Flow Dynamics of a Subsonic Axial Compressor Rotor With Leaned Tandem Blades

Abstract For higher diffusion, tandem blading has demonstrated performance superiority over a conventional blade. Modern compressor blades are often designed with three-dimensional blade shapes such as sweep, lean, dihedral, end bent etc., to achieve optimum performance. However, the performance benefit reported due to the three-dimensional blade shapes have been design-specific. Since a tandem rotor involves an unconventional design approach, each aspect of the 3D blade design needs to be looked at separately. The present numerical study aims to investigate the performance of a tandem rotor with lean. The performance of the leaned tandem rotor is also compared with the conventional leaned rotor. Positively leaned tandem configurations exhibited a higher total pressure rise than the other configurations, but at the expense of the operating range. On the other hand, a significant improvement in the operating range is observed for the negatively leaned tandem rotor. This, however, comes with a total pressure penalty. For the negatively leaned tandem rotor, a higher mass flow migration towards the tip region is observed. This reduces the effective incidence of the rotor tip. Therefore, a higher stall margin is observed for the negatively leaned tandem rotor. However, a higher tip incidence angle for the +20° leaned tandem rotor results in an early breakdown of the forward rotor tip leakage vortex, resulting in a lower stall margin. Although incorporating lean within the design of conventional rotor has certain performance benefits, it appears to be more beneficial for the tip sensitive tandem rotor design.