Rotordynamic Characteristics of a Flexure Pivot Pad Bearing With an Active and Locked Integral Squeeze Film Damper
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Measured rotordynamic coefficients are presented for a flexure-pivot-pad journal bearing (FPJB) in a load-betweenpad configuration with: (1) an active, and (2) locked integral squeeze film damper (ISFD). Prior rotordynamic- coefficient test results have been presented for FPJBs (alone), and rotorresponse results have been presented for rotors supported by FPJBS with ISFDs; however, these are the first rotordynamiccoefficient test results for FPJBs with ISFDs. A multi-frequency dynamic testing regime is employed. For both bearing configurations, quadratic curve fits provide good representation of the real portions of the dynamicstiffness coefficients yielding a direct stiffness and a direct added-mass coefficient. The imaginary portions are well represented by linear curve fits, implying constant, frequencyindependent direct-damping coefficients. Direct stiffness coefficients are ~50% lower for the active-damper configuration, and direct damping coefficients are only modestly lower. The combination of ~50% reduction in direct stiffness with a modest drop in direct damping indicates a very effective squeeze-film damper application. Added-mass coefficients are normally lower for the activedamper configuration, and all coefficient trends (for changes in loading and shaft speed) are "flatter" for the active flexure pivot-pad damper bearing. The measured rotordynamic coefficients are used to calculate the whirl frequency ratio and indicate high stability for both bearing configurations. Copyright © 2012 by ASME.
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