The paper discusses an approach to predict the two-phase flow regime in an aero engine bearing chamber. In general, one of two distinct flow regimes can occur in a bearing chamber. At lower shaft speeds, the oil flow is only partially affected by the air flow, which is driven by the rotating shaft. At higher shaft speeds, however, the rotating air flow forces the oil film at the chamber walls to rotate, too. Thus, the two flow regimes correspond to two very different oil film distributions inside a bearing chamber presumably with significant consequences for the internal wall heat transfer. In order to determine the driving parameters for the flow regimes and the change between them, experiments were carried out with a bearing chamber test rig. With this test rig all relevant operating parameters as well as the geometry of the bearing chamber could be varied independently. The analysis of the experimental data allowed defining a general parameter which takes into account the chamber pressure, shaft speed, oil viscosity and chamber length. The influence of the oil flow rate and the overall dimensions are assessed qualitatively.
