Dynamic Stiffness and Damping Characteristics of a High-Temperature Air Foil Journal Bearing

Howard, S.A., Della Corte, C., Valco, M.J., Prahl, J.M. and Heshmat, H.  “Dynamic Stiffness and Damping Characteristics of a High-Temperature Air Foil Journal Bearing,” International Joint Tribology Conference, San Francisco, CA, October 21, 2001.

Using a high-temperature optically based displacement measurement system, a foil bearing’s stiffness and damping characteristics were experimentally determined.  Results were obtained over a range of modified Sommerfeld Number 1.5E6 to 1.5E7, and at temperatures from 25 to 538ºC. 

 

An Experimental procedure was developed comparing the error in two curve fitting functions to reveal different modes of physical behavior throughout the operating domain.  The maximum change in dimensionless stiffness was 3.0E-2 to 6.5E-2 over the Sommerfeld Number range tested.  Stiffness decreased with temperature by as much as a factor of two from 25 to 538ºC.  Dimensionless damping was a stronger function of Sommerfeld Number ranging from 20 to 300.  The temperature effect on damping being more qualitative, showed the damping mechanism shifted from viscous type damping to frictional type as temperature increased. 


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