An experimental study of three-dimensional high-speed air conditions in a cascade of axial-flow compressor blades

Abstract

Detailed investigations have been made by optical and physical methods in a high-speed wind tunnel of the flow characteristics of two compressor blade cascades. In Part 1 a representative high-camber cascade was examined at zero incidence over entry air velocities ranging from low to critical. Traverses were made of discharge angles and wake losses at all heights so that a relation between two and three-dimensional losses could be obtained. Some records were also made of the nature of the vortices induced in the discharge flow. In Part 2 the blade and passage designwas conditioned by the findings of Part 1, with the aim of so modifying the cascade that its efficiency in the critical flow region would be improved. Optical and physical examinations were again carried out over a range of both incidence and velocity. The results from Part 1 indicate that although fully developed shock formations can be used to bring about reduction in profile drag, the net performance of a conventional cascade is prohibitively low when shock occurs, by reason of the shock losses themselves. The results from Part 2 show that by delaying the advent of shock, and by reducing its intensity and complexity, an improvement in high-speed performance can be achieved, although at a somewhat limited incidence range.