INVESTIGATION OF AERODYNAMIC LOSSES AND FILM COOLING EFFECTIVENESS FOR A NGV PROFILE

Efficiency increase is one of the design targets of a gas turbine. In the highly cooled front stages the air injection out of film cooling holes and the mixing with the hot gases contributes to aerodynamic profile losses. Design parameters for film cooling rows, which the losses influence, are amongst others the blowing rate, the momentum ratio, the shape of the fan and the angle between cooling hole axis and airfoil surface. The film cooling effectiveness is depending on these parameters as well as from the choice of the locations of the film rows. Two series of tests were carried out for a nozzle guide vane at two different linear test facilities. One test series investigated the aerodynamic loss behaviour of the profile under two different cooling schemes, where the locations of cooling air injection on the airfoil suction side varied. Results show a significantly lower aerodynamic loss for the configuration with injection in the front region of the airfoil. In the second test series the film cooling effectiveness of a selected cooling row in the front region on suction side of the airfoil was measured. The analysis of the measurements show that the film is attached to the airfoil over the whole length up to the trailing edge and proved its operability under different flow regimes.