Particle trajectories near an airfoil with a film-cooled leading edge

Flow visualization techniques were developed and used to study particle trajectories near an airfoil with a film-cooled leading edge. The study was conducted to determine the size of particles which could be deflected by the cooling air jets. This is an important problem relevant to the development of high-temperature gas turbines which burn fuels which produce ash particles (e.g., coal). Experiments were performed on a large-scale airfoil in a low-speed wind tunnel utilizing uniformly sized DOP (Di-octyl phthalate) droplets and chopped streak photography to visualize particle trajectories. The results have been related to the flow in an engine through the use of Stokes parameter scaling. The results indicate that turbine airfoil leading-edge film cooling in a gas turbine engine may deflect particles up to at least 5.8-microns in diameter when the cooling air velocity is at least 0.67 times the approach velocity.