Experiment and prediction model of windage losses in rear drum cavity in secondary air system of aero-engine

The increasing overall pressure ratio of aero-engines has led to considerable windage losses in the Rear Drum Cavity (RDC) of the secondary air system. These losses convert turbine power into thermal energy, resulting in both energy consumption and a reduction in the rotor's operational lifetime. To expand the experimental database to engine-representative non-dimensional conditions, a comprehensive experimental study was conducted, with the mass flow coefficient C_w ranging from 3.54 × 10⁴ to 7.59 × 10⁴ and the rotational Reynolds number Re_ϕ ranging from 3.31 × 10⁶ to 1.02 × 10⁷. The effects of C_w and Re_ϕ on windage characteristics and swirl ratio distribution are analyzed. Furthermore, a theoretical model incorporating core swirl ratio modification and an empirical model are derived to predict windage losses. The experimental results indicate that windage losses are intensified by increasing C_w and Re_ϕ, leading to a maximum power consumption of 8 kW and a temperature rise of 54.6 K. Significant windage losses are predominantly driven by a weakened swirl ratio, which arises from the disturbance induced by the stator-mounted bolts. Particularly in the rear region of the RDC, the swirl ratio declines monotonically along the radial direction, showing minimal variation across all operating conditions, while the core swirl ratio remains consistently low, at approximately 0.2. Compared to the experimental data, the theoretical model exhibits an average error of 11% and the empirical model achieves a lower average error of 3%. These findings hold significant implications for enhancing the performance analysis of aero-engines.