Film cooling experiments with flow introduced upstream of a first stage nozzle guide vane through slots of various geometries

This paper describes the advantages of introducing film cooling flow through the endwall upstream of the first stage nozzle guide vane. To perform these studies, a linear cascade is built. It consists of three vanes and two endwalls that form two passages. One endwall is flat and the other is contoured from upstream of the leading edge, continuing through the passage. The approach flow is of high turbulence and large length scale, representative of the engine combustor exit flow. Film cooling flow is introduced through two successive rows of slots, a single row of slots and slots that have particular area distributions in the pitchwise direction. Measurements are taken by heating the film cooling flow slightly above the main flow temperature and recording temperature distributions in the film cooling flow-main flow mixing zone at various axial planes. The single and double slot injection cases represent base-line injection geometries. They show that at lower ratios of coolant to main flow momentum fluxes, film cooling flow migrates toward the suction side due to secondary flow. At higher ratios, the pressure side endwall region is cooled more effectively. Observations are drawn by comparing the baseline injection cases with cases of different geometries for which slots are blocked partially to re-distribute mass and momentum injection rates of the emerging flow. The downstream evolutions of temperature contours are discussed. The idea is to utilize secondary flows to control pitchwise coolant distributions.