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

An experimental program to study film cooling adiabatic effectiveness in the showerhead region of a turbine vane was completed. A typical first stage turbine stator vane was modeled in a nine-times scale, low speed test facility. The leading edge showerhead consisted of a row of holes at the stagnation point of the vane as well as two rows on the pressure surface and three rows on the suction surface. Film cooling performance on the pressure side of the showerhead is described in this paper. Experiments were conducted for a number of blowing ratios, from 0.3 to 2.9, and at a density ratio of nominally 1.8. The impact of high mainstream turbulence was studied by comparing performance at turbulence levels of 0.5% and 22%. The sensitivity to the stagnation line position was also investigated. The approaching stagnation line was positioned either directly on the stagnation row of holes or just to the suction side of that row. With the stagnation line directly on the stagnation row of holes at low turbulence, the direction of the coolant jets was observed to vary along the span of the airfoil. At high turbulence, this same effect did not occur. Moreover, at the high mainstream turbulence level, the coolant from the entire stagnation row of holes seemed to be spread more evenly throughout the stagnation region. At high blowing ratios, this resulted in higher effectiveness values in the stagnation region. Farther downstream, the high mainstream turbulence reduced the effectiveness at all blowing ratios.