| To develop quality computational codes for the film cooling of a turbine vane, a detailed understanding is needed of the physical mechanisms involved during the mainstream-coolant interaction. The majority of data in the open literature uses the adiabatic effectiveness and the heat transfer coefficient as defining measures of this interaction. However, these measurements only provide a footprint of data. To encapsulate the effects of the mainstream-coolant interaction on the thermal and velocity field, "off-the-wall" techniques are needed. This study addresses these "off-the-wall" measurements using flow visualization, thermal profiles, and laser Doppler velocimetry measurements to define the thermal and velocity field. This study focused on the film cooling performance within the showerhead and pressure side region of a turbine vane. The showerhead consisted of six rows of spanwise oriented coolant holes, d = 4.11mm, with a 25° injection angle. This spanwise orientation was directed away from the top and bottom endwall creating a region of opposing coolant jets. The pressure side film cooling consisted of a single row of holes oriented with a 30° injection angle and a 45° streamwise angle located 25d downstream of the stagnation line. The "off-the-wall" techniques were performed at DR = 1.2 and the adiabatic effectiveness tests performed at DR = 1.8. An examination of the effects of this varying density ratio on the adiabatic effectiveness was performed to allow for the proper scaling of the "off-the-wall" data. The film cooling was subjected to low mainstream turbulence, Tu infinity = 0.5%, and two levels of high mainstream turbulence, Tu infinity = 7% (Λx/d = 7) and Tu infinity = 20% (Λx/d = 7). In addition for the Tuinfinity = 20% turbulence level a second length scale was investigated, Λx/d = 11. The blowing ratio was varied from Msh = 0.8 to 1.5 for the showerhead and M ps = 0.3 to 1.8 for the pressure side. For each of the film cooling stations, experiments were performed investigating the effects of the mainstream-to-coolant and coolant-to-coolant interaction within mid-span, opposing jet, and endwall regions. For both the showerhead and pressure side coolant jets, the results indicate the influence of the interaction between the coolant jets and the interaction between the mainstream and coolant jet plays a large part in dictating the film cooling performance. |
