Flow Through Cascades of Slotted Compressor Blades

Abstract

The performance of axial flow compressors can be improved when it becomes possible to achieve higher loading per stage than currently attainable. The major obstacles to attaining this objective are the limitations on loading in the end wall region and the limited range of operating incidence of compressor blades. A possible method of achieving a wide range of operating incidence is the use of slotted or multibody airfoils. An incompressible, two-dimensional, potential flow analysis for thick, highly cambered multibodies in cascade is presented. The analysis is extended to include compressibility. A boundary-layer calculation, including a wake model, is described and used to predict cascade losses. Theoretical predictions are compared against slotted and unslotted cascade and compressor stator experimental results and adequate agreement obtained. The slotted blade concept is shown to offer performance benefits, provided that end-wall loading limitations can be overcome.