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

Abstract

Fluid dynamic of axial compressor blades under different surface roughness levels is experimentally investigated in this research work. An open circuit wind tunnel has been prepared for the test model of a linear cascade of axial compressor blades. Reynolds number ranged between 100000 and 300000 and free turbulence intensity was 2%. Four different roughness levels, ranged between\(10.96 \text{a}\text{n}\text{d} 68.54\mu m\) besides smooth surface case were examined. Hot wire anemometry has been undertaken to extract velocity profiles to distinguish boundary layer type in terms of laminar, transitional or turbulent regimes, and also to investigate occurring laminar separation bubble. Total pressure loss coefficient was also calculated for different Reynolds numbers and surface roughness levels. The results showed that the boundary layer remains in fully laminar regime for flows with Reynolds numbers less than about 150000 for smooth surface case. At the lowest test Reynolds number adding surface roughness caused the total pressure loss to decrease. Highest Reynolds number was accompanied by the lowest losses for the smooth surface. Increasing the surface roughness caused losses to increase at this Reynolds number. Furthermore, roughening the surface caused the bubble to shrink, and transition point to shift upstream accompanied by reduction in pressure loss.