Boundary Layer Studies on Highly Loaded Cascades using Heated Thin Films and a Traversing Probe

In the continuing quest for increased turbine efficiency, the part played by blade profile shape remains crucial. Three turbine vanes with successively increased aerodynamic loading were tested in the High Speed Cascade Wind Tunnel at DFVLR Braunschweig. In addition to wake traverses, measurements of the boundary layer behavior were made. These consisted of (1) use of a constant temperature anemometer to measure the fluctuating heat transfer rate on an array of thin film platinum thermometers deposited on the vanes and (2) a flattened, traversing pitot probe held against the vane surface. Transition measurement by these techniques is described.