INFLUENCE OF THERMAL BARRIER COATING ROUGHNESS ON THE BOUNDARY LAYER STATE OF A HIGH-PRESSURE TURBINE VANE WITH HIGH ACCELERATION CLOSE TO RELAMINARIZATION

Abstract

This paper addresses how an engine relevant 7YSZ-thermal barrier coating (TBC) influences the boundary layer due to roughness. Experimental investigations on a NGV at the wind tunnel for straight cascades Göttingen (EGG) are conducted. The vane is modified so that the shape is not influenced by the thickness of the TBC. The roughness is expected to influence the location of the separation and transition. The effects that are influencing the transition next to the roughness are a positive and negative pressure gradient, separation and interacting shocks. The influence of the TBC will be discussed on the appearance of turbulent wedges, the position and the length of the separation bubble as well as the transition location. Together with previous investigations, this study creates a comprehensive picture of the aerothermodynamics of a turbine vane. Unsteady flow phenomena on a TBC coated NGV are investigated using ultra-fast-response temperature sensitive paint (iTSP). This data set will be used as a benchmark for innovative future turbine vane designs including TBC and extensive cooling. Additionally, the results will be used as a validation data set for numerical models and their improvement.