Incidence Effects on Aerodynamic and Thermal Performance of a Film-Cooled Gas Turbine Nozzle Guide Vane

In this study, the influence of inlet flow incidence on the aerodynamic and thermal performance of a film cooled linear nozzle vane cascade is fully assessed. Tests have been carried out on a solid and a cooled cascade. In the cooled cascade, coolant is ejected at the end wall through a slot located upstream of the leading edge plane. Moreover, a vane showerhead cooling system is also realized through 4 rows of cylindrical holes. The cascade was tested at a high inlet turbulence intensity level (Tu1 = 9%) and at a constant inlet Mach number of 0.12 and nominal cooling condition, varying the inlet flow angle. In addition to the reference incidence angle (0°), four other cases were investigated: +20°, +10°, -10° and -20°. The aero-thermal characterization of vane platform was obtained through 5-hole probe, endwall and vane showerhead adiabatic film cooling effectiveness measurements. Vane load distributions and surface flow visualizations supported the discussion of the results. On the vane, a significant movement in stagnation point happened when incidence angle varied, resulted in changing of the coolant distribution pattern between SS and PS of the cooled vane; which adversely affects the efficiency for both negative and positive inlet flow incidence angles. On the platform, however, a relevant negative impact of positive inlet flow incidence on the cooled cascade aerodynamic and endwall thermal performance was detected. A negligible influence was instead observed at negative incidence, even at the lowest tested value of -20°.