Film Cooling Effectiveness in the Showerhead Region of a Gas Turbine Vane: Part II — Stagnation Region and Near-Suction Side

Abstract

An experimental study was conducted to determine the effects of film cooling on a gas turbine vane at two mainstream turbulence intensities of Tu = 0.5% and Tu = 22%. The low speed turbine vane test facility was designed to match the Reynolds number of operating engine conditions. The nine-time scale model airfoil simulates a gas turbine first-stage stator vane. The leading edge film cooling hole showerhead array included six rows of film cooling holes configured with one stagnation row, two pressure side rows, and three suction side rows. This paper presents film cooling effectiveness measurements in the stagnation region and near-suction side. Cooled air injection was used to conduct the tests at a density ratio of DR = 1.8 and blowing conditions over a range of M = 0.5 to M = 2.9. Infrared imaging techniques were used to measure the surface temperature distribution. The results provide a detailed evaluation of the effects of blowing ratio, mainstream turbulence, and stagnation line position on the measured effectiveness in the showerhead. The effect of increasing blowing ratio generally resulted in increased spanwise averaged effectiveness levels. The effect of mainstream turbulence varies with blowing ratio within the showerhead region. At low blowing ratio, high turbulence produced greater effectiveness, whereas at high blowing ratio, low turbulence produced greater effectiveness. The effect of stagnation line position also varied with blowing ratio. Overall, the dominating effect occurred when the blowing ratio was sufficiently strong to cause a spanwise merging of adjacent cooling jets resulting in very good spanwise uniformity and high adiabatic effectiveness.