Experimental Investigations of Surface Roughness Effects on Aerodynamic Performance of Axial Compressor Blades

This study experimentally investigates the aerodynamic behavior of axial compressor blades under different surface roughness conditions. An open-circuit blowing-type wind tunnel was modified to conduct tests on a linear cascade of compressor blades. The experiments covered a Reynolds number range of 100,000 to 300,000 with a freestream turbulence intensity of 2%. Four surface roughness levels were tested in addition to a smooth reference blade. Hot-wire anemometry was employed to measure velocity profiles at several chordwise stations and to identifying the flow regimes as laminar, transitional or turbulent. The hot-wire surveys also helped detect the possible formation of laminar separation bubbles. Total pressure loss coefficients were measured for various Reynolds numbers and roughness levels. The results indicate that for smooth blades, the boundary layer remains fully laminar at Reynolds numbers below approximately 150000. At the lowest Reynolds number, introducing surface roughness reduced the total pressure loss, whereas at higher Reynolds numbers, roughness increased the losses and the smooth surface performed better. Surface roughness was found to suppress or shrink the laminar separation bubble and shift the transition onset upstream. Overall, the findings demonstrate how both the Reynolds number and surface finish quality affect flow regimes and aerodynamic losses. The present work provides quantitative data linking roughness parameters to aerodynamic performance, offering valuable insights for blade design optimization under different operating conditions.