Three-dimensional near wall flow phenomena of a tandem cascade

Authors

T. Frey, M. Böhle - TU Kaiserslautern, Germany

Abstract

The two dimensional flow in tandem cascades has often been performed in the open literature. The suggestion is that tandem blades may be superior to single blades, especially for large turning angles. For tandem cascades with a low aspect ratio the losses that are generated at the wall are very important. But up to now less information about the flow structure near the sidewall are available. Based on current numerical and experimental investigations, the present paper reports on the influence of a tandem cascade configuration on the wall induced losses in an axial compressor. The examinations are performed with a tandem cascade turning the flow from approximately 50° at a Reynolds number of Re_l = 8 *10⁵. The load split is 50%. The profiles are NACA65 with circular camber lines. It was designed using empirical correlations of Lieblein and Lei. One goal of the paper is to check the applicability of the criteria of Lei for tandem cascades which was originally developed for single cascades. Therefore the forward blade was designed so that corner stall occurs according to the criteria of Lei. As the numerical simulations show, the effect of corner stall is suppressed in the design point. The flow phenomena and the comparison of the losses from two-dimensional flow and three-dimensional flow shows, that the main losses of a tandem cascade are generated at the sidewall. The losses are dependent on the configuration of the blades.