EXPERIMENTAL INVESTIGATION OF VIBRATION CHARACTERISTICS FOR VAPOR CAVITATION EROSION IN PLAIN JOURNAL BEARING

The phenomenon of vapor cavitation in hydrodynamic bearings and its detrimental
effects have been documented in many literatures. Collapse of vapor cavitation
bubbles may cause erosion wear that limits the life of the bearings. The ability to
detect the occurrence of vapor cavitation using a well established condition
monitoring technique is essential for the equipment operator. The occurance of vapor
cavitation, particularly in elliptical journal bearings, is not well reported in literature.
An experiment was therefore conducted to investigate the vibration characteristics of
vapor cavitation erosion in steadily loaded, elliptical journal bearings of a running
gearbox. Vibration data were collected from the bearings operating under the
influence of vapor cavitation erosion. The results showed that, vapor cavitation
erosion exhibit distinct characteristics on the vibration plots. Low amplitude, forward
and reverse 0.063X frequency components, and a series of harmonics with
frequencies lower than 0.5X, were observed on the full spectrum. A unique,
asymmetrical waveform with the positivepeakamplitude fluctuating above and below
the zero axis line was also observed. The whirling shaft was also unstable under the
vaporcavitation condition. When the vaporcavitation was removed by increasing the
oil supply flow and pressure, the subsynchronous vibration components lower than
0.5X were not seen on the full spectrum. The waveform was symmetrical and the
whirling shaft was also stable without the vapor cavitation erosion.