiffness and damping coefficients while exhibiting amplitude independent behavior within operating regimes without cavitation. Finally, using experimentally based force density calculations, the data revealed threshold cavitation velocities, approximated for the three end seal clearance cases. To complement the experimental work, a Reynolds-based fluid flow model was developed and is compared to the HSFD damping and stiffness results.

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Figures

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Fig. 1

Open-flow SFD versus HSFD

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Fig. 2

2π SFD configurations versus ISFD

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Fig. 3

Hermetic SFD test rig: standard views: (1) electro-hydraulic exciter, (2) static/dynamic force cell, (4) damper end plate, (5) damper housing, (6) pressure transducer, (7) proximity probe, and (8) accelerometer

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Fig. 4

Hermetic SFD test rig: cross section views: (4) damper end plate, (6) pressure transducer, (7) proximity probe, (8) accelerometer, (9) dynamic force transducer, (10) proximity probe target, (11) stinger, (12) flexible Ti diaphragm, (13) damper plunger, (14) damper centering spring, (15) upper cavity damper control volume, (16) lower cavity damper control volume, (17) end plate restriction gap, (18) shim, and (19) O-ring

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Fig. 5

Example experimental tests: 8 mi end plate clearance at 20 Hz and nominal 0.4 mi peak vibration

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Fig. 6

Static force deflection tests

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Fig. 7

Peak dynamic cavity pressures, dynamic pressure phase, and peak cavity force density

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Fig. 8

Hermetic SFD performance: experimental results with predictions including compressibility effects (2%, 4% gas volume fraction)

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Fig. 9

Experimental stiffness, damping, and threshold cavitation velocities for various end plate clearances

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Fig. 10

Damping comparison: HSFD versus existing oil-free damping solutions for gas bearings

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Fig. 11

Damping comparison: HSFD versus ISFD [22] single damper quadrant

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Fig. 12

Damper fluid temperature rise

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