Aerodynamic Design and Evaluation of a Low-Speed Axial Compressor Rotor via High-to-Low-Speed Scaling

Low-speed compressors are widely used to investigate the aerodynamic behaviour of real engine axial compressors because they enable detailed flow measurements at lower cost and reduce experimental complexity. However, compromises in similarity parameters during scaling may affect the reproduction of three-dimensional tip-region flow structures. In this paper, a low-speed axial compressor rotor is designed from a high-speed (HS) reference rotor; NASA Rotor 37 operating at 60% design speed using an inverse design approach. The aim of the inverse design method is to find a rotor profile that matches the target blade loading distribution based on the NASA Rotor 37. Three-dimensional RANS numerical simulations are performed to evaluate aerodynamic performance, surface pressure loading (Cp) and the spanwise stage loading coefficient distribution (ψ) at near-design operating conditions between the HS and low-speed (LS) rotors. The LS rotor successfully reproduces the target stage loading coefficient distribution of the reference HS rotor. The total pressure losses are evaluated for both LS and HS rotors at the location aft of the rotor trailing edge. Quantitatively, both rotors show about four times growth in losses in the tip region when comparing between near-design and near-stall conditions. In the passage region (0.1 < span < 0.8), losses increase approximately two-fold near stall for both rotors compared to near-design conditions. Conversely, hub region pressure losses of both LS and HS rotors show a slight decrease under near-stall conditions compared to near-design conditions. Overall, the re-scaling methodology is satisfactory because the LS rotor matches the target mid-span stage loading coefficient within 0.5% and preserves surface pressure distributions (Cp) despite unavoidable similarity compromises in tip clearance and flow coefficient.