Inlet Turbulence Distortion and Viscous Flow Development in a Controlled-Diffusion Compressor Cascade at Very High Incidence

Abstract

Detailed two-component laser Doppler velocimeter (LDV) measurements of the flow through a controlled-diffusion (CD) compressor cascade at a Reynolds number of about 700,000 and at a low Mach number are reported in this article. A very high-incidence angle (8 deg above design) was considered throughout this investigation, which included the full experimental characterization of the turbulence Held. The LDV measurements were fully automated and were all taken in coincidence mode, thus turbulent flow correlations could be determined. Most significant was the measurement of the distortion of the inlet freestream turbulence upstream of the blade leading edges. Such information is important in assessing viscous codes which incorporate transport equations to describe the turbulence within the flowfield. The laminar leading-edge separation bubble, which reattached turbulent, was enlarged on the suction surface of the blade. Consistent with measurements at lower incidence angles, the suction surface boundary layer remained attached over the rear part of the blade. The pressure side boundary layer initially showed little or no growth, however, it finally developed into a profile similar to a wall jet. The wake profiles showed significant asymmetry due to the high loading on the blades at the increased incidence angle.