EXPERIMENTAL INVESTIGATION OF THE DEVELOPMENT OF CAVITATION IN A SQUEEZE FILM DAMPER

When cavitation takes place in the squeeze film damper (SED), its types and extent affect the performance of the SFD significantly. Thus, a fundamental understanding of the incipience, formation and evolution of this phenomenon becomes important both for predicting the dynamic properties of the damper and for the practitioner designers. A test rig was set up to investigate the formation of the cavitation bubbles during the process of a steady-state operation. By adopting a crankshaft configuration, the SFD journal orbit can be fixed at a specified eccentricity. The journal position and its eccentricity are tracked by means of Bently proximity sensors. When cavitation takes place, its shape and evolution are recorded by a Photron APX-RS high speed camera. With the Dow Corning 200 lubricant, the gaseous bubbles form in a fern-leaf shape even at low whirling speed. The bubbles evolve to a miniature flattened shape and as the angular speed increases, the gaseous cavitation gives way or is joined by vaporous cavitation. With a further increase of whirling speed, the vaporous bubbles can be clearly seen to occupy a large area. The evolution of the cavitation can be explained by the Sommerfeld pressure curve as it relates to the gaseous and vaporous saturation pressure. The experimental results confirm the assumption made by these authors in the previous numerical simulations for the homogeneous cavitation models.