Air Foil Bearing Review
Name: Naeem Nayfeh
Student id: S0917295
Module: Project Planning And Management
Module Code: MMH706486
Lecturer: Professor David Harrison
Project Planning & Management Assignment
Air Foil Bearing Review
All Air Foil Bearings (AFB) in general fit in one of two categories, hydrostatic and hydrodynamic.
Hydrostatic bearings require a pressurised air feed in order to lift of the foil surface but offer improved performance on start up and rundown [1] while developing no more drag than and equivalent hydrodynamic bearing.
Hydrodynamic bearings generate their air film purely through the rotation of the shaft. This independence of an external air supply has a significant impact on cost reduction but comes at the expense of increased wear at run-up and run-down [13].
An exception to this is a novel hybrid air foil bearing was recently proposed by Kim and Lee [20] which helps reduce wear during start up and shut down by combining a magnetic bearing with a hydrofoil. This allows the journal to be lifted clear of the top foil at start up and rundown then operated hydrodynamically once lift off speed has been exceeded. It also allows operation above the first bending critical speed by providing a method of increasing the stiffness and damping on request.
The benefits of Air Foil Bearings over traditional bearings has driven recent developments in the technology as their use was initially limited to small, low load high speed machines [3]. Benefits include low power consumption, lubricant free operation, long maintenance free life and the ability to withstand very high temperatures and high levels of vibration. They are however limited to a certain number of start/stops determined by the type of bearing and the amount of static load they are carrying due to rubbing during run up and run down.
This inherent limit does not halt the demand for greater loads and speeds in oil free machines which must be met by the manufactures. To meet these demands, the last
Student id: S0917295
Module: Project Planning And Management
Module Code: MMH706486
Lecturer: Professor David Harrison
Project Planning & Management Assignment
Air Foil Bearing Review
All Air Foil Bearings (AFB) in general fit in one of two categories, hydrostatic and hydrodynamic.
Hydrostatic bearings require a pressurised air feed in order to lift of the foil surface but offer improved performance on start up and rundown [1] while developing no more drag than and equivalent hydrodynamic bearing.
Hydrodynamic bearings generate their air film purely through the rotation of the shaft. This independence of an external air supply has a significant impact on cost reduction but comes at the expense of increased wear at run-up and run-down [13].
An exception to this is a novel hybrid air foil bearing was recently proposed by Kim and Lee [20] which helps reduce wear during start up and shut down by combining a magnetic bearing with a hydrofoil. This allows the journal to be lifted clear of the top foil at start up and rundown then operated hydrodynamically once lift off speed has been exceeded. It also allows operation above the first bending critical speed by providing a method of increasing the stiffness and damping on request.
The benefits of Air Foil Bearings over traditional bearings has driven recent developments in the technology as their use was initially limited to small, low load high speed machines [3]. Benefits include low power consumption, lubricant free operation, long maintenance free life and the ability to withstand very high temperatures and high levels of vibration. They are however limited to a certain number of start/stops determined by the type of bearing and the amount of static load they are carrying due to rubbing during run up and run down.
This inherent limit does not halt the demand for greater loads and speeds in oil free machines which must be met by the manufactures. To meet these demands, the last
References: 1. Kevin Radil & Michelle Zeszotek (2008), An Experimental Investigation into the Temperature Profile of a Compliant Air Foil Bearing, Tribology Transactions, 0569-8197, Taylor & Francis, 25 March 2008. 2. Luis San Andres & Tae Ho Kim (2008), Analysis of gas foil bearings integrating FE top foil models, Tribology International, 10.1016/j.triboint.2008.05.003, Elsevier Ltd, 4 May 2008. 3. Kyeong-Su Kim & In Lee (2007), Vibration Characteristics of a 75 kW Turbo Machine With Air Foil Bearings, Journal of Engineering for Gas Turbines and Power, 10.1115/1.2718220, ASME, 15 July 2007. 4. Louis San Andres (2010), Thermodynamic Analysis of Bump Type Gas Foil Bearings: A Model Anchored to Test Data, Journal of Engineering for Gas Turbines and Power, 10.1115/1.3159386, ASME, April 2010. 5. Manish Kumar & Daejong Kim (2009), Static performance of hydrostatic air bump foil bearings, Tribology International, 10.1016/j.triboint.2009.10.015, Elsevier Ltd, 30 October 2009. 7. Louis San Andres Dario Rubio Tae Ho Kim (2007), Rotordynamic Performance of a Rotor Supported on Bump Type Foil Gas Bearings: Experiments and Predictions, Journal of Engineering for Gas Turbines and Power, ASME, 10.1115/1.2718233, July 2007. 9. Hou Yu Chen Shuangtao Chen Rugang Zhang Qiaoyu & Zhao Hongli (2011), Numerical study on foil journal bearings with protuberant foil structure, Tribology International, Elsevier Ltd, 10.1016/j.triboint.2011.04.015, 7 May 2011. 11. V. Arora P. J. M. van der Hoogt R. G. K. M Aarts & A de Boer (2010), Identification of dynamic properties of radial air-foil bearings, Springer, 10.1007/s10999-010-9137-z, 21 October 2010. 12. Brian Dykas & Samuel A. Howard (2008), Journal Design Considerations for Turbomachine Shafts Supported on Foil Air Bearings, Tribology Transactions, Taylor & Francis, 10.1080/05698190490493391, 25 March 2008. 14. Luis San Andres & Tae Ho Kim (2008), Forced nonlinear response of gas foil bearing supported rotors, Tribology International, Elsevier, 10.1016/j.triboint.2007.12.009, 13 February 2008. 15. Yang Lihua Hu Deyi Liu Heng & Yu Lie (2008), Experimental Investigation on the Performance of Aerodynamic Compliant Foil Air Bearings, Proceedings of the IEEE, September 2008. 16. Y. Hou L. X. Xiong & C. Z. Chen (2004), Experimental Study of a New Compliant Foil Air Bearings with Elastic Support, Tribology Transactions, Taylor & Francis, 10.1080/05698190490490440911, 31 January 2004. 17. I. Ordanoff B. Bou Said A. Mezianne & Y. Berthier (2007), Effect of internal friction in the dynamic behaviour of aerodynamic foil bearings, Tribology International, Elsevier Ltd, 10.1016/j.triboint.2007.09.010, 13 September 2007. 19. J. F. Walton II & H. Hesmat (2002), Application of Foil Bearings to Turbomachinery Including Vertical Operation, Journal of Engineering for Gas Turbines and Power, ASME, 10.1115/1.1392986, October 2002. 20. Daejong Kim & Donghyun Lee (2010), Design of Three-Pad Hybrid Air Foil Bearing and Experimental Investigation on Static Performance at Zero Running Speed, Journal of Engineering for Gas Turbines and Power, ASME, 10.1115/1.4001066, September 2010.