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Research Papers: Gas Turbines: Structures and Dynamics

Bump-Type Foil Bearings and Flexure Pivot Tilting Pad Bearings for Oil-Free Automotive Turbochargers: Highlights in Rotordynamic Performance

[+] Author and Article Information
Keun Ryu

Assistant Professor
Department of Mechanical Engineering,
Hanyang University,
Ansan, Gyeonggi-do 15588, South Korea
e-mail: kryu@hanyang.ac.kr

Zachary Ashton

Global Engineering Core Science,
BorgWarner Turbo Systems,
Arden, NC 28704
e-mail: zashton@borgwarner.com

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 13, 2015; final manuscript received August 16, 2015; published online October 13, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(4), 042501 (Oct 13, 2015) (10 pages) Paper No: GTP-15-1275; doi: 10.1115/1.4031440 History: Received July 13, 2015; Revised August 16, 2015

Oil-free turbochargers (TCs) require gas bearings in compact units of enhanced rotordynamic stability, mechanical efficiency, and improved reliability with reduced maintenance costs compared with oil-lubricated bearings. Implementation of gas bearings into automotive TCs requires careful thermal management with accurate measurements verifying model predictions. Gas foil bearings (GFBs) are customarily used in oil-free microturbomachinery because of their distinct advantages including tolerance to shaft misalignment and centrifugal/thermal growth, and large damping and load capacity compared with rigid surface gas bearings. Flexure pivot tilting pad bearings (FPTPBs) are widely used in high-performance turbomachinery since they offer little or no cross-coupled stiffnesses with enhanced rotordynamic stability. The paper details the rotordynamic performance and temperature characteristics of two prototype oil-free TCs; one supported on foil journal and thrust bearings and the other one is supported on FPTP journal bearings and foil thrust bearings of identical sizes (outer diameter (OD) and inner diameter (ID)) with the same aerodynamic components. The tests of the oil-free TCs, each consisting of a hollow rotor (∼0.4 kg and ∼23 mm in OD at the bearing locations), are performed for various imbalances in noise, vibration, and harshness (NVH; i.e., cold air driven rotordynamics rig) and gas stand test facilities up to 130 krpm. No forced cooling air flow streams are supplied to the test bearings and rotor. The measurements demonstrate the stable performance of the rotor–gas bearing systems in an ambient NVH test cell with cold forced air into the turbine inlet. Post-test inspection of the test FPTPGBs after the hot gas stand tests evidences seizure of the hottest bearing, thereby revealing a notable reduction in bearing clearance as the rotor temperature increases. The compliant FPTPGBs offer a sound solution for stable rotor support only at an ambient temperature condition while demonstrating less tolerance for shaft growth, centrifugal, and thermal, beyond its clearance. The current measurements give confidence in the present GFB technology for ready application into automotive TCs for passenger car and commercial vehicle applications with increased reliability.

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References

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Figures

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Fig. 1

Gas bearings for oil-free TCs: (a) bump-type foil bearing [12] and (b) FPTPGB [13]

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Fig. 2

Prototype oil-free TC supported on gas bearings (CAD model and photograph of test hardware)

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Fig. 3

Schematic view with dimensions (mm) of test rotor, bearings, and BHs

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Fig. 4

Tests with journal GFBs (Core 1) in NVH test cell: effect of imbalances on rotor response. Waterfalls of rotor speed-down response. Measurement at compressor end nose, vertical plane. (a) Baseline (no added mass) and (b) added mass: 0.270 g mm at 0 deg angular location.

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Fig. 5

Tests with journal GFBs (Core 1) in NVH test cell: baseline response subtracted amplitude and phase angle of synchronous (1X) rotor response for three imbalance mass conditions of 0.141 g mm, 0.199 g mm, and 0.270 g mm. Masses inserted in 0 deg angular location on compressor nose. Measurement at compressor end nose, vertical plane.

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Fig. 6

Tests with journal FPTPGBs (Core 2) in NVH test cell: effect of imbalances on rotor response. Waterfalls of rotor speed-down response. Measurement at compressor end nose, vertical plane. (a) Baseline (no added mass) and (b) added mass: 0.270 g mm at 0 deg angular location.

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Fig. 7

Tests with journal FPTPBs (Core 2) in NVH test cell: baseline response subtracted amplitude and phase angle of synchronous (1X) rotor response for three imbalance angular locations of 0 deg, 120 deg, and 240 deg on compressor nose with 0.270 g mm. Measurement at compressor end nose, vertical plane.

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Fig. 8

Tests with journal GFBs (Core 1) in NVH test cell: effect of speed-up and speed-down. Overall and filtered, synchronous (1X) and subsynchronous (sub-1X), amplitudes of rotor whirl motions versus rotor speed. Measurement at compressor end nose, vertical plane. Baseline imbalance. (a) Speed-up. Ramp rate ∼670 rpm/s. (b) Speed-down. Ramp rate ∼400 rpm/s.

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Fig. 9

Tests with journal FPTPGBs (Core 2) in NVH test cell: effect of speed-up and speed-down. Overall and filtered, synchronous (1X) and subsynchronous (sub-1X), amplitudes of rotor whirl motions versus rotor speed. Measurement at compressor end nose, vertical plane. Baseline imbalance. (a) Speed-up. Ramp rate ∼400 rpm/s. (b) Speed-down. Ramp rate ∼400 rpm/s.

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Fig. 10

Tests with GFBs (Core 1) in NVH test cell. 20 °C turbine inlet temperature: recorded journal and thrust bearing temperatures versus elapsed time with rotor spinning from 60 krpm to 100 krpm. Baseline imbalance.

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Fig. 11

Tests with GFBs (Core 1) in gas stand test cell. 400 °C turbine inlet temperature. Baseline imbalance. Measurement along vertical plane. (a) Waterfall. Acceleration on BH outer surface. (b) Amplitudes of synchronous and subsynchronous vibrations. Acceleration on BH outer surface. (c) Waterfall. Shaft motion at compressor nose end.

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Fig. 12

Tests of a production TC supported on fully floating ring bearings in gas stand test cell. 400 °C turbine inlet temperature. Baseline imbalance. Measurement along vertical plane. (a) Waterfall. Acceleration on BH outer surface. (b) Amplitudes of synchronous and subsynchronous vibrations. Acceleration on BH outer surface.

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Fig. 13

Tests with GFBs (Core 1) in gas stand test cell. 350 °C turbine inlet temperature: recorded journal and thrust bearing temperatures versus elapsed time with rotor spinning from 60 krpm to 100 krpm. Baseline imbalance.

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Fig. 14

Tests with FPTPBs (Core 2) in gas stand test cell. 350 °C turbine inlet temperature: (a) rotor speed versus elapsed test time and (b) waterfall of rotor response along compressor nose vertical plane. Data for operation from 0 to ∼33 min elapsed test time (i.e., data from 0 to 70 krpm) not shown.

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Fig. 15

Tests in gas stand test cell. Turbine inlet temperature 350 °C. TC overall efficiency versus compressor pressure ratio on a total-to-static basis for oil-free TC supported on GFBs (Core 1) and production TC supported on oil-lubricated floating ring bearings. Baseline imbalance.

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