Effects of surface roughness on heat transfer to gas turbine blades

A brief, preliminary sample of results of an investigation into the effect of surface roughness on heat transfer to gas turbine blades is presented. Only the kind of roughness due to the accretion of dirt or dust is considered and this has been simulated in cascade flow by attaching various grades of abrasive powders to the blade surface with a water soluble adhesive. A significant increase in heat is reported particularly with high free stream turbulent levels. Roughness on the pressure surface alone is shown to increase the overall heat transfer without any corresponding increase in profile loss.