Adiabatic effectiveness measurements in a first stage nozzle cascade having endwall contouring, leakage and assembly features

The first stage vane section of a modern gas turbine engine is assembled with a gap between the combustor and the vane platform and a second gap on the platform. To prevent ingression, leakage flow is provided through each gap. In this paper, the effectiveness of the leakage flow as an endwall film coolant is measured. The cascade geometry includes axial contouring of the cooled endwall and several step configurations for each gap. The steps reflect assembly or differential thermal growth misalignment. Various blowing rates are applied through each gap to allow assessment of the changes in effectiveness with changes in leakage rate. Thus, the results presented herein show how the gaps, steps, and leakage rates alter the cooling effectiveness of the leakage flow. Shown are some cases where steps improve the film cooling effectiveness. In other cases, enhanced mixing due to gaps, steps, or increased leakage reduces effectiveness.