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Turbocharger Rotor-Bearing Design Optimization
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Sector:
Event:
1995 SAE Brasil
Language:
English
Abstract
Turbocharger rotor-bearing system needs to be optimized for durability, quietness, low power loss and low cost. The optimization is complicated because turbochargers are required to operate over a wide range of speed and bearing inlet pressure and temperature. The rotor and bearing impedance needs to be matched to obtain the best compromise between the shaft motion and bearing housing vibration. Impedance is the vector sum of the displacement dependent force, called “stiffness” and the velocity dependent resisting force called “damping”. These forces are at 90 degrees to each other. The shaft motion directly affects durability while the bearing housing motion impacts on turbocharger noise. The bearing friction loss can be reduced by reducing journal diameter and bearing length. Tests on bearing friction rig confirm the earlier findings that the difference in friction loss between semi-floating (non-rotating) bearing and fully floating (rotating) bearing is very small. Ball bearings have the best performance but their present cost limits their use as an alternative to the fully floating and the semi-floating bearings.
The present optimization procedure heavily relies on experiments. The cycle time and cost for developing an optimized rotor-bearing system may be significantly reduced by the use of computer programs. But accurate modeling of the bearing oil film characteristics i.e., dynamic stiffness, damping and mass properties, is very difficult due to non linear behavior of the bearing oil film. Experimentally determined bearing characteristics, combined with current Rotordynamics computer programs may provide acceptable results. A bearing test rig is under development at the author's company to improve the experimental determination of bearing characteristics under simulated operating conditions.
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Authors
Citation
Sahay, S., "Turbocharger Rotor-Bearing Design Optimization," SAE Technical Paper 952295, 1995, https://doi.org/10.4271/952295.Also In
References
- Sahay, Sunil N. Thouvenin, Denis Turbocharger Noise, Generating Mechanisms and Control Proceedings, International Noise and Vibration Conference 5 269 277 Interpublish Ltd. St. Petersburg,Russia 1993
- Trippet, Richard J. Measured and Predicted Friction in Floating-Ring Bearings SAE Technical Paper Series, # 860075 Society of Automotive Engineers, Inc. 400 Commonwealth Drive, Warrendale, PA. 15096 February 24-28 1986
- Flaxington, D Cooper, C.S Green, D.A. McCloy, S.W.S. A turbocharger bearing, dynamometer Proceedings of the Institution of Mechanical Engineers, Turbocharging and Turbochargers, ImechE 1994-6 321 330 Institution of Mechanical Engineers Birdcage Walk, London, UK
- Childs, Dara Hale, Keith A Test Apparatus and Facility to identify the Rotordynamic Coefficients of High-Speed Hydrostatic Bearings Journal of Tribology, Transactions of ASME 337 344 American Society of Mechanical Engineers 345 East 47 th Street, New York, NY 10017 April 1994