A strategy is outlined on how to introduce two-phase flow correlations into air/oil system calculations for aero engines.

The importance of two-phase flow effects is highlighted by demonstrating their particular significance for the high altitude performance of a vent system.

For air/oil mixtures very little can be obtained from the literature and correlations derived from air/water test results have to be corrected. For critical flow conditions in restrictors an improved method is developed. Some test data obtained for air/oil mixtures show, that the proposed correlations agree fairly well.

Furthermore, it is shown how numerical methods for this complex field of fluid dynamics can be used in the future by the example of phase demixing by centrifugal forces.

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