Measurements of pressure in a squeeze film damper with an air/oil bubbly mixture
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abstract
Squeeze film dampers (SFDs) provide damping to rotating machinery, thus reducing excessive vibration amplitudes, supressing instabilities, and isolating structural components. Large amplitude SFD journal motions while traversing critical speeds enhance the ingestion of air and lead to operation with a bubbly mixture of lubricant and air. This phenomena lacks firm analytical understanding and controlled tests presented here show its effect on SFD performance. The experiments report measurements of the dynamic pressure field in an SFD apparatus operating with a controlled bubbly mixture of oil and air. The journal describes circular-centered orbits at a fixed whirl frequency and the damper is fully submerged in an oil bath. The dynamic squeeze film pressures become less reproducible for consecutive cycles of journal orbital motion and the overall peak-to-peak film pressures decrease as the mixture void fraction (air/oil volume ratio) increases. An unstable zone of null squeeze pressure generation in the dynamic pressure fields, related to gas cavitation, becomes prevalent for mixtures with a large enough content of air. The power required to drive the SFD test rig decreases with increments in the air/oil volume ratio and, thus, provides evidence of a reduction in the mixture viscosity and damping capability of the test SFD. 1998 Taylor & Francis Group, LLC.
