Effect of Film Hole Row Location on Film Effectiveness on a Gas Turbine Blade

Experiments were performed to study the effect of film hole row location on local film effectiveness distribution of a turbine blade model with air or CO₂ film injection. Tests were performed on a five-blade linear cascade at the chord Reynolds number of 3.0 × 10⁵ at the cascade inlet. A combination of turbulence grid and unsteady wake was used to create a higher free-stream turbulence level. The test blade had three rows of film holes in the leading edge region and two rows each on the pressure and suction surfaces. Film hole row locations were set by leaving the film holes at that row location open and covering the remaining rows. In addition, the additive nature of film cooling on the turbine blade model was examined by comparing the measured film effectiveness with the predicted effectiveness from the superposition method. Results show that injection from a different film hole row location provides a different effectiveness distribution on pressure and suction surfaces depending on local mainstream velocity and blade curvature. In most cases, the superposition method holds downstream of the last film hole row.