Effects of end-walls on flows in a highly loaded compressor cascade with double-circular-arc blades
A numerical study is carried out to understand the flows in a highly loaded compressor cascade made of double-circular-arc blades, which were measured by Zierke and Deutsch in the late 1980s. A two-dimensional (2D) cascade with periodic boundary conditions in both pitch-wise and span-wise directions and a three-dimensional (3D) cascade with two end-walls that are far away from each other are accounted for in the study. For the incidence angle α = - 8.5 °, the numerical results of the 2D-cascade flow are in excellent accordance with the experimental data. This not only validates the numerical method used in the study but also suggests that a 2D and periodic flow was successfully generated in the experiment for this incidence angle. However, the numerical results of 2D-cascade flows for α = - 1.5 ° and 5 ° deviate from the experiment considerably because the strong effects of the end-walls on the wake are neglected in the simulation. By contrast, the simulation of 3D-cascade flows predicts an accurate pressure coefficient at the blade surface, the pressure increase coefficient, and the total pressure loss coefficient for all three incidence angles. This means that, to generate experimental data for validating numerical simulation, it is important to consider the effect of end-walls when the incidence angle is large. The numerical results also show that, for 2D-cascade flows with a low inlet turbulence intensity, the laminar-turbulent transition on the pressure surface is determined by the interaction of the Klebanoff distortions and T-S waves. The Klebanoff distortions are also clearly identified on the suction surface for α = - 8.5 °. The end-walls induce span-wise elongated disturbances, which suppress the stream-wise disturbances. The transition in 3D-cascade flows generally follows the mechanism of natural transition.
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The authors gratefully acknowledge the support of this study by the DFG-Heisenberg program (299562371), the grant of the National Natural Science Foundation of China (No. 51922098). The calculations were carried out at the Computing Center of Hamburg University of Technology (RZ-TUHH) and the North-German Supercomputing Alliance (HLRN).Acknowledgement is also given to Mr. Es Sbai of University of Oldenburg for his contribution to the computational mesh.