Numerical and Experimental Investigation of Lasered Riblets on Turbine Exit Guide Vanes and the Impact on the Performance

The reduction of losses in a turbine exit casing (TEC) with lasered Riblet-surfaces is examined. So called Riblets are streamwise grooved surfaces which reduce the viscous drag in turbulent boundary layer. Since lasered Riblets have the advantage of being resistant to higher temperatures, new areas of application such as turbo machines have opened up. The Riblets were designed in a numerical way with a special algorithm. The change of flow due to Riblets is estimated with an unsteady CFD simulation. Based on the numerical design the Riblet-surface was lasered onto the suction side of the turbine exit guide vane (TEGV). Measurements were performed on a TEC with smooth TEGVs and one with riblet-TEGVs. Five-hole probe data shows a reduction in pressure loss of 7.2% in the area of the TEC.