Curvature Effects on a Turbine Blade Cooling Film

Abstract

Analysis of the equations governing the equilibrium conditions of a cool gas film injected along a curved wall in a hot gas stream shows that Archimedes type forces may either increase or decrease the cooling efficiency of the film, according to the value of the mass flow rate ratio, the temperature ratio of the flows and the sign of the curvature of the wall. Experiments have been performed to verify these predictions: in the case of a concave wall and relatively high mass flow rate ratios, a gain in performance has been obtained, if compared to the constant pressure flat plate; in the case of a convex wall, the cooling efficiency of the film is less than that of a film on a plate with the same pressure gradient, although it is still higher, for the same mass flow ratio than the efficiency of a film on a constant pressure plate.