An evaluation strategy of control method for corner separation/stall in compressor cascades

Abstract

The modern design of turbomachinery tends to use a combination of the sweep, dihedral and endwall treatment methods to prevent the corner flow from separating. However, there are few rules for selecting the most effective endwall treatment methods and evaluating their efficiencies. In this paper, an evaluation method for the two phenomena that affect the endwall flow field is presented based on the diffusion parameter DJ. The method contains two models: the first is for the phenomenon of the boundary layer intersection in the corner (B), and the second is for the endwall secondary cross flow (E). The BE rule is presented by taking both B and E into account. The corner stall occurs when $B·E>1$, and the value of B and E can be used to evaluate the severity of the two flow phenomena. The control efficiencies of the four kinds of endwall treatment methods are compared with one another using the BE rules. The four kinds of endwall treatment methods are end dihedral, blended blade and endwall, endwall grooves, and endwall vortex generators. The severity of the endwall secondary cross flow in the test case is more serious than the severity of the boundary layer intersection. The numerical results show that the control efficiency of the end dihedral, blended blade and endwall, endwall grooves, and endwall vortex generators are 23%, 50%, 34.6%, and 67.3%, respectively.