Affiliation:
1. Assistant Professor Department of Mechanical Engineering, Hanyang University, Ansan, Gyeonggi-do 15588, South Korea e-mail:
2. Global Engineering Core Science, BorgWarner Turbo Systems, Arden, NC 28704 e-mail:
Abstract
Oil-free bearings for automotive turbochargers (TCs) offer unique advantages eliminating oil-related catastrophic TC failures (oil coking, severe bearing wear/seizure, and significant oil leakage, for example), while increasing overall system reliability and reducing maintenance costs. The main objective of the current investigation is to advance the technology of the gas foil bearings (GFBs) for automotive TCs by demonstrating their reliability, durability, and static/dynamic force characteristics desirable in extreme speed and temperature conditions. The paper compares drag friction and on-engine performances of an oil-free TC supported on GFBs against an oil-lubricated commercial production TC with identical compressor and turbine wheels. Extensive coastdown and fast acceleration TC rotor speed tests are conducted in a cold air-driven high-speed test cell. Rotor speed coastdown tests demonstrate that the differences in the identified rotational viscous drag coefficients and drag torques between the oil-free and production TCs are quite similar. In addition, rotor acceleration tests show that the acceleration torque of the oil-free TC rotor, when airborne, is larger than the production TC rotor due to the large mass and moment of inertia of the oil-free TC rotor even though air has lower viscosity than the TC lubricant oil. Separate experiments of the oil-free TC installed on a diesel engine demonstrate the reliable dynamic-forced performance and superior rotor dynamic stability of the oil-free TC over the oil-lubricated TC. The post on-engine test inspection of the oil-free TC test hardware reveals no evidence of significant surface wear between the rotor and bearings, as well as no dimensional changes in the rotor outer surfaces and bearing top foil inner surfaces. The present experimental characterization and verified robustness of the oil-free TC system continue to extend the GFB knowledge database.
Subject
Mechanical Engineering,Energy Engineering and Power Technology,Aerospace Engineering,Fuel Technology,Nuclear Energy and Engineering
Reference11 articles.
1. Bump-Type Foil Bearings and Flexure Pivot Tilting Pad Bearings for Automotive Oil-Free Turbochargers: Highlights in Rotordynamic Performance;ASME J. Eng. Gas Turbines Power,2016
2. On the Failure of a Gas Foil Bearing: High Temperature Operation Without Cooling Flow;ASME J. Eng. Gas Turbines Power,2013
3. Factors Influencing the Performance of Foil Gas Thrust Bearings for Oil-Free Turbomachinery Applications,2006
4. NASA PS400: A New High Temperature Solid Lubricant Coating for High Temperature Wear Applications,2009
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