Journal Bearing Lubrication Using Supercritical CO2 - A Theoretical Study

by Tim Dimond, Amir Younan, & Paul Allaire
University of Virginia, Rotating Machinery & Controls Laboratory

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Supercritical carbon dioxide (S-CO2) has been considered for use in applications where the process fluid has to be used as the fluid film journal bearing lubricant. This talk reviews the underlying theory of bearing lubrication, and considers the feasibility of S-CO2 as a bearing lubricant. The lubricating properties of S-CO2 in a tilting pad journal bearing are calculated using the ROMAC program MAXBRG. Rotordynamic performance metrics for a modified Jeffcott rotor, including undamped critical speeds, unbalance response, and stability margin, are compared for a theoretical S-CO2 lubricated tilting pad journal bearing (TPJB) design and a standard oil lubricated TPJB design. It is shown that acceptable rotordynamic performance can be achieved with a S-CO2 lubricated bearing with careful design. Experimental verification of the theoretical S-CO2 bearing characteristics is needed prior to use in industrial applications.