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research-article

Thin gas film isothermal condensation in aerodynamic bearings

[+] Author and Article Information
Eliott Guenat

Rue De La Maladière 71b Neuchatel, 2002 Switzerland eliott.guenat@epfl.ch

Jurg Schiffmann

EPFL IMT LAMD Rue Jaquet Droz 1 Neuchâtel, 2002 Switzerland jurg.schiffmann@epfl.ch

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the Journal of Tribology. Manuscript received April 9, 2019; final manuscript received July 29, 2019; published online xx xx, xxxx. Assoc. Editor: Bart Raeymaekers.

ASME doi:10.1115/1.4044447 History: Received April 09, 2019; Accepted July 30, 2019

Abstract

High-speed small-scale turbomachinery for waste heat recovery and vapor compression cycles are typically supported on gas-lubricated bearings operating close to the saturation conditions of the lubricant. Under particular conditions, the gas film might locally reach the saturation pressure with potentially hazardous effects on the performance of the gas bearing. The present work introduces a model based on the Reynolds equation and the development of cavitation modeling in liquid-lubricated bearings for condensing gas bearings. The effect of condensation on load capacity and pressure and density profiles are investigated for three 1D bearing geometries (parabolic, Rayleigh step and wedge) and varying operating conditions. The results suggest that the load capacity is generally negatively affected if condensation occurs. An experimental setup consisting in a Rayleigh-step gas journal bearing with pressure taps to measure the local fluid film pressure is presented and operated first in air and then in R245fa in near-saturated conditions. The comparison between the evolution of the fluid film pressure under perfect gas and near saturation conditions clearly suggest the occurrence of condensation in the fluid film. These results are corroborated by the very good agreement with the model prediction.

Copyright © 2019 by ASME
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