Numerical Study on the Effects of Dihedral Stators in a Transonic Axial Compressor

This paper presents the effect of dihedral stators on flow behavior in a transonic axial compressor. A commercial flow solver was used to calculate the performance and flow characteristics of a transonic axial compressor with different shapes of stators modified by changing the shape of the stacking line. In a stator with a straight stacking line, large corner separation occurred between the suction surface and the shroud endwall and caused a large total pressure loss under high loading. In this study, the dihedral stator induced a significant pressure loss on the blade at the peak efficiency point owing to the increased corner separation area. The shroud dihedral generated a radial pressure gradient and caused a low-momentum flow to migrate from the shroud endwall toward the midspan, consequently decreasing the diffusion factor near the shroud endwall. Although the hub dihedral generates unexpected hub-corner separation causing a large total pressure loss over the entire operating range, the loss region makes the high-momentum flow near the hub divert toward the upper part of the passage. Therefore, the amplitude of the low-frequency term according to the shroud-corner separation also decreased, and the stall limit of the compressor was improved with the hub dihedral stator.