The Application of Gas-Lubricated Bearings to a Miniature Helium Expansion Turbine
In the production of refrigeration at liquid-helium temperatures, the use of an expansion engine or turbine eliminates the need for liquid-hydrogen precooling which would otherwise be required to precool helium below the inversion point prior to expansion through a valve. The extra complication introduced by the expander is usually justified by the elimination of the explosion and fire hazard associated with liquid hydrogen. In small machines it is customary to use an expansion engine because of the high speeds required of a turbine expander. These high turbine speeds are beyond the speed and life limits of conventional rolling element bearings. However, this limitation does not apply to gas-lubricated bearings. In a properly designed gas bearing the shaft can be maintained in a position of stable equilibrium so that it never touches the surface of the bearing. Thus, there is no rubbing friction and no wear; consequently, the bearing life should be indefinite and only the strength of the material limits the speed of a shaft supported on gas-lubricated bearings.
KeywordsInjector Hole Turbine Rotor Thrust Bearing Shaft Rotation Design Chart
Unable to display preview. Download preview PDF.
- 1.H. Sixsmith, “The Theory and Design of a Gas-Lubricated Bearing of High Stability,” Proceedings of First International Symposium on Gas-Lubricated Bearings, ACR-49. Office of Naval Research, Washington, D. C. (October, 1959).Google Scholar
- 2.H. Sixsmith, W. A. Wilson, and B.W. Birmingham, “Load-Carrying Capacity of Gas-Lubricated Bearings with Inherent Orifice Compensation Using Nitrogen and Helium Gas,” NBS Tech. Note 115 (August, 1961).Google Scholar
- 4.F. T. Barwell, Lubrication of Bearings, Butterworths Scientific Publications, London, England (1956) p. 168.Google Scholar
- 5.H. Sixsmith, “Bearings for Rotating Shafts which are Lubricated by Gas,” U.S. Patent No. 2,884,282 (April 28, 1959). British Patent No. 797,528.Google Scholar