Turbulent Dispersion of Film Coolant and Hot Streaks in a Turbine Vane Cascade

: Magnetic resonance imaging techniques were used to investigate the 3D mean flow and turbulent mixing around a film cooled turbine vane. The overall objective was to understand the turbulent mixing in a complex flow and develop tools to determine the non uniform temperature distribution incident on a downstream turbine rotor. Magnetic resonance velocimetry provided the three component velocity distribution throughout a double passage vane cascade. The magnetic resonance concentration technique was used to measure the concentration of film coolant injected from trailing edge slots. The turbulent dispersion was strongly affected by vortex structures produced by film cooling slots. The passage vortex increased the spread of coolant near the end walls. Combustor hot streaks injected upstream of the cascade dispersed very slowly because turbulence is strongly suppressed by the acceleration through the cascade. A separate experiment examined the relevance of magnetic resonance experiments in water to turbine flows at high subsonic Mach numbers in air. Identical 3D mixing layer experiments were performed with low speed water mixing a chemical agent and high speed air flows mixing temperature. The dimensionless concentration/temperature profiles were nearly identical between the experiments.