Abstract: The oil lubricating hydrodynamic journal bearing is an important load-bearing component of the large rotating machinery. In its clearance, the hydrodynamic-pressured and cavitation effect coexist, forming the gas-liquid two phase flow, the characteristics of which affect both the bearing performance and safety operation of the equipment. The influence of non-condensable gas(NCG) contend in lubricating oil is investigated. It is considered that NCG can cause the oil to deviate from its nominal performance and involve in the gas-liquid mass transfer process. The coupling relationship between hydrodynamic-pressured and cavitation effect based on the flow feature in bearing clearance is present; moreover, a 3D flow field simulation model using the two phase flow theory of computational fluid dynamics(CFD) is set up. The full cavitation model and gas-liquid mixture model are applied in the approach. It is concluded that the flow characteristic trend is piecewise, a certain series of features applying to a certain interval of the NCG’s domain. The characteristic of the flow, such as the max pressure, the max gas contend and the bearing load force, tend to be non-monotone with the change of NCG contend, there is a peak interval. Calculation results also show that the migration of the pressure field distribution area, and phase field distribution occur with the NCG variation.

Key words: gas-liquid two phase flow, journal bearing, non-condensable gas