Effects of Gas Entrainment on Squeeze Film Damper Performance

Abstract

Squeeze film dampers are frequently used for stabilization and/or vibration control of rotating machinery. Theoretical analyses to date generally assume an incompressible lubricant. In practice, however, depending on the capacity of the lubricant reservoir, the lubricant at damper inlet contains varying amounts of dissolved gas, which come out of solution to form a “spongy” gas-liquid mixture during damper operation. This paper examines theoretically and experimentally the effects such entrained gases have on damper performance, particularly on damper load capacity and the likelihood of multistable operation. It is shown that under certain operating conditions, a significant delay in the onset of bistable operation is predicted, depending on the fluid film model employed. Preliminary tests indicate that at low bearing parameter values (B ≐ 0.02), the homogeneous compressible film model using the Hayward rather than the Isbin viscosity relationship for gas-liquid mixtures provides the best prediction of damper performance. Of the incompressible film models, the zero pressure truncation predictions are generally quite satisfactory and superior to the commonly used π-film predictions.