The Effect of O-Ring Compression Set on the Rotordynamic Behavior of Turbomachinery

For some aerospace applications, radial load support for high-speed turbomachinery is provided by gas foil journal bearings mounted on elastomeric O-rings. O-ring mounting provides several benefits including energy dissipation, thermal growth compensation, and higher bore misalignment tolerance. O-ring material selection requires careful consideration of application-specific factors to properly manage the synchronous and sub-synchronous response of the rotor bearing system over the lifetime of the application. O-ring material stiffness, bearing stiffness, operating temperatures, and environmental exposure are all relevant factors. Long-term exposure to operating environments can result in evolution of O-ring properties over time, including changes in stiffness, damping, and permanent compression set. The objective of this work was to empirically characterize O-ring compression set behavior for a range of materials at a subscale level and to evaluate the associated effects on rotordynamic behavior at the assembly level. Subscale characterization efforts identified two materials with unique characteristics which were selected for further evaluation via full-scale assembly level rotordynamic testing. O-ring material characterization and high-speed rotordynamic test results are quantitatively evaluated, compared, and discussed to assess the suitability for use in future applications. Additional opportunities for continued validation efforts are also discussed.