Squeeze film dampers (SFDs) with low levels of external pressurization and poorend sealing are prone to air entrapment, thus reducing the damping capability.Furthermore, existing predictive models are too restrictive. Single frequency,unidirectional load and centered circular orbit experiments were conducted on arevamped SFD test rig. The damper journal is 1" in length and 5" in diameter, withnominal clearance of 5 mils (0.127 mm). The SFD feed end is flooded with oil, whilethe discharge end contains a recirculation groove and four orifice discharge ports toprevent air ingestion. The discharge end is fully sealed with a wave-spring that pushes aseal ring into contact with the SFD journal. The measurements conducted without andwith lubricant in the squeeze film lands, along with a frequency domain identificationprocedure, render the mechanical seal dry-friction force and viscous damping forcecoefficients as functions of frequency and motion amplitude. The end seal arrangementis quite effective in eliminating side leakage and preventing air entrainment into the filmlands. Importantly enough, the dry friction force, arising from the contact forces inrelative motion, increases significantly the test element equivalent viscous dampingcoefficients. The identified system damping coefficients are thus frequency andamplitude of motion dependent, albeit decreasing rapidly as the motion parametersincrease. Identified force coefficients, damping and added mass, for the squeeze filmdamper alone agree very well with predictions based on the full film, short length SFDmodel.
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