Numerical investigation of the influence of sweep and lean on a transonic axial compressor rotor

Abstract

The state-of-the-art gas turbine engine technology tends to have modules with superior loadings within the compact design strategy. The technology trend created a necessity to design transonic high-pressure compressors that are efficient while having a reasonably high operational range. Transonic regime creates additional design aspects that need to be carefully done, mainly shock related structures and losses. An efficient way to control shock structure is three-dimensional stacking, namely sweep and lean, which has been used for aircraft wing designs. The recent studies relevant to the three-dimensional stacking of compressor blades have not completely enlightened the flow mechanism behind the sweep and lean, which keeps the controversy about the sweep and lean alive. This paper aims to investigate the influence of three-dimensional stacking, namely true sweep and lean, on a transonic axial compressor stage with a 3D Reynolds Averaged Navier-Stokes solver. NASA Rotor 37, which is a common benchmark case used for numerical studies in the literature, is used for validation and further investigation study. A total of 8 new geometries based on NASA Rotor 37 have been generated that are swept and leaned with different characteristics. The generated geometries have been investigated with the validated numerical approach in terms of the flow field in a systematic way. The results show that the axially aft sweep and positive lean design improve the design point in terms of isentropic efficiency and stall margin. The mechanism behind the improvement is seen to be the relocation of the passage shock and the weakening of the tip leakage vortex. The outstanding cases among the offered geometries in terms of efficiency and the operational range are combined and investigated through a similar systematical approach. It is seen that the combined geometry has a 4.67% stall margin improvement and 0.83% isentropic efficiency improvement. It is noted that the improvement of the global performance parameters of combined geometry is higher than in singular cases however it is not the direct superposition of singular geometries' characters.