Measurements and computations of roughness effects on performance of a HP turbine cascade in compressible flow

Experimental and numerical studies have been conducted to investigate surface roughness effects on aerodynamic performance of a high-pressure (HP) turbine cascade with compressible flow. This work continues earlier work at Carleton University on roughness effects on performance of a large-scale turbine cascade with incompressible flow.; The experiments were conducted in the Carleton University High Speed Wind Tunnel. The surface roughness consisted of randomly distributed sand gains adhered to the suction surface of the blades. The roughness height, the width of the roughness band and the band location relative to the leading edge were varied. The profile loss coefficient and exit flow deviation angle were determined from wake traverse measurements. The tests were run for exit Mach numbers ranging from 0.40 to 1.13, corresponding to exit Reynolds number, based on true chord and exit flow velocity, ranging from 4.0 x 10 5 to 10 x 106.; Roughness on the suction surface produces large increases in profile losses, but has little effect on the exit flow deviation angle and blade pressure distribution or loading. The losses are strongly influenced by the roughness height and by location of the roughness band relative to the leading edge. Mach number is found to have an important effect on the magnitude of the losses.; The FLUENT code was employed for the numerical computations. The Spalart-Allmaras turbulence model with wall functions was used for smooth and roughened blades. The predicted trends for profile loss coefficient and exit flow deviation angle for roughened blades were essentially the same as the experimental trends. The agreement between predicted and experimental results is fairly good.