EXPERIMENTAL TESTS TO ESTIMATE THE AERODYNAMIC BEHAVIOUR OF TURBINE BLADES WITH VARIOUS SECONDARY AIR EXHAUST FOR COOLING AT TRAILING EDGE.

The first few rows of a modern gas turbine have to be cooled. Especially the trailing edge with high heat transfer coefficient requires effective cooling. This can be achieved either by convective or film cooling. The cooling air at the outlet causes mixing losses and extra edge loss due to the thick trailing edge necessary. Three different types of trailing edge configurations for the secondary air exhaust were experimentally tested in the cascade tunnel at the Institut fuer Flugantrieb, Technische Hochschule, Darmstadt (Western Germany). The purpose of the tests was to determine the change in aerodynamic behavior of these profiles due to secondary air. The change in flow ddeflection angle and loss coefficients were evaluated as a function of momentum ratio of secondary air to main stream.