Vibration analysis of journal bearings under the contaminated lubricating oil with solid particulates
Abstract
Journal bearings are widely used in important machines such as engines, turbine generators, pumps etc. While in operation, the applied load is supported as a result of the hydrodynamic force generated by the lubricating oil flowing through a convergent oil wedge. Due to the small clearance, a pure and clean lubricating oil must be guaranteed. Due to various reasons lubricating oil can be contaminated to have micro-particles, lead to fast wear and shorten bearing life, and even cause secondary damages to bearing-rotor systems. Solid particulates, as one of the common contaminants, in the lubricating oil, will have a significant impact on the lubrication characteristics. With a certain concentration being reached, the micropolar fluids that represent fluids consisting of rigid, randomly oriented particles suspended in a viscous medium will be formed, and thus the lubricating oil will no longer perform the Newtonian fluids behaviour. This rheological behaviour will then inevitably affect the dynamic performance of rotor bearing system. It would therefore be meaningful to establish the relationship between the dynamic performance of the journal bearing and the concentration of solid particulates in the lubricating oil. In this paper, the research progress regarding the effects of solid particulates on the lubrication characteristics is firstly reviewed in the introduction. A theoretical model is then developed for the dynamic coefficients of the journal bearing under such contaminated lubricating oil based on the micropolar fluids theory. Especially, it take into account the influence of shear rate and temperature on the viscosity of the lubricating oil by different concentration of solid particulates The shaft locus and the housing vibration are then experimentally studied. This research paves ways for vibration based online monitoring of journal bearing performances.
