Film-cooling flowfields with trenched holes on an endwall

The leading edge region along the endwall of a stator vane experiences high heat transfer rates resulting from the formation of horseshoe vortices. Typical gas turbine endwall designs include a leakage slot at the combustor-turbine interface as well as film-cooling holes. Past studies have documented the formation of a horseshoe vortex at the leading edge of a vane, but few studies have documented the flowfield in the presence of an interface slot and film-cooling jets. In this paper, a series of flowfield measurements are evaluated at the leading edge with configurations including: a baseline with neither film-cooling holes nor an upstream slot, a row of film-cooling holes and an interface slot, and a row of film-cooling holes in a trench and an interface slot. The results indicated the formation of a second vortex present for the case with film-cooling holes and a slot relative to the baseline study. In addition, turbulence intensity levels as high as 50% were measured at the leading edge with film-cooling holes and a slot compared to the 30% measured for the baseline study. A trench was shown to provide improved overall cooling relative to the no trench configuration as more of the coolant stayed attached to the endwall surface with the trench.