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Research Papers: Gas Turbines: Structures and Dynamics

Compliant Hybrid Gas Bearing Using Modular Hermetically Sealed Squeeze Film Dampers

[+] 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

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 13, 2018; published online October 15, 2018. Editor: Jerzy T. Sawicki.

J. Eng. Gas Turbines Power 141(2), 022504 (Oct 15, 2018) (10 pages) Paper No: GTP-18-1422; doi: 10.1115/1.4041310 History: Received July 02, 2018; Revised August 13, 2018

This paper presents a new gas bearing concept that targets machine applications in the megawatt (MW) power range. The concept involves combining a compliant hybrid gas bearing (CHGB) with two hermetically sealed squeeze film damper (HSFD) modules installed in the bearing support damper cavities. The main aim of the research was to demonstrate gas bearing-support damping levels using HSFD that rival conventional open-flow squeeze film dampers (SFD) in industry. A detailed description of the bearing design and functionality is discussed while anchoring the concept through a brief recap of past gas bearing concepts. Proof-of-concept experimental testing is presented involving parameter identification of the bearing support force coefficients along with a demonstration of speed and load capability using recessed hydrostatic pads. Finally, a landing test was performed on the bearing at high speed and load with porous carbon pads to show capability of sustaining rubs at high speeds. The component testing revealed robust viscous damping in the bearing support, which was shown to be comparable to existing state of the art SFD concepts. The damping and stiffness of the system-portrayed moderate frequency dependency, which was simulated using a 2D Reynolds-based incompressible fluid flow model. Finally, rotating tests demonstrated the ability of the gas bearing concept to sustain journal excursions and loads indicative of critical speed transitions experienced in large turbomachinery.

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Figures

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Fig. 1

Past gas bearing concepts: (a) fixed geometry bearings, (b) external pressurized fixed geometry bearing, (c) actively pressurized fixed geometry bearing [10,11], (d) externally pressurized fixed geometry flexibly mounted bearings [12,13], (e) conventional bump foil bearing, (f) compliant hydrodynamic flexure pivot tilting pad bearing [16], (g) metal mesh foil bearing [20], (h) hybrid bump-foil metal mesh foil bearing [21], and (k) CHGB with MMD [1719]

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Fig. 2

Conventional open-flow SFD used in industry [25]

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Fig. 3

Equivalent damping versus stiffness ratio [17]

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Fig. 4

Conventional open flow SFD versus HSFD [28] integrated into a CHGB pad and housing

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Fig. 5

Compliant hybrid gas bearing with modular HSFD [29]: (1) bearing housing, (2) pad insert, (3) damper strut, (4) damper housing, (5) flexible elastomeric diaphragm and threaded stinger, (6) diaphragm retention disk, (7) damper end plate, (8) hydrostatic inlet tube, (9) film probe target, (10) hermetic SFD module, (11) upper damper cavity control volume, (12) lower damper cavity control volume, (13) damper restriction/gap, (14) damper plunger, (15) tilting pad integral spring KS, (16) compliant tilting pad, (17) rotor, (18) hybrid fluid film, (19) T/C or fill hole, (20) O-ring, (21) damper plug, and (22) damper centering spring

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Fig. 6

Experimental test setup for dynamic characterization of the bearing support: (1) damper plunger, (2) damper strut, (3) primary accelerometer, (4) stinger, (5) dynamic force transducer, (6) primary proximity probe, (7) secondary accelerometers, (8) bearing pad, (9) bearing pad integral “S” springs, (10) pad clamp, and (11) secondary proximity probes

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Fig. 7

Example test at 84 Hz: Pad 1 with dampers 1 and 3

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Fig. 8

Bearing support dynamic characterization: Stiffness and damping coefficients. Prediction approach from Ref. [28] for 1.5% GFV.

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Fig. 9

Open-flow ISFD [32] versus CHGB HSFD: damper details

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Fig. 10

Open-flow ISFD [32] versus CHGB w/HSFD: damping

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Fig. 11

Rotating test set-up: (a) motor, (b) test article, (c) rotor, (d) FWD end slave bearing pedestal, (e) AFT end slave bearing pedestal, (f) electrohydraulic exciter, (g) shear neck spool coupling, (h) slave bearings, (i) hydrostatic inlet fitting, (j) FWD/AFT end Y direction proximity probes, (k) Y direction dynamic force transducer, (l) X direction dynamic force transducer, (m) Y direction test article housing acceleration, (n) stinger, (o) FWD/AFT end X direction proximity probes, (p) pad TC’s, and (q) static loader

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Fig. 12

Dynamic translational orbital excitation at 8 krpm with hydrostatic recessed pads: excitation frequency 80 Hz; static bearing load 310 lbf (1.38 kN); inlet air pressure to bearing 175 psig (12 bar), bearing leakage 0.032 lbm/s (0.015 kg/s)

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Fig. 13

Bearing pad temperatures during translational orbital testing with hydrostatic recessed pads: excitation frequency 80 Hz; static bearing load 310 lbf (1.38 kN); inlet air pressure to bearing 175 psig (12 bar), bearing leakage 0.032 lbm/s (0.015 kg/s)

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Fig. 14

Dynamic conical motion testing: excitation frequency 140 Hz; static bearing load 310 lbf (1.38 kN); inlet air pressure to bearing 175 psig (12 bar), bearing leakage 0.032 lbm/s (0.015 kg/s)

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Fig. 15

Landing test on porous carbon pads: (1) bearing housing, (2) porous carbon pads: 14 krpm, static bearing load 310 lbf (1.38 kN); inlet air pressure to bearing 175 psig (12 bar)

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