Investigation of flow over second generation controlled-diffusion blades in a linear cascade

• Main Author: Nicholls, Jennifer L.
• Other Authors: Hobson, Garth V..
• Language: en_US
• Published: Monterey, California: Naval Postgraduate School 2012
• Online Access: http://hdl.handle.net/10945/13711

Approved for public release, distribution unlimited. === This thesis contains a detailed investigation of second-generation controlled-diffusion compressor stator blades. The objective of the study was to compare the flow over and around the blades after the replacement of the tunnel motor, to that of previous studies. The inlet-flow angle was found to have increased from 39.5 deg to 40 deg with no movement of the blades in the tunnel. The blades were investigated at the new off-design inlet-flow angle using multiple experimental techniques. Surface flow visualization was used to view the overall blade surface flow characteristics. Blade surface pressure measurements were taken from an instrumented blade and the distributions of pressure coefficients were calculated. A pressure rake probe was used to confirm the inlet endwall boundary layer thicknesses. Five-hole probe wake surveys were performed to determine loss coefficients and axial velocity ratios. Two- component laser Doppler velocimetry (LDV) was used to characterize the flow in the inlet, in the wake and the suction-side boundary layers of the blades. Good correlation between techniques was found. The increased angle of incidence on the blades resulted in increased loading, and at the low Reynolds number, a smaller laminar separation bubble was observed.