Multifrequency Response of a Squeeze Film Damper with Incipient Air Ingestion

Squeeze film dampers (SFDs) are essential in high-performance rotating machines, primarily to reduce vibration amplitudes at critical speeds and counteract destabilizing forces. A common issue in SFDs, especially with low supply pressures and non-tightly sealed axial ends, is air ingestion. This occurs when pressure gradients at the SFD’s axial ends allow air to enter, forming a bubbly oil mixture that reduces the damping coefficients. While past studies have focused on the effects of air ingestion on the response of SFDs subject to single-frequency excitations, its impact on the multifrequency response, which is critical for suppressing instabilities, has not been thoroughly explored. This study examines a large-clearance SFD with two inlet flow rates using single- and multifrequency excitations. Single-frequency tests involve frequencies from 10 Hz to 100 Hz, with orbit radii from 5% to 60% clearance ratios. The squeeze velocities range from 1 mm/s to 100 mm/s. The single-frequency t...