Design and performance analysis of a two-stage transonic low-reaction counter-rotating aspirated fan/compressor with inlet counter-swirl

This paper presents detailed aerodynamic designs of the two-stage high-load fan/compressor, including a conventional high-reaction fan/compressor (HRC) and a low-reaction aspirated counter-rotating one (LRACRC) with inlet counter-swirl and a comparison of critical performance parameters. With an organic integration of four high-load design methods involving low reaction, aspiration, counter-rotation and inlet counter-swirl into the design system, LRACRC enables a peak total pressure ratio of approximately 6 and a peak through-flow efficiency of 88%, respectively, at a tip speed of 370 m/s and 378 m/s for two rotors and an overall aspiration flow fraction of 22.25% inlet mass flow. Compared with HRC, LRACRC attains a performance improvement, which is 129.46% higher in peak total pressure ratio and 1.55% higher in peak efficiency, respectively. The loading coefficient of the two rotors is dramatically enhanced from 0.36/0.36 in HRC to 0.70/0.88 in LRACRC. CFD analysis reveals that there is no large-scale separation for LRACRC at peak efficiency condition but the excessive bleed flow causes a small-scale separation on the pressure side of the adjacent blade. Besides, the large tip clearance of the second rotor induces a strong tip leakage, leading to a remarkable drop in efficiency of the second stage from LRACRC. The current design study fills the gap of the ultra-high-load supersonic/transonic fan/compressor with a comprehensive utilization of low-reaction design method, aspiration, counter-rotation and inlet counter-swirl and the available design space is further expanded.