ABSTRACT
The continuing effort to predict off-design performance and stalling behavior of compressor blades during the design phase has prompted studies to characterize the flow in and around leading-edge separation bubbles of blades in cascade. One of the earliest studies of stall in a two-dimensional cascade was performed by Emmons et al. (1955), who presented propagating stall observations in a cascade. They presented qualitative flow, viz., pictures, to complement the measurements performed in actual compressors. They also performed simultaneous hotwire measurements upstream and downstream of the cascade and were able to tabulate, for instance, the fraction of time that the airfoils were at stall for various flow speeds. Another excellent paper on compressor stall was presented by Sovran (1959). He obtained measurements and used smoke flow visualization to study rotating stall in an axial-flow compressor and in a cascade of seven blades. He also produced a movie of the stalling process in the cascade for low Reynolds number flow. More recently, Yocum and O’Brien (1993) presented flow visualization and time-mean velocity measurements of 328stalled flow in a cascade. They also presented a good historical perspective of earlier cascade studies as an introduction to their measurements. Experimental studies have attempted to map viscous flow development in specific geometries. Recently, Hobson and Shreeve (1993) reported detailed two-component laser-Doppler-velocimetry (LDV) measurements of the flow through the same set of controlled-diffusion (CD) compressor blades in cascade at a high incidence angle prior to stall.
