A Numerical Design Space Investigation of Low-Speed Axial Compressor Stages Using Single-Row and Tandem Bladings

Abstract

Abstract Past studies have demonstrated that tandem aerofoil configurations in modern axial compressors enhance efficiency and reduce weight by leveraging increased loading capabilities from a more stable boundary layer around the rear aerofoil. However, higher loadings and the introduction of a second aerofoil introduce a more complex secondary flow field, which may compromise the efficiency and working range of the tandem aerofoil configuration. This work aims to deepen the insights into favoring tandem configurations. While conventional single aerofoil behavior is well-established in a condensed Smith-chart (work coefficient vs. flow coefficient), indicating optimal regions, a comprehensive Smith Chart for tandem aerofoils is absent and their peak efficiency design point location remains uncertain. The study follows the S1-S2 design approach, accounting only partially for secondary flow effects due to its quasi-3D nature. This serves as a foundation for a more detailed 3D analysis. The studys baseline utilizes the 3.5 stage axial research compressor at the Institute of Turbomachinery and Flight Propulsion (TUM), focusing on redesigning the first 1.5 stages. Configurations include IGV, single rotor-stator, or tandem rotor-stator setups. Numerical analyses rely on the MTFLOW throughflow solver from MIT and 2D steady state RANS simulations using TRACE (DLR) for blade-to-blade evaluations. The findings of this paper will allow future designers to narrow down the ideal design space of tandem aerofoil configurations in axial compressor stages and to predetermine the benefits of tandem vs single aerofoil configurations, depending on their design conditions.