AN EXPERIMENTAL INVESTIGATION OF AN IMPROVED FILM-COOLING CONFIGURATION AT A TURBINE VANE ENDWALL TO REDUCE THE AMOUNT OF COOLANT

Kurzfassung

In the Windtunnel for Straight Cascades (EGG) at DLR, Goettingen, thermodynamic investigations were performed applying an improved cooling scheme to establish film cooling at the endwall of a first stage stator. Based on the results from an earlier project the slot position in front of the cascade, as well as the number and the arrangement of the cooling holes within the passage were improved to reduce the necessary amount of coolant. The experiments were carried out at an exit Mach number of 1.0 and at a downstream Reynolds number of 850,000. An infrared camera was used to collect the thermal data of the homogeneous heated endwall, which was appended with electric operated heating foils. The temperature of the coolant flow was adjustable which was necessary for the use of the superposition method. Therefore, the values for heat transfer coefficients and film cooling effectiveness were obtained under similar boundary conditions.

The experiments proved the progress in coolant management achieved when applying the new improved cooling configuration instead of the previous one. The slot coolant mass flow rate was more than halved without reducing the film cooling effectiveness. The holes rearranged within the passage close to the pressure side significantly improve platform cooling at a reduced demand of coolant, too.