Numerical analysis of two-phase flow and separation efficiency in a dynamic pressure oil-air separator for aero-engines

The dynamic pressure oil-air separator plays a vital role in aero-engine lubrication systems, as its performance directly determines overall reliability and efficiency. To enhance lubrication performance, it is essential to understand the internal flow characteristics within the separator. In this study, a Mixture multiphase flow model was employed to numerically investigate the oil-air two-phase flow field inside the separator. The effects of inlet velocity and initial oil-air ratio on the distributions of air phase, tangential velocity, and axial velocity were systematically analyzed to elucidate the correlation between flow field structure and separation performance. Numerical results indicate that the tangential velocity distribution conforms to a Rankine vortex structure: a forced vortex exists in the central region, while a free vortex forms near the wall. Axial velocity is negative near the central axis, indicating air motion toward the outlet, and positive near the wall, representing oil motion toward the bottom. At an initial oil-air ratio of 7:3, increasing the inlet velocity from 3.5 to 4.5 m/s stabilizes the internal swirling flow and mitigates air accumulation at the bottom, raising separation efficiency from 90.7% to a maximum of 93.9%. Moreover, a higher initial oil-air ratio facilitates a stable, continuous oil film along the wall, suppressing turbulent interphase mixing. Consequently, at 4.0 m/s, increasing the ratio from 7:3 to 8:2 further enhances efficiency from 92.5% to 93.3%. Numerical predictions agree well with experimental data, with a maximum error of 6%.